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Which type of common congenital cataract rarely affects vision and appears as blue dots of varying shapes and sizes dispersed throughout the crystalline lens? A lamellar cataract A Mittendorf\'s dot A cerulean cataract **Your Answer** A persistent pupillary membrane **Explanation** A **cerulea...

Which type of common congenital cataract rarely affects vision and appears as blue dots of varying shapes and sizes dispersed throughout the crystalline lens? A lamellar cataract A Mittendorf\'s dot A cerulean cataract **Your Answer** A persistent pupillary membrane **Explanation** A **cerulean cataract** is also known as a \"***blue dot***\" cataract and is seen in the **lenticular periphery**, although it can be scattered throughout the crystalline lens. This type of congenital cataract is common and rarely affects visual acuity. A **Mittendorf\'s dot** is on the posterior lens and serves as a remnant of the hyaloid system, previously attached to the lens. During the **third month** of development, **mesenchymal cells** migrate between the lens epithelium and the corneal epithelium to form a transitory network of blood vessels anterior to the lens. This is the **pupillary membrane.** At **6 months** of development, the central blood vessels atrophy and the peripheral vessels increase their contribution to the **lesser circle of the iris.** By **8.5 months** of development, the central vessels fragment and disappear, although they can sometimes persist and appear as web-like projections attached to the iris surface; these are known as **persistent pupillary membrane strands.** A **lamellar cataract**, also known as a **zonular cataract**, is attributable to a fleeting exposure to some **type of cataract-inducing event or substance**. The cataract is limited to one or several layers of the lens, allowing the clinician to estimate during which period of the developmental period the exposure occurred. The fetal nucleus is commonly involved. This type of cataract can have an autosomal dominant inheritance pattern but is not always congenital in origin. What is the MOST common type of intraocular lens implant used to replace the crystalline lens during cataract surgery? Clear contact lens implant Posterior chamber lens implants **Your Answer** Iris-fixated lens implant Anterior chamber lens implant **Explanation** A **posterior chamber intraocular lens implant (PCIOL)** is the lens preferred by surgeons during cataract surgery. Most surgeons will attempt to place the PCIOL in front of the posterior capsule, which ideally is left intact post-surgery. This placement typically **offers the most natural vision post-surgery** because it is in the same location as the crystalline lens was previously, and it typically results in a lower complication rate compared to other lens options. **Anterior chamber lens implants** are used if the posterior capsule breaks or there is some other reason that a PCIOL cannot be used. **Iris-fixed lenses** are rarely used these days. A characteristic finding with these lenses is that this type of implant induces a square-shaped pupil. If you encounter an iris-fixed intraocular lens implant, you **CANNOT** dilate this patient because you may cause dislocation of the lens implant. Upon slit-lamp examination of your 76-year-old male patient, you observe the presence of an age-related cataract in which the lens is completely opaque, and the anterior capsule appears shrunken and wrinkled. What is the name of this type of cataract? Hypermature cataract **Your Answer** Morgagnian cataract Mature cataract Immature cataract **Explanation** When classifying the **maturity** of an age-related cataract, there are several factors to consider including the cloudiness of the lens, the appearance of the capsule, and the location of the lens nucleus. - **Immature cataracts** are those in which the lens is partially opaque. A mature cataract will present with a completely opaque crystalline lens. - **Hypermature cataracts** show wrinkling and shrinking of the anterior capsule due to leakage of water out of the lens, in addition to a completely opaque lens. - **Morgagnian cataracts** are *hypermature cataracts* in which there is significant liquefaction such that the nucleus of the crystalline lens begins to sink inferiorly. Which 2 of the following measurements are MOST important in calculating the intraocular lens power that will result in the desired post-operative refractive error following cataract surgery? **(Select 2)** Refractive error Axial length **Your Answer** Pachymetry Anterior chamber depth Corneal diameter Keratometry **Your Answer** **Explanation** To calculate the necessary **power of the intraocular lens implant** to be utilized during cataract surgery. This ensures that the patient\'s outcome will most closely match the desired post-operative refractive values. These measurements include **corneal keratometry** and the **anteroposterior dimension of the eye** (axial length). These values are most important due to the fact that the overall power of the eye is essentially dependent on corneal curvature and the lens, with the location of the retina as the image plane. Other measurements are often made with newer technological advances to better calculate the power of the intraocular lens. These include the anterior chamber depth, corneal white-to-white diameter, and an intraoperative wavefront aberrometry reading using a device called the **ORA**. Which of the following features is present in the crystalline lens to offset the occurrence of spherical aberrations that would otherwise naturally appear in this refracting element? A larger pupil size reduces spherical aberrations inherent in the crystalline lens The crystalline lens has a lower index of refraction near its edge compared to the index of refraction at its center **Your Answer** The radius of curvature of the anterior surface of the crystalline lens is shorter than the radius of curvature of the posterior surface The curvature of the crystalline lens is steeper in the periphery compared to the curvature of the lens at its center **Explanation** **Spherical aberrations** occur when parallel light rays that are incident towards the edge of an optical refracting element are bent more than those light rays that travel through the system closer to the center of the lens. This creates a smeared focal point because the peripheral light rays focus at a point in front of the main image. There are a few ways in which the human eye tries to offset this type of aberration. With respect to the cornea, this surface is an aspherical optical element, in which the periphery of the cornea is flatter than the center of the cornea, thereby weakening the focusing power of the peripheral cornea to reduce the amount of spherical aberration present. The crystalline lens is also vulnerable to spherical aberration; however, this refracting component has taken a different approach to control the aberration. Instead of relying on just the varying the curvature of its surface, the lens also varies its index of refraction. The index of refraction of the edge of the lens is lower (and therefore less powerful) than the index of refraction at its center. This is the lens\'s way of attempting to self-correct inherent spherical aberrations. A smaller pupil size is another way that the eye acts to reduce the spherical aberrations. In what order do the crystalline lens structures develop embryologically? Lens plate (placode), lens pit, lens vesicle, embryonic lens nucleus, lens capsule **Your Answer** Lens pit, lens vesicle, lens plate (placode), lens capsule, embryonic lens nucleus Lens plate (placode), lens capsule, lens vesicle, embryonic lens nucleus, lens pit Lens vesicle, lens pit, lens plate (placode), embryonic lens nucleus, lens capsule Lens plate (placode), lens vesicle, lens pit, lens capsule, embryonic lens nucleus **Explanation** The **lens plate** (placode forms from surface ectoderm adjacent to the optic vesicle, beginning around day 27 of development. The outer surface of the lens plate invaginates to form a lens pit which continues until it forms the lens vesicle. The lens vesicle separates from the surface ectoderm around day 33; it is a single layer of cells forming a hollow sphere. After the lens vesicle is formed, posterior epithelial cells become the primary lens fibers and form the embryonic lens nucleus at the center of the developing lens. The anterior cells stay in place currently, and the equatorial cells divide and elongate to form secondary lens fibers around the embryonic nucleus. The lens capsule is apparent at about 5 weeks; it originates from the basement membrane of the surface ectoderm and from secretions of the lens epithelium. Age-related cortical cataracts are MOST commonly initially found in which quadrant of the crystalline lens? Inferior-nasal **Your Answer** Inferior-temporal Superior-nasal Superior-temporal **Explanation** Cortical cataracts of the crystalline lens occur because of opacification of the mature fiber cells that lie close to the surface of the lens. They typically begin as small opacities of the lens periphery that may eventually spread around the circumference of the lens with age. These opacities can also extend centrally as well, potentially impinging on the visual axis and interfering with vision. Early stages of cortical cataracts most often occur in the inferior half of the lens periphery, with a predilection for the inferior-nasal quadrant specifically. Cortical lens opacities are best viewed with retroillumination through a dilated pupil during slit-lamp biomicroscopy. Which of the four Purkinje images is inverted? Ill Explanation There are four Purkinje images. The first image is caused by reflection from the anterior corneal surface and is the brightest of the images. The first image is roughly the same size as the object. The second Purkinje image is formed by the posterior surface of the cornea and almost coincides with the first Purkinje image. The third Purkinje image is the largest and is caused by reflection off of the anterior plane of the crystalline lens. The fourth Purkinje image is the smallest and is inverted, formed by reflection off of the posterior surface of the lens. Which of the following ocular conditions is the MOST common cause of secondary cataract formation? High myopia Acute angle closure Hereditary fundus dystrophies Chronic anterior uveitis Your Answer **Explanation** The most common cause of a **secondary cataract** (one in which a cataract develops because of some other primary disease) is **chronic anterior uveitis**. Long-standing intraocular inflammation can lead to prolonged breakdown of the blood-aqueous and/or blood-vitreous barrier. Additionally, patients with chronic inflammation are likely to be on long-term treatment with either systemic or topical corticosteroids; this is an important associated feature. **Acute angle closure** can cause small, grayish opacities that typically appear within the pupil area; these are a result of focal infarcts of the crystalline lens epithelium (known as **glaukomflecken**). **High myopia** has been shown to be associated with early onset of nuclear sclerosis and the formation of posterior subcapsular lenticular opacities. **Retinitis pigmentosa, gyrate atrophy, and Leber congenital amaurosis** are hereditary fundus dystrophies that have an association with posterior subcapsular cataracts. Which 2 of the following changes occur during accommodation? **(Select 2)** The posterior surface of the lens becomes significantly more curved The lens moves posteriorly The depth of the anterior chamber increases **The equatorial circumference of the lens decreases** **The introcular pressure decreases momentarily** **Explanation** During the process of **accommodation**, the anterior surface of the lens moves forward while the posterior surface stays same. This forward movement decreases the anterior chamber depth. The contraction of the ciliary muscle results in a transitory decrease in intraocular pressure. Lastly, because the lens becomes more spherical, the equatorial circumference of the lens decreases. The presence of small, iridescent, fleck-like opacities scattered throughout the crystalline lens (also known as \"Christmas tree cataracts\") are associated with which of the following systemic diseases? Myotonic dystrophy **Your Answer** Neurofibromatosis Wilson\'s disease Down\'s syndrome Atopic dermatitis **Explanation** **Myotonic dystrophy:** associated with multi-colored opacities known as \"Christmas tree cataracts\" (close to 90% of patients develop these cataracts) **Atopic dermatitis:** associated with shield-like, dense anterior subcapsular plaques **Neurofibromatosis:** associated with posterior subcapsular or posterior cortical cataracts **Wilson\'s disease:** associated with green \"sunflower\" cataracts **Down\'s syndrome:** low association with Cerulean or \"blue-dot\" cataracts Congenital cataracts can severely impair vision and lead to amblyopia if left untreated. What is the MOST common etiology of a congenital cataract? Metabolic disorder Infection Developmental disorder Genetic mutation **Your Answer** Birth trauma **Explanation** **Congenital cataracts** occur in about 1 in 3,000 live births and are found **bilaterally** in about 2/3 of cases. The most common cause of a congenital cataract has been associated with a **genetic mutation (\~25%)**-**autosomal dominant** but may be autosomal recessive or x-linked. Other **less common** etiologies of congenital cataracts include chromosomal abnormalities (Down syndrome), metabolic disorders (galactosemia), in-utero infection (rubella), or they may occur as part of a complex developmental disorder. The progression of cataracts causes a refractive shift towards which type of astigmatism? Oblique astigmatism Against-the-rule astigmatism **Your Answer** With-the-rule astigmatism Cataracts do not cause an astigmatic shift **Explanation** Cataracts induce a shift towards **against-the-rule astigmatism** due to a steepening of the crystalline lens in the horizontal meridian. A 56-year-old male patient reports that his vision constantly fluctuates with his current glasses\' prescription. Case history reveals poorly controlled diabetes mellitus with large variations in blood glucose levels. Which of the following diabetic related ocular changes is MOST likely responsible for his chief complaint? Swelling of the crystalline lens, leading to changes in its refractive index **Your Answer** Edema of the retina, leading to a decrease in visual acuity Swelling of the cornea, leading to changes in refractive error Elevated glucose levels, leading to cloudiness of the vitreous **Explanation** \_ Granular-appearing crystalline lens opacities that form due to posterior migration and swelling of lens epithelial cells e known as which of the following types of cataracts? Nuclear sclerotic cataracts Posterior capsular pacifications Posterior sutural cataracts Cortical cataracts Posterior polar cataracts Posterior subcapsular cataracts Your Answer Explanation Posterior subcapsular cataracts (PSCs) are lens opacities that form in front of the posterior lens capsule, typically presenting with a granular appearance on retroillumination during slit-lamp examination. PSCs develop as a result of abnormal migration of lens epithelial cells that form a cluster of swollen cells at the posterior region of the lens. Light scatter from these types of opacities is particularly disabling because the scatter tends to be located near the visual axis. Which of the following describes a yellowing or browning discoloration of the crystalline lens nucleus? ♥ Brunescence Your Answer Nuclear spoking Cortical spoking Posterior subcapsular pacification Explanation Cataracts are classified by the zone of the lens that is opacified. Brunescence indicates yellowing or browning of the lens nucleus; it is a central opacity in the nucleus that enlarges over time indicating hardening of the lens. Cortical spokes are small opacities at the lens periphery that eventually enlarge toward the center. What is the correct accommodative sequence that occurs when a person focuses on a near object? Relaxation of ciliary muscles → increased tension on the zonules → lens alters shape to become more spherical and thicker in the axial region → dioptric power increases Relaxation of ciliary muscles → decreased tension on the zonules → lens alters shape to become more spherical and thicker in the axial region → dioptric power increases Contraction of ciliary muscles → decreased tension on the zonules → lens alters shape to become more spherical and thicker in the axial region → dioptric power increases Your Answer Contraction of ciliary muscles → increased tension on the zonules → lens alters shape to become more spherical and thicker in the axial region → dioptric power increases Explanation The lens alters its shape to focus on images depending on their location in space. When we need to visualize an image up close, the ciliary muscle contracts which decreases the tension on the zonules, causing the lens to become more spherically shaped and steeper in curvature, thereby increasing its dioptric power. The opposite holds true for viewing of a distant image. Looking far away causes relaxation of the ciliary muscles, increasing tension on the zonules allowing for the lens to become more elliptical and flatter in curvature, thereby decreasing its power. Your 43-year-old male patient reports a gradual decrease in vision over the past year that tends to worsen when he is reading or in bright lighting conditions. Slit-lamp examination reveals a granular, plaque-like cataract that appears black on retroillumination. What is the MOST likely diagnosis for this patient? Posterior subcapsular cataract Your Answer Cortical cataract Mature cataract Nuclear sclerotic cataract Explanation Posterior subcapsular cataracts occur just in front of the posterior capsule and typically present as a granulated or vacuolated opacity that can be best viewed with an obliquely oriented parallel-piped light beam on slit-lamp biomicroscopy. On retroillumination, this type of cataract appears as a black plaque located deep within the lens (it has the same appearance on retinoscopy). Patients presenting with this type of cataract commonly complain of decreased vision, even in mild cases, due to the location of the opacities occurring at the nodal point of the eye. Near vision and vision under bright light conditions are typically the most affected due to pupil miosis that occurs in these situations. Posterior subcapsular cataracts have a strong association with long-term use of systemic or topical corticosteroids. Cortical cataracts typically present as wedge-shaped or radial spoke-like opacities that can occur in the anterior, posterior, or equatorial cortex of the crystalline lens. These patients more commonly complain of problems with glare due to the scattering of light from these opacities. A nuclear sclerotic cataract is characterized by an early yellowing of the crystalline lens nucleus due to the deposition of urochrome pigment; it eventually appears brownish in color in later stages. It is best viewed with an oblique light beam on slit-lamp evaluation (vs. retroillumination). A mature cataract is a completely opacified crystalline lens that commonly appears white in color. Which of the following conditions places a patient at a higher risk of posterior capsular rupture during cataract surgery and/or dislocation of the intraocular lens implant after surgery? Systemic lupus erythematosus Multiple sclerosis Pseudoefoliation syndrome Your Answer Primary open angle glaucoma Explanation A patient with pseudoexfoliation syndrome, despite removal of the cataract, can still produce pseudoexfoliative material, which can further weaken the lenticular zonules. The continued weakening of zonules can lead to dislocation of the intraocular lens implant, as the IOL is usually placed in the \"bag\" with the posterior capsule still intact. Patients with this condition are also at an increased risk for rupture of the posterior capsule. A patient with pseudoexfoliation syndrome and iridodonesis will commonly have a capsular tension ring inserted at the time of cataract removal surgery. Frequently, the IOL will either be placed in the sulcus or sutured in place to prevent dislocation. Patients with pseudoexfoliation syndrome are typically referred for cataract surgery as soon as the cataracts become clinically significant in order to minimize complications associated with the removal of dense cataracts. Although patients with multiple sclerosis and lupus may experience ocular complications associated with these conditions or their treatments, they are not at a higher risk of lens dislocation or posterior capsular rupture during phacoemulsification. Pseudoexfoliation syndrome: pathological manifestations of relevance to intraocular surgery. Patients with a history of homocystinuria are MOST likely to experience crystalline lens subluxation in which of the following directions? Downward and outward Upward and outward Upward and inward Downward and inward Your Answer Explanation Common ocular sequelae that have been associated with a diagnosis of homocystinuria include ectopia lentis (bilateral crystalline lens subluxation), retinal detachment, and secondary glaucoma. In most cases of ectopia lentis associated with homocystinuria, the lens is more likely to be displaced downward and inward (as compared to upward and outward in Marfan\'s syndrome). Additionally, in homocystinuria, the lens zonules are markedly abnormal, the lens does not accommodate, and up to 1/3 of the cases of lens subluxation eventually completely dislocate into the vitreous or anterior chamber. Due to the severity of systemic and cardiovascular complications associated with homocystinuria (thrombosis and occlusion), patients presenting with ectopia lentis should be screened for this disease using the sodium nitroprusside test to measure homocysteine in the urine. Which of the following anatomical changes is NOT thought to occur with the development of presbyopia? Anterior crystalline lens capsule thickens ciliary muscle contractile forces decrease Your Answer Equivalent refractive index of the crystalline lens decreases Anterior chamber depth decreases Crystalline lens axial thickness increases Explanation Although the human ciliary muscle shows a loss of muscle fibers and an increase in connective tissue with age, studies have suggested that ciliary muscle contractile forces do not actually decrease with age. Strikingly, ciliary muscle forces may actually increase and reach their maximum near the point in which presbyopia begins to manifest. Berger\'s space is created by an interval between which two structures? The anterior face of the lens and the posterior surface of the iris The posterior surface of the cornea and the anterior face of the iris The posterior face of the lens and the anterior vitreous Your Answer The equator of the lens and the ciliary body Explanation Berger\'s space is created by the separation between the posterior face of the lens and the anterior face of the vitreous. The space between the equator of the lens and the ciliary body is known as the circumlental space. An 81-year-old female patient presents with a chief complaint of blurred vision and glare at night. Slit-lamp examination reveals fibrosis on the posterior surface of her intraocular lens implant. What is her diagnosis? Anterior capsular contraction Posterior polar cataract Posterior capsular opacification Your Answer Posterior subcapsular cataract Explanation The most common late complication (of uncomplicated cataract surgery) is visually significant posterior capsular pacification. This finding commonly causes complaints of decreased vision, impaired contrast sensitivity, glare, and in some cases, monocular diplopia. Elschnig pearls are a typical finding that appear as vacuolated clusters on the back surface of the lens implant. They are a result of migration and proliferation of residual equatorial lens epithelial cells along the posterior capsule. In addition to Elschnig pearls, capsular fibrosis is another common type of posterior capsular pacification that is due to fibrous metaplasia of epithelial cells. It is less common than Elschnig pearls but usually appears earlier. Posterior subcapsular cataracts and posterior polar cataracts only occur in the natural crystalline lens. Anterior capsular contraction is a post-operative complication that typically occurs several weeks after cataract surgery. Contraction and fibrosis of the anterior capsule can continue to progress and affect visual acuity. Which 3 of the following layers of the retina are pushed aside at the foveola? (Select 3) The inner nuclear layer Your Answer The photoreceptors The inner plexiform layer Your Answer The retinal pigment epithelium The internal limiting membrane The ganglion cell layer Your Answer Explanation In order to maximize cone function and acuity, the fovea displays certain structural differences when compared to the rest of the retina. At the fovea, the bipolar and ganglion cell layers are pushed aside. At the foveola, the inner plexiform layer, the inner nuclear layer, the ganglion cell layer, and the nerve fiber layer are all pushed aside. Essentially, at the center of the foveola, the cones, internal limiting membrane, and the retinal pigment epithelium are the only layers that are present. Remember, the fovea is also avascular. Which 2 of the following statements are TRUE in regards to the peripheral retinal structures found at the ora serrata? (Select 2) VOral bays are the scalloped edges of the pars plana that reside between the dentate processes Your Answer Oral bays are the scalloped edges of the peripheral retina that reside between the dentate processes Dentate processes are the teeth-like extensions of the peripheral retina that course onto the pars plana Your Answer Dentate processes are the teeth-like extensions of the pars plana that course onto the peripheral retina Explanation The ora serrata is the ocular landmark of the junction between the peripheral retina and the pars plana of the ciliary body. The ora serrata is characterized by certain observable features, including oral bays and dentate processes. Dentate processes are the teeth-like extensions of the peripheral retina that extend onto the pars plana. They are more marked in the nasal periphery as compared to the temporal ora serrata. Oral bays are the scalloped edges of the pars plana epithelium that reside between the dentate processes of the retina. Which of the following layers of the retina represents Henle\'s fiber layer in the macular region? Inner plexiform layer Outer limiting membrane Inner nuclear layer Outer plexiform layer Your Answer Inner limiting membrane Outer nuclear layer Explanation In order to maximize cone function and acuity, the fovea displays certain structural differences when compared to the rest of the retina. At the fovea, the bipolar and ganglion cell layers are pushed aside. At the foveola, the inner plexiform layer, inner nuclear layer, ganglion cell layer, and the nerve fiber layer are all pushed aside. Essentially, this leaves the retinal pigment epithelium, internal limiting membrane, cone photoreceptors, and the outer plexiform layer. In the macula, the outer plexiform layer is known as Henle\'s fiber layer. It is comprised of an oblique and radially oriented arrangement of axons of cone photoreceptors. Which of the following electrodiagnostic tests is primarily used for the evaluation of ganglion cells within the retina? Full-field electroretinogram (ffERG) Visual evoked potential (VEP) Pattern electroretinogram (pERG) Your Answer Multifocal electroretinogram (mfERG) Electro-oculogram (EOG) Explanation pERG- this is primarily used for evaluation of ganglion cells in the central retina. A corneal electrode is used to record the response to checkerboard-pattern stimuli of an undilated eye. VEP- this is an electrophysiological signal recorded at the occipital lobe in response to a checkerboard pattern (for pattern VEP) or flash stimulation (for flash VEP) presented in the central visual field of an undilated patient. fERG- this test provides a topographic map of the central retina function for the cone system with a diameter of 40-50 degrees. The signals are detected with a corneal electrode on a dilated eye. The mfERG waveforms mainly represent photoreceptor and bipolar cell responses. Amplitude and time of the positive response (P1) are most commonly used for analysis. ffERG- this is a mass retinal response elicited by stimulating dilated eyes with flashes of light from a Ganzfeld stimulator. It is routinely recorded with corneal electrodes. It allows for evaluation of the cone and rod systems and can delineate photoreceptor and bipolar cell contributions. The responses are evaluated based on the morphology and other measurable parameters of waveform components. EOG- this evaluates RPE function under dark and light phases. Responses decrease with dark adaptation and then increase with light adaptation. Reduced Arden ratio (the light peak/dark trough ratio) indicates RPE dysfunction. Upon examining your 51-year-old male patient, you observe what appears to be a subtle retinal nerve fiber layer defect. Which of the following colored filters will allow for enhanced visualization of this tissue? Green Your Answer Yellow Blue Red Explanation Localized damage to the retinal nerve fiber layer typically presents as a slit or wedge defect emanating from the margin of the optic disc. The retinal nerve fiber layer is best visualized utilizing a green (red-free) filter during fundus evaluation with the slit-lamp biomicroscope. Red-free filters enhance contrast and allow for a better view of subtle nerve fiber layer defects. Which of the following retinal findings is NOT characteristic of severe non-proliferative diabetic retinopathy? At least 1 quadrant of prominent intraretinal microvascular abnormalities At least 20 intraretinal hemorrhages in each quadrant At least 2 quadrants of venous beading At least 2 quadrants containing cotton wool spots Your Answer Explanation A diagnosis of severe non-proliferative diabetic retinopathy (NPDR) includes the presence of any of the following retinal observations in the absence of proliferative retinopathy: \- 20 intraretinal hemorrhages in each quadrant \- 2 quadrants of venous beading \- 1 quadrant of prominent intraretinal microvascular abnormalities (IRMA) The presence of cotton wool spots is a characteristic feature of diabetic retinopathy but is not involved in the classification of the severity of NPDR. The presence of which of the following retinal characteristics will result in a corresponding area of hyperfluorescence during fluorescein angiography? Congenital hypertrophy of the RPE Intraretinal hemorrhage Lipofuscin Hard exudates Choroidal nevus Pigment epithelial detachment Your Answer Explanation Areas of hyperfluorescence that appear during fluorescein angiography occur due to either an absolute increase in the amount of fluorescein in the retinal tissues, or as a result of enhanced visualization of a normal quantity of fluorescein in the fundus. Conditions that can lead to hyperfluorescence include leakage of dye from abnormal choroidal vasculature (such as a choroidal neovascular membrane), abnormal retinal neovascularization (as in proliferative diabetic retinopathy), or breakdown of the inner blood-retinal barrier (cystoid macular edema). Hyperflourescence also occurs as a result of pooling of fluorescein secondary to breakdown of the outer blood-retinal barrier in such conditions as central serous retinopathy and pigment epithelial detachments. A transmission (or window) defect caused by an absence or atrophy of the RPE results in unmasking of normal background choroidal fluorescence, leading to the appearance of hyperfluorescent areas. Hypofluorescent regions on fluorescein angiography are due to either obstruction (masking) of normal density of fluorescein in the retinal tissue (blood, hard exudates, increased density of RPE, or choroidal nevi), or inadequate perfusion of the retinal tissue (vascular occlusion, or loss of the vascular bed). You have a patient who is currently taking chloroquine for rheumatoid arthritis. Upon dilated fundus examination, you notice what appears to be early changes suggestive of retinopathy in the macular region of both eyes and decide to perform an electrooculogram. If the light peak of the right eye measures 740 uV and the dark trough measures 420 uV, what is the Arden ratio, and what can you conclude from this finding? 0.55; normal 0.55; abnormal 1.76; abnormal Your Answer 1.76; normal Explanation An electroculogram uses the electrically positive cornea and electrically negative back of the eye to measure the standing potential between the two regions. The readings reflect the activity and integrity of the photoreceptors and retinal pigment epithelium; therefore, retinal diseases that affect this area will lead to a reduction in the signal produced. The test is performed in both light and dark adapted states. Interpretation of the results involves measuring the maximal height of the potential in the light and maximal trough of the potential in the dark. The Arden ratio can then be calculated by dividing the light peak value by the dark trough value. Normal values are above 1.80. For the above case, the light peak is 7.4 and dark trough is 4.2. 7.4/4.2 = 1.76 1.76 is below 1.80; therefore the ratio may be considered abnormal. Your 68-year-old male patient presents with an idiopathic macular hole in his left eye. He asks what the chances are that a macular hole will also develop in his right eye. What percentage of patients typically develop a macular hole in their fellow eye as well? 0-10% 20-30% 40-50% 10-20% Your Answer 30-40% 50-60% Explanation The following represents the most common profile of a patient presenting with a macular hole: \- Most commonly idiopathic in otherwise healthy individuals \- Typically occurs in the 6th or 7th decade of life \- Women are more affected than men (2:1) \- 10-20% of patients develop bilateral macular holes Your 65-year-old female patient has been diagnosed with a macular hole in her left eye, and shows vitreomacular traction upon OCT evaluation of her right eye. Which of the following BEST describes the diagnosis of her right eye\'s findings? Epiretinal membrane Macular pseudo hole Stage O macular hole Your Answer Stage 1 macular hole Explanation Stage O macular hole: \- Abnormal vitreofoveal traction (usually observed only by OCT) in the fellow eye of a patient with a macular hole \- This eye has an elevated risk of macular hole formation with this presentation (43%), as compared to those without this abnormal vitreomacular appearance, in which the risk is very low for subsequent hole formation In addition to decreasing intraocular pressure in patients with acute angle closure, oral acetazolamide may also be utilized in patients presenting with which of the following ocular conditions? Retinal detachment Corneal edema Vitritis Conjunctivitis Macular edema Your Answer Explanation Oral acetazolamide can also be used in cases of macular edema secondary to inflammatory conditions, particularly when topical non-steroidal anti-inflammatory medications (NSAIDs) and corticosteroids fail. A patient is concerned with an acute reduction of visual acuity in his right eye. You correctly diagnose central serous retinopathy, and confirm your diagnosis with optical coherence tomography (OCT). What is the standard treatment protocol for this condition? Refer for cryotherapy of the retina Refer for intravitreal steroid injection Refer for laser treatment of the retina Treat the patient with prism as he is likely to develop diplopia Monitor monthly for resolution Your Answer Explanation CSR is more commonly seen in middle-aged males under high-stress, who are very anxious, or have type A personalities. This condition causes fluid to leak from the choriocapillaries into the subretinal area, causing a serous detachment of the neurosensory retina. There is usually an associated loss of the foveal reflex, a hyperopic shift, a potential relative scotoma, and metamorphopsia. Flourescein angiography will reveal hyperfluorescence that appears like a smoke-stack. Evaluation of the posterior pole will typically display a blister-like elevation of the neurosensory retina. Patients with this condition are typically monitored monthly and intervention is rarely required, as most cases of CSR will resolve within roughly 6 months. Which of the following lists of retinal structures is correctly ordered from most central (smallest diameter) to the most peripheral (largest diameter)? Fovea → foveola → parafoveal area → perifoveal area Foveola → fovea → parafoveal area → perifoveal area Your Answer Foveola → fovea → perifoveal area → parafoveal area Fovea → foveola → perifoveal area → parafoveal area Explanation The foveola is about 0.35 mm in diameter and contains the densest population of cones with the smallest cross-sectional diameter of all photoreceptors. The fovea centralis is a shallow depression in the center of the macular region. It is about 1.5 mm diameter. The annular zone around the fovea contains an inner paratoveal area that is comprised of retinal bipolar cells and ganglion cells, and has about a 2 mm diameter. Outside of the parafoveal region is the perifoveal area that contains ganglion cells and has a diameter of about Which of the following types of laser technologies depends on the birefringence properties of the retinal nerve fiber layer in order to measure its thickness? Optical coherence tomography Scanning laser plarimetry Your Answer Scanning laser ophthalmoscopy Confocal scanning laser tomography Explanation Birefringence is the splitting of a light ray (or wave) into two components as it passes through an anisotropic material. In an anisotropic material, the index of refraction is dependent on the direction of light within the material. There are several components of the eye that can be considered birefringent, including the cornea, lens, and retinal nerve fiber layer (RNFL). The basis of measuring RNFL thickness in a scanning laser polarimeter (such as the GDx VCC) is due to the birefringent properties of the RNFL. The RNFL is composed of highly ordered parallel axon bundles that contain microtubules and other cylindrical intracellular organelles that have a diameter smaller than the wavelength of light. This highly ordered structure is the source of birefringence of the RNFL. When light waves from the instrument are incident on the birefringent RNFL, the waves are split into two different components that travel at different velocities, creating a phase shift. This phase shift is also known as retardation and is directly proportional to the thickness of the RNFL. Because the cornea and lens are also considered birefringent structures, this instrument must compensate for the anterior segment birefringence in order to produce an accurate measure of the RNFL thickness. Which of the following types of blood vessels offer the greatest resistance and the lowest flow rate? Ophthalmic artery Retinal vessels Your Answer Choroidal vessels Carotid artery Explanation Blood vessels of the retina are very small and as such offer high resistance and low flow rate (about 1.7 ml/min/gm) due to their small lumen. In contrast, choroidal vessels are larger and have lower resistance and a higher flow rate (roughly 19 ml/min/gm). The ophthalmic and carotid arteries are even larger than the retinal and choroidal vessels, leading to even higher flow rates. In approximately what percentage of patients presenting with a stage 1 macular hole will the hole spontaneously resolve without treatment? 10% 20% 50% Your Answer 30% 40% **Explanation** **50% of stage 1 macular holes** will resolve following spontaneous vitreomacular separation; these are therefore seen and not typically treated surgically **Stage 1 macular hole:** \- Patient is typically asymptomatic with both eyes open (difficult to detect and diagnose), but when symptoms are present, patients usually note decreased acuity and/or distorted vision \- Also known as pre-macular holes, macular cysts, or involutional macular thinning \- In this stage, no true neuroretinal defect is present, and the photoreceptor layer is intact \- There is further division of stage 1 macular holes into stage la, during which there is a small central yellow spot that can be seen with ophthalmoscopy, along with flattening of the macular contour; and stage 1b, wherein a yellow ring can be seen in the foveal area Which 3 of the following statements BEST represent the phenomena responsible for the dark appearance of the fovea during fluorescein angiography imaging? (Select 3) An increased density of carotenes in the foveal region The absence of retinal blood vessels in the center of the fovea Your Answer The retinal pigment epithelial cells in the foveal region are larger and contain more melanin Your Answer The retinal pigment epithelial cells in the foveal region are smaller and more densely packed The absence of choroidal blood vessels in the center of the fovea An increased density of xanthophyll in the foveal regionYour Answer Explanation In a normal fluorescein angiography image, the dark appearance of the fovea occurs as a result of three phenomena: \- The center of the fovea does not contain retinal blood vessels (foveal avascular zone) \- The choroid below the fovea does contain a network of blood vessels that fills with fluorescein in the early phase; however, there is blockage of this background choroidal fluorescence due to the increased density of xanthophyll in the foveal region \- Additionally, background choroidal fluorescence is blocked due to the retinal pigment epithelial (RPE) cells in the fovea, which contain more melanin and are larger than RPE cells elsewhere in the retina Which 3 of the following conditions are associated with a higher incidence of developing a posterior vitreous detachment? (Select 3) Hypertension Keratoconus Intraocular surgery Your Answer Diabetes Your Answer Anisometropic hyperopia High myopia Your Answer Explanation Syneresis and liquification of the vitreous are part of the normal aging process, but they may also cause a posterior vitreous detachment (PVD). PVDs can occur earlier in one\'s life if something speeds up the process of vitreal aging. These conditions may include myopia, trauma, diabetes, intraocular surgery, intraocular inflammation, and vitreal hemorrhages. Which 3 of the following characteristics are considered the MOST common risk factors for the development of a retinal detachment? (Select 3) Aphakia Your Answer Glaucoma Hyperopia V Myopia Your Answer V Ocular trauma Your Answer Explanation According to the American Optometric Association, the most common risk factors for the development of a retinal detachment are myopia (40-55%), aphakia (30-40%), and ocular trauma (10-20%). Trauma significantly increases the risk of detachment because retinal tears or dialysis can occur, both of which can lead to the formation of a retinal detachment. Myopia greater than 8 diopters, or patients with an axial length greater than 24 mm, have been shown to be at an increased risk for retinal detachments as well. Studies have also shown a greater incidence of retinal detachments in patients who are aphakic; this typically occurs within the first year following surgery. It is presumed that this may be correlated to posterior vitreous detachments, which commonly occur during this period. Which of the following ocular diseases represents the MOST common cause of irreversible vision loss in the United States involving individuals over the age of 50? Glaucoma VAge-related macular degeneration Your Answer Cataracts Diabetic retinopathy Hypertensive retinopathy Explanation The most common cause of vision loss in individuals over the age of 50 (in developed countries) is age-related macular degeneration (AMD). In the United States, at least 10% of patients between the ages of 65 and 75 have some impairment of visual acuity that can be attributed to AMD. Furthermore, of individuals over the age of 75, 30% have some degree of central vision loss as a result of AMD. These statistics show that the prevalence of severe visual loss increases with age. How many photons are necessary to stimulate a rod photoreceptor? 1 photon Your Answer 50 photons 10 photons 100 photons Explanation One photon is all that is required to stimulate a rod cell. The photon is absorbed by rhodopsin located in the disc membrane of the outer segment, causing a cascade of events. However, in order for a stimulus to be detected, around 10 photons must be experienced. This is can occur either by spatial summation or by temporal summation. What is the term for the funnel-shaped region anterior to the optic disc that represents the posterior termination of Cloquet\'s canal? Area of Martegiani Your Answer Erggelet\'s space Berger\'s space Hyaloid space Patellar fossa Explanation The area of Martegiani signifies the funnel-shaped dilation surrounding the optic disc; it represents the posterior termination of Cloquet\'s canal (also known as the hyaloid canal). Berger\'s space is an area between that anterior face of the vitreous body and the posterior lens capsule. It represents the anterior termination of Cloquet\'s canal. It is also known as Erggelet\'s space. The patellar fossa characterizes the anterior depression of the vitreous body in which the crystalline lens resides. Which of the following is NOT an indication of wet age-related macular degeneration (ARMD)? Classic choroidal neovascular membrane (CNVM) Submacular hemorrhage Drusenoid pigment epithelial detachment Your Answer Exudates Occult choroidal neovascular membrane (CNVM) Explanation Drusenoid pigment epithelial detachments are a sign of dry ARMD, as there is no leakage involved. A detachment of the retinal pigment epithelium occurs due to the thickness of the soft confluent drusen. The drusen push and displace the retinal pigment epithelium. The internal limiting membrane of the retina is formed by a combination of glial cell processes and which of the following other cell types? Amacrine cells Bipolar cells Muller cells Your Answer Horizontal cells Explanation The internal limiting membrane is formed by radial feet processes of Muller cells, along with other glial cell constituents. Muller cell processes extend throughout the length of the retina, except for the retinal pigment epithelium. Their cell bodies are found in the inner nuclear layer. Muller cells, along with segments of the photoreceptors, create tight junctions and serve to form the external limiting membrane. At which location of the retina is the peak density of rod photoreceptors located? 4.5 mm from the foveal pit Your Answer 1.0 mm from the foveal pit 0.5 mm from the foveal pit 6.0 mm from the foveal pit 2.5 mm from the foveal pit Explanation In the human fovea there are no rod photoreceptors present; cones are the only photoreceptors in this area, and they are perfectly arranged in a hexagonal mosaic pattern. Outside of the foveal region, the rod photoreceptors are introduced, breaking up this tight hexagonal cone packing. However, this architecture is still very organized, as cones are rather evenly spaced around the rods. Cone density rapidly falls outside of the fovea and remains at a steady density in the peripheral retina. As the cone density rapidly declines, the rod photoreceptor density quickly increases to a peak density in a ring around the fovea (also known as the \"rod ring\"). This is located about 4.5 mm from the center of the fovea (or 18 degrees from the foveal pit). Which of the following molecules acts as a second messenger in the retina AND is involved in the phototransduction cascade? Inositol-triphosphate V CGMP Your Answer Nitric oxide CAMP Explanation Signal transduction in the retina occurs as follows: Light → activates rhodopsin → activates G protein (in rod outer segment disc called transducin) → transducin → activates phosphodiesterase, which lowers cGMP levels. Decreased levels of GMP causes sodium and calcium channels to close, resulting in hyperpolarization of the membrane. Because the membrane is now hyperpolarized, the current flow to bipolar and ganglion cells becomes interrupted; this signals the brain and results in the perception of light. Which of the following retinal structures represents the WEAKEST attachment site for the posterior cortical vitreous? Retinal blood vessels Your Answer Vitreous base Optic nerve head Macula Explanation The vitreous body is normally attached posteriorly to several structures of the eye including the peripheral retinal blood vessels, macula, optic nerve head, and the vitreous base (which straddles the ora serrata). As the vitreous degenerates with age, a posterior vitreous detachment is a common observation that occurs as a result of the separation of the posterior hyaloid membrane from the internal limiting membrane of the retina; this can occur at any point posterior to the vitreous base. The most common location of a posterior vitreous detachment is at the site of vitreopapillary separation. The strongest area of attachment of the vitreous is at the ora serrata (vitreous base), followed by the optic nerve head. The adhesion in the area of the fovea is fairly weak, while the weakest attachment sites of the vitreous body are along the peripheral retinal blood vessels. Flame hemorrhages that are characteristic of hypertensive retinopathy occur in which layer of the retina? The inner nuclear layer The nerve fiber layer Your Answer The ganglion cell layer The retinal pigment epithelium Explanation Flame hemorrhages occur at the level of the nerve fiber layer and stem from blood loss from the inner capillary network of the retinal vasculature. These types of hemorrhages are commonly seen in hypertensive patients, vein occlusions, and optic neuropathies such as papilledema. The characteristic flame shape occurs because the blood will take the path of least resistance and follow the structure of the nerve fiber layer. Which 3 of the following types of retinal cells undergo a \"graded\" potential (vs. an action potential)? (Select 3) Horizontal cells Your Answer Bipolar cells Your Answer Amacrine cells V Photoreceptor cells Your Answer Ganglion cells Explanation Certain cells of the retina, including bipolar cells, horizontal cells, and photoreceptor cells (rods and cones) do not generate action potentials like most of the rest of the neurons in the human body. Neurological signaling in these types of cells occurs via graded changes in their membrane potential. Graded potentials allow a greater number of distinct signal amplitudes as compared to single large spikes. This is in contrast to the amacrine and ganglion cells of the retina, both of which produce action potentials. Which of the following ocular conditions is NOT considered a \"white dot syndrome\"? Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) Polypoidal choroidal vasculopathy Your Answer Serpiginous choroidopathy Birdshot retinochoroidopathy Explanation White dot syndromes (also known as primary idiopathic inflammatory choriocapillaropathies) are ocular inflammatory conditions that are characterized by the presence of white dots on the fundus. The most common visual symptoms of patients presenting with these diseases include blurred vision and visual field loss. The exact etiology of these ocular conditions is unknown; however, some investigators believe there to be a connection with bacterial and viral infections, genetic predispositions, and/or autoimmune associations. Classically recognized white dot syndromes include: acute posterior multifocal placoid pigment epitheliopathy (APMPPE), birdshot retinochoroidopathy, multiple evanescent white dot syndrome (MEWDS), serpiginous choroiditis, punctate inner choroidopathy (PIC), and multifocal choroiditis with panuveitis (MCP). Polypoidal choroidal vasculopathy is an idiopathic choroidal vascular disease that is characterized by a dilated network of choroidal blood vessels that have multiple terminal aneurysmal protuberances (in a polypoidal appearing fashion). This condition is not considered a \"white dot syndrome.\" Which of the following lifestyle choices possesses the HIGHEST risk for the development of macular degeneration? Increased ultraviolet light exposure Smoking Your Answer Excessive alcohol consumption Increased body mass index Explanation Research has demonstrated that lifestyle choices such as smoking, a high body mass index, increased ultraviolet exposure, and a poor diet all increase the chances of developing macular degeneration. Smoking alone increases the risk of developing macular degeneration up to 16 to 20 times. The main risk factor for the development of age-related macular degeneration (AMD) is increasing age. Other important risk factors include positive family history of AMD, Caucasian race, and the presence of age-related maculopathy (especially when associated with soft drusen). Which 3 of the following ophthalmologic manifestations are commonly associated with malignant hypertension? (Select 3) Acute angle closure Chorioretinal retinal atrophy Flame-shaped hemorrhages Your Answer Hollenhorst plaques Papilledema Cotton wool spots Your Answer Your Answer Explanation A sudden significant rise in blood pressure can damage the delicate retinal vessel walls; this can lead to flame-shaped hemorrhages and/or infarction of the nerve fiber layer, producing cotton wool spots. In the most severe and long-lasting cases, papilledema can ensue. On the other hand, Hollenhorst plaques reflect an embolic phenomenon from thrombotic disease, usually from the carotid artery. Acute angle closure and chorioretinal atrophy are not associated with malignant hypertension. Which of the following represents the MOST common cause of a rhegmatogenous retinal detachment in adults? Trauma Previous cataract surgery Choroidal melanoma Diabetic retinopathy Lattice retinal degeneration Posterior vitreous detachment Your Answer Explanation Rhegmatogenous retinal detachments are caused by a full-thickness retinal break in which liquid vitreous is allowed to enter the subretinal space and separate the neuroretina from the retinal pigment epithelium (RPE). The most common cause of a rhegmatogenous detachment is a retinal tear at the site of vitreoretinal adhesion during the advancement of a posterior vitreous detachment (PVD). Factors that may put patients at higher risk of developing this condition include the presence of lattice degeneration and previous intraocular surgery. Tractional retinal detachments are not associated with retinal breaks but occur due to tractional forces secondary to a diseased vitreous. The most common cause of tractional retinal detachments is proliferative diabetic retinopathy. Occasionally, patients with a tractional retinal detachment can develop retinal tears, leading to a combined tractional/rhegmatogenous detachment. Exudative retinal detachments occur as a result of breakdown of the blood-retinal barriers or the RPE due to choroidal or retinal disease. Common causes of this type of detachment include choroidal tumors and posterior scleritis. Which of the following structures is NOT found in cone photoreceptors? Mitochondria Free-floating discs in the outer segment Your Answer A synaptic terminal Ciliary processes An inner segment Explanation Cones and rods possess outer segments that consist of stacks of disc-like structures containing photopigment; however, the discs of cones are not free-floating. The discs of cones remain attached as they migrate outwards. It was previously thought that only rods possessed a cilium, but this has been proven to be inaccurate. Both rods and cones possess ciliary processes, inner segments, mitochondria, and synaptic terminals. The synaptic terminals of rods differ in their morphology from cones in that they are slightly smaller and rounder and are called spherules, while cones display a larger and flatter terminal called a pedicle. AOWC LUIICCL Which of the following structures is NOT found in cone photoreceptors? Mitochondria Free-floating discs in the outer segment Your Answer A synaptic terminal Ciliary processes An inner segment Explanation Cones and rods possess outer segments that consist of stacks of disc-like structures containing photopigment; however, the discs of cones are not free-floating. The discs of cones remain attached as they migrate outwards. It was previously thought that only rods possessed a cilium, but this has been proven to be inaccurate. Both rods and cones possess ciliary processes, inner segments, mitochondria, and synaptic terminals. The synaptic terminals of rods differ in their morphology from cones in that they are slightly smaller and rounder and are called spherules, while cones display a larger and flatter terminal called a pedicle. Central serous retinopathy (CSR) is associated with an acute decrease in vision, along with central distortion. This condition usually occurs unilaterally. Which gender and age group tends to have the highest incidence of CSR? Females; ages 20-40 Males; ages 30-50 Your Answer Males; ages 50-70 Females; ages 10-20 Explanation CSR is more commonly seen in middle-aged males under high-stress, with high anxiety, or with type A personalities. This condition causes fluid to leak from the choriocapillaries into the subretinal area, causing a serous detachment of the neurosensory retina. There is usually an associated loss of the foveal reflex, a hyperopic shift, a potential relative scotoma, and metamorphopsia. Flourescein angiography will reveal hyperfluorescence that appears like a smoke-stack. Evaluation of the posterior pole will typically display a blister-like elevation of the neurosensory retina. Patients with this condition should be monitored monthly, and intervention is rarely required as most cases of CSR will resolve within roughly 6 months. Although controversial, it has been purported that supplementation of vitamin A is important in the management of retinitis pigmentosa. Which of the following agents, when taken in excess amounts, may interfere with the uptake of Vitamin A? Vitamin E Your Answer Calcium Vitamin B12 Vitamin K Explanation Vitamin A plays an important role in vision, and it is currently believed that daily supplementation of 15,000 IU of Vitamin A may aid in decreasing the progression of retinitis pigmentosa. Research has demonstrated that taking increased levels of vitamin E simultaneously with higher doses of vitamin A may interfere with the uptake and distribution of vitamin A. Therefore, it is recommended that patients taking vitamin A for the management of retinitis pigmentosa avoid ingestion of higher amounts of vitamin E. You decide to perform a Watzke-Allen test on your 67-year-old female patient whom you suspect may have a macular hole in her right eye. She reports to you that during the test the slit beam of light appeared thinned but not broken in the vertical direction, and was broken in the horizontal direction. Based upon her observation, what is the MOST likely diagnosis? Lamellar macular hole Epiretinal membrane Macular cyst Pseudo macular hole Full thickness macular hole Your Answer Explanation Watzke-Allen test: at the slit lamp with a fundus lens, a narrow slit beam is projected over the center of the suspected macular hole both vertically and horizontally. \- A patient with a full thickness macular hole will most often note that the beam of light appears thinned or broken \- A patient with a lamellar hole, pseudo-hole, or cyst will often report that the beam appears bent or distorted, but has uniform thickness Which of the following systemic diseases is MOST commonly associated with the presence of angioid streaks observed in the retina? Sickle cell disease Pseudoxanthoma elasticum Your Answer Marfan syndrome Paget\'s disease Ehlers-Danlos syndrome Explanation Approximately 50% of patients who present with angioid streaks have an associated systemic disease; the other 50% of cases are considered idiopathic. Pseudoxanthoma elasticum (PXE) is by far the most commonly associated systemic disease in these patients. In general, PXE is a rather uncommon, inherited, generalized connective tissue disorder whereby tissues in the body containing elastin are significantly affected. Up to 85% of patients with PXE will develop ocular complications, usually after the second decade of life. The combination of PXE and ocular involvement with angioid streaks is referred to as \"Gronblad-Strandberg syndrome.\" Patients with PXE typically have characteristic signs of very loose skin folds and yellow skin papules that are commonly observed in the neck region, axillae, and on flexor aspects of joints. These patients also frequently suffer from cardiovascular disease caused by accelerated atherosclerosis, and have an increased risk of developing gastrointestinal bleeds, which can be life-threatening. Ehlers-Danlos syndrome is another systemic condition that is occasionally associated with the presence of angioid streaks. It is a rare, usually dominantly inherited disorder of collagen in the body that is caused by a deficiency of hydroxylysine. Systemic features include thin, hyperelastic skin, hyperextensible joints, cardiovascular disease, and other systemic lesions. Besides angioid streaks, patients with Ehlers-Danlos syndrome can also develop other ocular conditions such as lens subluxation, blue sclera, high myopia, keratoconus and retinal detachments. Angioid streaks also occur in about 2-10% of patients diagnosed with Paget\'s disease. Paget\'s disease is a chronic, progressive (inherited in some cases) disease that is characterized by an enlarged skull, bone pain, frequent bone fractures, hearing loss, and cardiovascular complications. The disease may be localized to a few bones or may be generalized. In some cases, patients are even asymptomatic; however, in late stages, significant vision loss can ensue due to optic nerve compression from enlarging bone. Lab testing in these patients will show increased serum alkaline phosphatase and urine calcium levels. Less common systemic disorders that may cause the formation of angioid streaks include sickle-cell disease, acromegaly, senile elastosis, lead poisoning, and Marfan syndrome. Your 49-year-old patient reports that she recently started taking oral tamoxifen. In addition to an annual comprehensive eye examination with dilation, which of the following tests should be performed at each visit? Optic nerve optical coherence tomography (OCT) Macular optical coherence tomography (OCT) Your Answer Gonioscopy 10-2 threshold visual field Corneal topography 24-2 threshold visual field Explanation Tamoxifen is frequently used in the treatment of breast cancer. Patients taking this medication may experience decreased visual acuity due to the accumulation of white crystalline retinal deposits that are confined to the plexiform and nerve fiber layers; these are most densely concentrated around the paramacular region. OCT imaging of the macula can help detect subtle maculopathy associated with the use of tamoxifen. At lower dosages, tamoxifen can also cause pseudo-cystic cavities in the macula. Studies have shown that full-thickness macular holes were 5x more likely to be observed in patients taking tamoxifen, possibly caused by these foveal cavities. Ocular toxicity is typically associated with high doses in excess of 120 mg daily; it is not common with the standard daily dose of 20 mg. All patients on tamoxifen should have a baseline and yearly dilated eye examination with SD-OCT of the macula. Answer Correct In addition to retinal findings of bone-spicule pigmentation and retinal arteriolar attenuation, patients diagnosed with retinitis pigmentosa MOST commonly develop which of the following optic nerve changes? Optic disc hemorrhage Optic disc edema Optic disc cupping Optic disc pallor Your Answer Explanation The classic clinical triad of retinitis pigmentosa (RP) includes arteriolar attenuation, retinal bone-spicule pigmentation, and waxy optic disc pallor. Other ocular associations of retinitis pigmentosa may occur at any time during the disease, some of which may be amenable to treatment. These additional signs include the development of posterior subcapsular cataracts, myopia, vitreous changes (such as posterior vitreous detachment), and uveitis. Additionally, keratoconus, optic disc drusen, and open-angle glaucoma may also be associated with RP. What is the MOST common complication of a posterior vitreous detachment? Retinal hemorrhage Retinal detachment Central scotoma The perception of a floater Your Answer Vitreous hemorrhage Explanation Syneresis and liquification of the vitreous are part of the normal aging process, but they also may cause a posterior vitreal detachment (PVD). Generally, PVDs occur without complication, except for the perception of an annoying floater by the patient which will often somewhat regress with time. Rarely, a PVD can cause a retinal tear which may lead to a retinal detachment, epiretinal membrane, and vitreal and retinal hemorrhages. Monitor the patient carefully to ensure that none of these complications develop, and be sure to educate patients regarding the signs and symptoms of a retinal detachment. 23-year-old male patient presents with complaints of ocular irritation, redness, and discharge of both eyes that began yesterday. Upon slit-lamp examination, you notice bumps on the lower palebral conjunctiva. Which 2 of the following characteristics can help differentiate between a papillary and follicular reaction? (Select 2) Papillae are commonly associated with viral conjunctivitis Blood vessels associated with papillae pass over the surface, as the central portion is avascular Papillae are commonly associated with bacterial conjunctivitis Your Answer Papillae contain a central fibrovascular core that arborizes upon reaching the conjunctival surface Your Answer Explanation Conjunctival follicles typically present as discrete, pale yellowish-white, round elevations that are most prominent in the conjunctival fornices. Blood vessels associated with these bumps sweep over the surface of the follicle from the base, as they do not contain a vascular core. Follicles are usually 0.5 to 2.0mm in diameter but vary depending on the severity and duration of the disease. The presence of a follicular response is common in viral and chlamydial conjunctivitis, Parinaud\'s oculoglandular syndrome, and is also observed in relation to hypersensitivity reactions to topical medications. Conjunctival papillae are only found where the conjunctiva is attached to the underlying deeper fibrous layer, such as the tarsal conjunctiva and limbal bulbar conjunctiva. Smaller micropapillae form a mosaic pattern that appear as polygonal, elevated, red dots that are less than 1mm in size. These bumps have a central fibrovascular core that arborizes as the vessel reaches the surface of the papillae. Papillary reactions can occur secondary to allergic and bacterial conjunctivitis, contact lens wear, chronic blepharitis, superior limbic keratoconjunctivitis, and floppy eyelid syndrome. 23-year-old male is seen at your office for a comprehensive eye exam. He states that he has been waiting since he was 15 years old to undergo refractive surgery. His subjective refraction is -16.00 -0.75 x 180 OD and -15.00 - 0.25 x 167 OS, which he reports has been stable for four years. Considering his refractive error, which type of surgery would you suggest as the BEST option for him? Refractive lens exchange (RLE) Photo-refractive keratectomy (PRK) Conductive keratoplasty (CK) Implantable collamer lens (ICL) \| Your Answer Laser assisted in-situ keratomileusis (LASIK) Explanation Due to the nature of this patient\'s high prescription, the only viable options of the choices presented would be either ICLs (implantable collamer lenses) or RLE (refractive lens exchange). However, if this patient were to undergo a refractive lens exchange (in which the clear crystalline lens is removed and replaced with a corrective posterior chamber intraocular lens implant), he would end up presbyopic and would require some form of near correction. RLE procedures are best reserved for presbyopes who are dependent upon reading glasses already. Therefore, the best option for this patient would be implantable collamer lenses. This procedure offers several advantages in that it is not permanent and there is no thinning of the corneal tissue. With this surgery, a corrective lens is typically implanted behind the iris and in front of the lens without removal of the natural crystalline lens. However, one must exercise caution; if the surgeon is not careful, and either the corneal endothelium or the natural lens is touched during the procedure, there is a risk of endothelial cell loss or cataract formation. For lenses placed in the anterior chamber, a peripheral laser iridotomy is usually performed prior to lens implantation to prevent the development of pupillary block glaucoma. Conductive keratoplasty is a type of refractive surgery that is performed on low hyperopes (+0.75 to +3.00 D with less than 0.75 D of astigmatism). A thin probe is inserted into the peripheral cornea at specified intervals which delivers radiofrequency energy and causes shrinking of the surrounding collagen. The circular ring of altered collagen results in a steepening of the central cornea, and thus decreases the amount of hyperopia. The results of CK are often temporary and generally do not last more than a few years. Photo-refractive keratectomy (PRK) requires the use of a solution to remove the cornea epithelium, followed by an excimer laser to reshape the underlying tissue. PRK is often used in patients with thin corneas and can eliminate up to roughly 7.00 D of myopia. This procedure typically results in a more painful and longer recovery time than LASIK due to the need for the epithelium to regenerate and smooth out. PRK also requires the use of a bandage contact lens as the epithelium heals. LASIK also utilizes a laser to alter the corneal thickness and reshape the curvature of the cornea. Previous LASIK procedures utilized a microkeratome to cut a flap and expose the underlying tissue for sculpting. It is now more common for the flap to be created by a laser, which allows for better precision and reproducibility of the incision depth. Reportedly, LASIK can be used to correct up to 12.00 D of myopia, 6.00 D of astigmatism, and 6.00 D of hyperopia. LASIK is quite popular due to its favorable results, increased reliability, quick recovery time, and decreased level of discomfort. Which of the following statements is TRUE in regards to gonococcal keratoconjunctivitis? Neisseria gonorrhoeae is a Gram-positive organism Neisseria gonorrhoeae is incapable of invading an intact corneal epithelium Gonococcal infections do not result in pseudomembrane formation Lymphadenopathy in gonococcal infections is typically prominent Your Answer Explanation Gonorrheal infections typically have the following characteristics: \- Profuse conjunctival purulent discharge \- Eyelid tenderness and edema \- Severe conjunctival chemosis and hyperemia \- Pseudomembrane formation can occur \- Lymphadenopathy is typically prominent \- N. gonorrhoeae can invade an intact epithelium; therefore peripheral corneal ulceration can occur if conjunctivitis is not treated properly \- In severe cases, the ulceration can extend centrally, and eventual corneal perforation and endophthalmitis is possible \- Gram staining will reveal a Gram-negative organism with a kidney-shaped diplococcic appearance In adults, which organism is the most common cause of bacterial conjunctivitis in warmer climates? Neisseria meningiditis Staphylococcus aureus Streptococcus pneumonia Haemophilus influenza Your Answer Explanation Haemophilus influenza is the predominant cause of bacterial conjunctivitis in adults in warmer climates, while Streptococcus pneumonia is the most common cause in adults in cooler climates. Acute conjunctivitis is characterized by mucopurulent discharge that is worse in the morning. It usually begins unilaterally and spreads to the other eye. Under normal circumstances, the most common isolate in adults is S. aureus. In children under five years old, the common culprit of acute conjunctivitis is H. influenza. Ref:Hoang-Xuan, T., Baudouin C., Creuzot-Garcher, C. Inflammatory Diseases of the Conjunctiva, 1998 pg 112. Arlt\'s lines and Herbert\'s pits are associated with which of the following ocular conditions? Epidemic keratoconjunctivitis (EKC) Vernal limbic keratoconjunctivitis (VKC) Recurrent corneal erosion Trachoma Your Answer Explanation Trachoma (an infection caused by the organism Chlamydia trachomatis) is more common in lesser-developed countries and can cause blindness if not treated appropriately. Trachoma presents in several stages, initially starting with mucopurulent discharge, lymphadenopathy, red eye, small superior tarsal follicles, and mild superior pannus. This infection can eventually progress to horrible scarring of the eyelid and cornea, causing extremely poor visual acuity. Arlt\'s lines denote the characteristic linear scarring that occurs on the palpebral conjunctival surface. This scarring of the eyelids can cause entropion and trichiasis which can abrade the cornea and lead to corneal scarring and/or ulceration. Herbert\'s pits are conjunctival depressions or excavations caused by scarring of limbal follicles that occur along the limbocorneal junction. Treatments for trachoma include oral doxycycline, tetracycline, azithromycin, or erythromycin, along with topical tetracycline or erythromycin ointment. A recurrent corneal erosion generally occurs in response to a corneal abrasion incurred by something organic (like a finger-nail or a tree branch). The initial abrasion heals but a short time afterwards the patient experiences another episode without any new incidence of trauma. The second occurrence tends to transpire first thing in the morning; the eyelids stick to an unstable flap of tissue and rip it off like a band-aid when the eyes open. The best way to treat a recurrent corneal erosion is through the use of a topical antibiotic (unpreserved is best) to ensure sterility (as the cornea is exposed) as well as a bandage contact lens to speed up the healing process. Hyperosmotic drops or artificial tears should be prescribed for roughly 10-12 weeks to ensure healing and to allow for proper formation of hemidesmosomes to alleviate future episodes. Other treatments include stromal micropuncture or debridement in more severe cases. VKC is typically a condition of the young and presents with an increased frequency in males. This type of allergy often develops before age 14 and lasts for 4-10 years before the child outgrows it. It tends to occur predominantly in the spring and summer months. The condition usually progressively improves, with the first episode being the most severe. VKC is most often seen in patients who are prone to atopy and suffer from eczema, asthma or hay fever. Patients typically also suffer from itchy eyes and photophobia. The condition essentially presents as a very severe type of allergic conjunctivitis. Signs include cobblestone papillae of the upper lid, lid swelling, and ropy discharge that is worse in the morning. Corneal defects (usually superiorly) known as keratitis of Togby may also be present. Occasionally, patients will develop a shield ulcer and Tranta\'s dots, which are calcified eosinophils seen circumlimbally (they appear as chalky concretions) that often result in a foreign body sensation. Treatment includes mast cell stabilizers that should be started several weeks prior to re-occurring episodes, pulse steroid therapy, cool compresses, and sunglasses to help alleviate ensuing photophobia. Epidemic keratoconjunctivitis (EKC) is a very common and contagious infection of viral etiology. EKC is caused by the adenovirus; there are many different strains, but the two most common serotypes that cause ocular infections are types 8 and 19. EKC is said to follow the \"rule of 8s\" because type 8 is the serotype most frequently isolated. Additionally on the 8th day the patient typically presents with diffuse superficial punctate keratitis (SPK), followed 8 days later (16 days from inoculation) by the formation of sub-epithelial infiltrates (SEls). Once SEls are present, the patient is no longer considered contagious. Siens of EKC include follicular conjunctivitis, positive lymph adenopathy, and mild lid edema. Small sub-conjunctival hemorrhages, pseudo-membranes, and iritis may also be present. Treatment for this condition is generally palliative and consists of ocular lubrication, topical vasoconstrictors, cool or warm compresses, topical NSAIDs, and sunglasses. Some clinicians use a Betadine® (5%) off-label treatment in office, which seems to be rather effective if used in the early days. The use of steroids is still controversial because EKC and Herpes simplex virus (HSV) can initially present similarly, and steroid use on HSV can lead to corneal damage. Topical steroids are very effective if the patient suffers from SEls that are visually debilitating, but be sure to taper the steroid use in these patients. Inflammation solely of the corneal stroma (without the involvement of the epithelium or endothelium) is known as which of the following conditions? Interstitial keratitis Your Answer Corneal hydrops Bullous keratopathy Infiltrative keratitis Neurotrophic keratitis Explanation Interstitial keratitis (IK) is a condition in which inflammation is present in the corneal stroma in the absence of primary involvement of the corneal epithelium or endothelium. It is most often associated with congenital syphilis but may occur with other conditions such as tuberculosis, leprosy, Lyme disease, and other viral infections. Ligneous conjunctivitis is related to a deficiency of which of the following proteins? Plasminogen Your Answer Fibrinogen Myofibroblasts Fibronectin Actin Proteoglycans Explanation Ligneous conjunctivitis is a rare form of chronic, recurring conjunctivitis that is characterized by the presence of pseudomembranes on the palpebral conjunctivae. It may be inherited in an autosomal recessive pattern and is associated with type 1 plasminogen deficiency (hypoplasminogenemia), which often leads to impaired wound healing. Which of the following is TRUE regarding patients with a history of recurrent corneal erosions who wish to undergo refractive surgery? The patient should have laser assisted in situ keratomileusis (LASIK) A history of recurrent corneal erosions is an absolute contraindication and the patient should not undergo any type of corneal refractive surgery The patient should have a femtosecond flap vs. microkeratome flap The patient should have photorefractive keratectomy (PRK) Your Answer Explanation Recurrent corneal erosions occur in an area where the corneal epithelium is not tightly secured to the anterior stroma, usually from either a previous abrasion or epithelial basement membrane dystrophy. The mechanical action of creating a corneal flap with either a microkeratome or femtosecond laser can cause the epithelium to erode in the \"weakly adherent\" area. Therefore, it is not advisable to use either of those methods to treat the refractive error. Phototherapeutic keratectomy (PTK) has been shown to be an effective treatment for recurrent erosions. In this procedure, the corneal epithelium is debrided, and an excimer laser is used to ablate a very small amount of tissue. The newly ablated, smooth surface then acts to support proper re-epitheialization. PRK (Photorefractive keratectomy) is similar to PTK, except that the ablation is greater and corrects for the patient\'s refractive error; therefore, this procedure is best for patients with history of recurrent corneal erosions who wish to undergo refractive surgery. Which of the following corneal conditions occurs as a result of excessive amyloid deposition? Lattice dystrophy Your Answer Granular dystrophy Macular dystrophy Fleck dystrophy Explanation Lattice dystrophy is an autosomal dominant dystrophy (except for type Ill, which is autosomal recessive) with four sub-types that are categorized according to age of onset, systemic involvement, causative mutation, and appearance. Essentially, this condition is due to a deposition of amyloid that often causes a decrease in visual acuity. The pacifications in this dystrophy appear as lines (thick and/or thin) and dots (depending on the sub-type). Granular dystrophy results from a deposition of eosinophilic hyaline in the anterior stroma. Again, this condition is autosomal dominant and typically onsets in the first decade of life. As time passes, the deposits tend to coalesce and cause a decrease in visual acuity. Granular dystrophy presents with a clear limbal zone, and the stroma between the opacities also remains clear in the early stages of the condition. Macular dystrophy occurs secondary to a deposition of glycosaminoglycans (mucopolysaccharides) in the stroma during the first decade of life. This condition is autosomal recessive and usually causes poor vision by the time the patient reaches roughly 20-30 years of age due to corneal thinning and enlargement of opacities that involves all of the corneal layers. This dystrophy not only involves the central cornea, but extends all the way to the limbus. The preferred surgical intervention in these cases is a corneal transplant. Macular dystrophy is the most visually devastating of the three stromal dystrophies mentioned here. A good mnemonic for committing this to memory is: Marilyn Monroe Got Hers in Los Angeles (Macular-Mucopolysaccharide, Granular-Hyaline, Lattice-Amyloid). Fleck dystrophy is an autosomal dominant condition that has an onset in the first decade of life and occurs due to fleck or comma-like deposition of glycosaminoglycan in the stroma. This dystrophy rarely requires any intervention. What is the name of the corneal surgical procedure in which the corneal epithelium and partial thickness of the stroma are transplanted, leaving the deep stroma and endothelium intact? Deep lamellar keratoplasty Descemet\'s stripping endothelial keratoplasty Lamellar keratoplasty Your Answer Penetrating keratoplasty Explanation Lamellar keratoplasty involves a partial thickness excision and transplantation of the corneal epithelium and stroma only, leaving the deep stroma and corneal endothelium intact. This type of procedure is typically indicated in patients with localized corneal thinning, marginal corneal thinning or infiltration, or pacification of the superficial 1/3 of the corneal stroma. A deep anterior lamellar keratoplasty is a transplantation procedure in which all of the opaque corneal tissue is removed, almost all the way to the level of Descemet\'s membrane. It is indicated in patients who have a corneal disease involving 95% of the corneal thickness, but who maintain a healthy corneal endothelium with an absence of breaks in Descemet\'s membrane. A penetrating keratoplasty is a surgical procedure in which the full thickness of the cornea is replaced by donor tissue. This procedure is used in cases where the endothelium is compromised, there is dense and deep corneal scarring, severely infected corneal tissue, or in patients with degenerative diseases that could potentially recur. Which 2 of the following statements are TRUE in regards to the presence of Vogt\'s striae in patients with keratoconus? (Select 2) Vogt\'s striae are fine, vertical lines found deep within the corneal stroma and Descemet\'s membrane Your Answer Vogt\'s striae are most commonly found surrounding the base of the cone Vogt\'s striae will often disappear when external pressure is applied to the globe Your Answer Vogt\'s striae represent vertical folds in Bowman\'s membrane Vogt\'s striae are only observed in cases of keratoconus Explanation Vogt\'s striae are thin, fine, parallel, vertical lines that are commonly observed in patients with keratoconus. They are typically found radiating through the center of the cone, and represent stressed collagen lamellae deep within the deep corneal stroma and Descemet\'s membrane. These striae will usually disappear when external pressure is applied to the globe. Vogt\'s striae can also be present in patients with pellucid marginal degeneration but are most commonly found in cases of keratoconus. You are performing manual keratometry on your post-LASIK patient and realize that his corneal curvature is so flat that it falls outside of the normal range of the keratometer. Which of the following trial lenses would extend the range in the proper direction, and what adjustment do you need to make to the reading to obtain the true value? Add a +1.00 lens; and subtract 9D from the drum reading Add a +1.00 lens; and add 9D from the drum reading Add a -1.00 lens; and subtract 6D from the drum reading Your Answer Add a +1.00; lens and subtract 6D from the drum reading Add a -1.00 lens; and subtract 9D from the drum reading Add a -1.00 lens; and add 6D to the drum reading Explanation When measuring the keratometry values utilizing a manual keratometer, there are certain circumstances in which the reading may be out of the range of the drum values. In these cases, one will need to add a trial lens to the keratometer in order to extend the ranges (lenses are added to the patient\'s side of the keratometer). Cases in which the curvature is steeper than the drum reading allows, plus trial lenses are required, and when the reading is flatter than the drum reading allows, minus trial lenses are necessary. In the case of steeper curvatures, typically a +1.25 trial lens is tried first. If a measurement can be found with this lens, one will need to add about 8-9D to the drum reading in order to obtain the true value. A +1.25 lens will extend the range from about 52D to 60 or 61D. If keratometry values are even steeper (in the 60-68D range), a +2.25 trial lens can be utilized to extend the drum range even more. In these cases, about 16D is added to the drum reading to reach the true keratometry value. If the curvature is flatter than can be measured with the manual keratometer, a minus lens can be added to extend the range in the opposite direction. Typically a -1.00 trial lens will encompass keratometry readings from about 32-38D. If a -1.00 lens is added, one will need to subtract 6D from the drum reading. This is the case for the above patient. Which of the following statements is FALSE regarding pellucid marginal degeneration (PMD)? Differential diagnoses of PMD include Terrien\'s marginal degeneration and Mooren\'s ulcer High amounts of irregular or against-the-rule astigmatism typically appear in patients with PMD Acute hydrops can occur in PMD,1q leading to corneal scarring and neovascularization The corneal protrusion is in the same area as the corneal thinning in PMD Your Answer PMD is characterized by a narrow band of inferior corneal thinning that is approximately 1-2 mm in width Explanation Unlike keratoconus, the area of corneal protrusion in patients with PMD is superior to the area of corneal thinning (in keratoconus, the area of thinning and protrusion correspond). All of the other statements presented are true in regards to PMD. Two of the hallmark diagnostic signs of pellucid are the kissing doves pattern exhibited on corneal topography, and the extreme inferior positioning of a GP lens when placed on the eye. Which 3 of the following conditions may warrant the use of a bandage contact lens? (Select 3) Limbal girdle of Vogt Recurrent corneal erosion Your Answer Post photorefractive keratectomy surgery Herpes simplex keratitis Corneal ulcer Your Answer Arcus senilis Corneal abrasion Your Answer Explanation Bandage contact lenses can be used in situations where the corneal surface requires protection from mechanical irritation (such as trichiasis or entropion) or from eyelid movement over a corneal epithelial defect. A bandage contact lens can also be used to promote healing and pain relief (i.e. from a corneal abrasion, recurrent corneal erosion, or post-PRK surgery). In general, it is best to choose a silicone hydrogel soft contact lens that is approved for extended wear purposes that fits a little more steeply in order to reduce excess lens movement and mechanical friction. As a result of certain ocular diseases and surgical procedures, the sensitivity of the cornea to noxious stimuli may decrease. Which of the following terms describes this occurrence? Hypoesthesia Your Answer Hypoxia Hypercapnia Hyperalgesia Explanation Corneal sensation has been shown to variably decrease with the presence of certain ocular diseases such as herpes simplex, keratoconus, diabetes, and other corneal dystrophies. Additionally, following surgical procedures (mostly involving the anterior segment of the eye) such as photorefractive keratectomy (PRK) or laser-assisted in-situ keratomileusis (LASIK), desensitization of the cornea is common due to the disruption of corneal nerves during the procedure. This decrease in corneal sensitivity (regardless of the etiology) is known as hypoesthesia. Following surgical injury, it is thought that it may take 3-12 months (or longer) for corneal innervation and sensitization to maximally recover, as nerve regeneration typically occurs at a rate of approximately 1mm per month. Hyperalgesia is an increase in sensitivity to pain. Hypoxia is a condition of tissues of the body in which a region is deprived of an adequate supply of oxygen. Lastly, hypercapia is the condition of abnormally high levels of carbon dioxide in the blood. In which of the following refractive surgery procedures is the corneal epithelium completely removed prior to ablation? Radial keratotomy (RK) Laser-assisted in-situ keratomileusis (LASIK) Photorefractive keratectomy (PRK) Your Answer Laser-assisted epithelial keratomileusis (LASEK) Conductive keratoplasty (CK) Explanation Laser-assisted in-situ keratomileusis (LASIK), laser-assisted epithelial keratomileusis (LASEK), and photorefractive keratotomy (PRK) are all refractive surgery procedures that use an excimer laser to ablate corneal tissue, subsequently leading to correction of the refractive error. These techniques differ in the way in which the deeper corneal tissue (stroma) is reached. LASIK involves the creation of a flap of corneal tissue. LASEK involves the removal of the corneal epithelium in a sheet that is then repositioned after ablation is complete. In PRK, the epithelium is completely removed and a bandage contact lens placed over the cornea after ablation to allow the epithelium to heal. The excimer laser used in these refractive procedures is meant to alter corneal stromal tissue, thus the need to expose this layer of the cornea. Conductive keratoplasty is a procedure in which laser burns are placed in the corneal mid-periphery to induce stromal shrinkage and subsequent steepening of the cornea. Radial keratotomy involves the creation of radial incisions formed by a blade to flatten the corneal curvature. Which of the following layers of the cornea is MOST susceptible to thinning in patients with keratoconus? All layers of the cornea are equally susceptible to thinning Endothelium Epithelium V Stroma Your Answer Bowman\'s membrane Descemet\'s membrane Explanation Histological studies conducted on individuals diagnosed with keratoconus show that the layer of the cornea that experiences significant central or paracentral thinning is the corneal stromal layer. Other layers of the cornea also undergo changes resulting in characteristic clinical observations such as Vogt\'s striae (thin striations found deep in the stroma in the area of ectasia). Additionally, brown pigment deposition of iron in the epithelial layer can sometimes be seen at the base of the ectasia during the course of the disease. The appearance of prominent corneal nerves, endothelial guttata, and posterior shagreen are also common observations viewed on slit-lamp examination. Furthermore, acute corneal hydrops is an associated condition that can occurs when breaks in Descemet\'s membrane occur. Hypoxic conditions cause the cornea to become cloudy and lose its transparency. Which layer of the cornea is the FIRST to become edematous during these conditions? Bowman\'s membrane Epithelium Stroma Your Answer Endothelium Explanation The corneal epithelium is the first to swell in these conditions due to the fact that epithelial cells are bathed by the tear film which supplies this layer with oxygen. During periods of hypoxia, mitochondrial function slows and the cornea switches to glycolysis for ATP production (this is termed the Pasteur Effect). Anaerobic metabolism will cause a build-up of lactic acid and hydrogen ions, which in turn changes the pH of the cornea causing osmotic swelling. Contact lens wear (especially when worn overnight) is the most common cause of hypoxia of the cornea. Your patient had LASIK surgery approximately two years ago and is reporting that her distance vision has deteriorated. You find that her prescription has regressed slightly by 1.25 D of myopia in both eyes. After discussion, she wishes to undergo an enhancement. What is the MOST common complication associated with a LASIK enhancement? Infection Epithelial ingrowth Your Answer Diffuse lamellar keratitis Flap dislocation Explanation The most common complication associated with an enhancement after previously undergoing LASIK surgery is epithelial ingrowth. Although this condition can occur after the first LASIK procedure due to poor flap adhesion, or from stray epithelial cells remaining under the flap, it is far more common with enhancements. Some surgeons are attempting to decrease the incidence of epithelial ingrowth by re-cutting a new flap or by performing photorefractive keratotomy (PRK) instead. In general, epithelial ingrowth does not typically cause a problem if it is isolated to a small area and if there is little elevation or change with time. If the ingrowth is significant and vision is compromised, treatment may require that the flap be lifted and the offending cells removed. Patients diagnosed with vernal keratoconjunctivitis have an increased incidence of which of the following corneal diseases? Superior limbic keratoconjunctivitis Terrien\'s marginal degeneration Keratoconus Your Answer Thygeson\'s superficial punctate keratitis Explanation Patients with vernal keratoconjunctivitis are more likely than the general population to develop keratoconus This is due to the association of atopic disease in both conditions. Additionally, patients with VKC and keratoconus tend to have a more severe form of keratoconus that is commonly complicated by corneal hydrops and a greater tendency for corneal neovascularization. Which organism represents the MOST common etiology of bacterial conjunctivitis in children? Neisseria gonorrhoeae Moraxella catarrhalis Haemophilus influenzae Your Answer Staphylococcus aureus Streptococcus pneumoniae Chlamydia trachomatis Explanation In children, the most common causes of acute bacterial conjunctivitis are Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis (with Haemophilus representing the most common etiology). Acute bacterial conjunctivitis in adults is primarily due to Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenza, with Staphylococcus aureus representing the most common etiology. Hyperacute conjunctivitis is primarily due to Neisseria gonorrhoeae, and chronic conjunctivitis is primarily caused by Chlamydia trachomatis. Which type of hypersensitivity reaction (Gell and Coombs classification) is responsible for allergic conjunctivitis? Type IV Hypersensitivity Type Il Hypersensitivity Type Ill Hypersensitivity Type I Hypersensitivity Your Answer Explanation According to the Gell and Coombs classification of hypersensitivity reactions, Type I reactions are IgE-mediated reactions that result in an immediate response occurring within minutes of exposure. This type of reaction is seen in allergic disease. Type Il reactions are antibody-dependent cytotoxic reactions that are mediated by IgM/IgG and complement. Type Ill reactions are due to immune complex formation. Immune complex diseases include systemic lupus erythematosus, Arthus reactions and serum sickness. Type IV hypersensitivity is delayed-type hypersensitivity and is the result of T-lymphocyte responses. Typically, symptoms will occur 24-48 hours after exposure. Prime examples include the PPD test for TB, and contact dermatitis. While performing keratometry on your patient, you notice that the reflected corneal mires appear elliptical with the long axis located vertically. Which of the following keratometry values is this patient MOST likely to possess? 48.62 \@045 / 40.00 \@135 47.75@ 098 / 41.00 \@008 49.00 \@180 / 43.75 \@090 Your Answer This is the expected result and the patient does not have astigmatism Explanation The patient\'s cornea is steeper horizontally and therefore minimizes the image in this meridian, creating an ellipse with its axis located vertically. Because the flatter meridian is vertical, this patient is most likely to exhibit against-the-rule astigmatism in which the flat meridian of the cornea is located at 90 degrees +/- 30 degrees. Gram stains are used to differentiate between gram-positive and gram-negative bacteria. Why do gram-positive bacteria stain purple with crystal violet? Gram-positive bacteria cell walls contain teichoic acids which bind to crystal violet The large periplasmic spaces in the cellular wall allow for greater absorption of crystal violet Due to the presence of high amounts of peptidoglycan contained within the cellular wall Your Answer Gram-positive bacterial cell walls contain lipopolysaccharides which bind to crystal violet Explanation Crystal violet binds to peptidoglycan. The greater the percentage of peptidoglycan contained within the cellular wall, the greater the intensity of staining. Gram-positive cell walls are comprised of a larger amount of peptidoglycan (50-90%) than gram-negative cell walls (roughly 10%). Which of the following systemic conditions is MOST commonly associated with the development of interstitial keratitis? Lyme disease Sarcoidosis Syphilis Your Answer Human immunodeficiency virus Chlamydia Herpes simplex Explanation The presence of interstitial keratitis (IK) is essentially synonymous w