Macular OCT PDF

​ Macular OCT ○​ Retinal Layers ​ ○​ Tested Eye identification ​ ○​ Common conditions identified with OCT ​ Used as a diagnostic device to aid in the detection and management of patients with: ​ Narrow angles...

​ Macular OCT ○​ Retinal Layers ​ ○​ Tested Eye identification ​ ○​ Common conditions identified with OCT ​ Used as a diagnostic device to aid in the detection and management of patients with: ​ Narrow angles ​ Corneal pathologies ​ Retinal disease ○​ Retinal detachment ○​ Vitreous detachment ​ Macular conditions ○​ Macular hole ○​ Macular pucker ○​ Macular edema ○​ Drusen, exudates, cotton wool spots ​ Optic nerve abnormalities ​ Vascular/systemic conditions ○​ Causes for falsely high/low results ​ When superior vascular trunk bifurcates earlier will create a split bundle with the RNFL following this bifurcation ​ Leading to the appearance of RNFL thinning ​ This is physiological and benign finding ​ Tilted discs may present with superior and inferior RNFL bundles that appear to be shifted temporally, giving an abnormal appearance ​ Macular/retinal edema will result w/ RNFL peripapillary thickening ​ In such cases, glaucoma analysis is not reliable ​ Myelinated peripapillary RNFL will produce thick RNFL ​ Correlate clinically ​ Peripapillary atrophy will result in poor signal and capture strength and may result in a RNFL w/ zero thickness ​ Non-glaucomatous condition can also produce RNFL thinning resulting in abnormal glaucomatous evaluations ​ High myopia, sectorial retinal damage, peripapillary atrophy, and optic disc drusens ​ Causes of thicker RNFL leading to false negative evaluations in the presence of glaucoma: ​ Retinal edema ​ Retinal cyst ​ Retinal traction ​ Epiretinal membrane ​ Myelinated RNFL ​ ONH pit and edema ​ Signal: ​ Signal strength is defined as the average intensity value of the signal pixels ○​ A decenter scan will produce an erroneous RNFL thickness ​ Hyperreflective Bands: ***** ​ 4 important hyperreflective structures essential for good visual acuity: ○​ RPE ○​ Interdigitation Zone (IZ) ○​ Ellipsoid Zone (EZ) or Inner segment/outer segment (IS/OS)  ​ Photoreceptor integrity band ○​ External Limiting Membrane (ELM) ​ ONH OCT ○​ Most common conditions identified with OCT ​ Glaucoma ​ Asymmetry of the ON ​ NRR thinning ​ RNFL analysis ​ ON head edema ○​ Interpretation of results and diagnosis ○​ Causes for falsely high/low results ​ Fundus Photography ○​ C/D ratio evaluations ○​ Diabetic retinopathy signs and presentation ○​ Optic nerve evaluations ○​ Retinal evaluations ​ Ultrasonography ○​ A-scan structures ​ Interpretation ​ Peak identification: the prominent peaks observed on an A-scan represent different ocular structures (cornea, lens, retina, choroid, vitreous) ​ Reflectivity analysis: variations in the reflectivity of different structures help evaluate their integrity ○​ Helps identify between normal and abnormal findings ​ Comparison to normative data: we can compare results w/ normative data, to aid in identifying abnormal values ​ Spikes: 1.​ Probe interface meets the cornea: the tallest spike 2.​ Anterior and posterior lens: two spikes separated by a short distance 3.​ Vitreous: flat line 4.​ Retina: spike which decreases in amplitude 5.​ Sclera: second spike which decreases in amplitude 6.​ Orbital tissue: several spikes which decrease in amplitude  ○​ B-scan most common conditions diagnosed ​ Produces a two-dimensional imaging of ocular structures ​ Useful tool when we are unable to evaluate internal structures due to complete or partial view obstructions ​ Dense cataracts ​ Vitreous hemes ​ Opaque corneas ​ Eyelid pathology (lid edema, tarsorrhaphy) ​ Corneal opacity (edema, scar) ​ Anterior chamber opacity (hyphema, hypopyon) ​ Miosis ​ Dense cataracts ​ Vitreous opacity (vit. heme, vitritis) ​ Evaluation of posterior segment disorders: ​ Ciliary body lesions (cysts) ​ Ocular tumors (melanoma) ​ Vitreous pathology (asteroid hyalosis, persistent hyperplastic primary vitreous) ​ Retinal detachments (serous, rhegmatogenous, exudative) ​ Differentiation of posterior vitreous detachment from retina or choroid detachment ​ Differentiation of optic disc edema from optic disc drusens ​ FAN/ICG ○​ FAN stages ​ Pre-Arterial Phase: choroidal circulation is filled (choroidal flush), no dye has reached the retinal arteries ​ Very fast phase ​ Arterial Phase: 1 second after the prearterial phase. It extends from the first appearance of dye in the arteries until the whole arterial circulation is filled ​ CRA becomes white due to the fluorescein, but the CRV is still black ​ Capillary Phase: complete filling of the arteries and capillaries ​ Retinal capillaries are visible, especially around the ONH and FAZ ​ Venous Phase: subdivided according to venous filling and arterial emptying ​ Venous early stage (aka arterio-venous) ○​ Arteries and capillaries are filled and there is lamellar flow in the veins ​ Retinal veins central lumen is dark and the walls have fluorescence ○​ ​ Venous mid-stage ○​ Veins nearly filled ○​ Complete vein filling occurs over the next 10 seconds with maximum vessel fluorescence occurring ~30 sec after injection ○​ Aka recirculation phase ○​ Occurs about 2-4 minutes after injection ​ The veins and arteries remain roughly equal in brightness ​ The intensity of the fluorescein is slowly diminishing  ○​ ​ Venous late-stage ○​ Veins completely filled and the arteries are beginning to empty ​ Veins have more concentration of dye than arterioles ​ Dye starts to be excreted by the kidneys ○​ ○​ Late phase demonstrates the gradual elimination of fluorescein from the retinal and choroidal vasculature ○​ Occurs 7-15 minutes after injection ○​ Late staining of the optic disc is a normal finding ○​ Any other areas of late hyperfluorescence suggest the presence of an abnormality ○​  ○​ Conditions identified with FAN ​ Useful to evaluate retinal and choroidal circulation, abnormal RPE changes, vascular disease and neoplastic disorders: ​ ARMD ​ Diabetic retinopathy ​ Macular edema ​ Macular pucker ​ Ocular melanoma ​ Retinal detachment ​ Retinitis pigmentosa ​ Retinal vein occlusions ​ Central serous chorioretinopathy ​ Cystoid macular edema ​ Subretinal neovascular membranes ○​ NO ICG will be on the test ​ AFA ○​ AFA molecule ​ Lipofuscin is stimulated by a low energy laser ​ A barrier filter is used to only allow the RPE lipofuscin response to pass ​ It can perform 30 scans and provide an average calculated result ​ Provides a single monochromatic image w/ high contrast ○​ Hypo/hyper lesions/presentations ​ Hypofluorescent signal: “Red Hot Eyes Don’t Heal” ​ RPE atrophy ​ Fresh hemorrhages ​ Exudative lesions ​ Areas of dense hyperpigmentation ​ Hard drusen ​ Hyperfluorescent signal: ​ Yellow lesions related to high concentration of lipofuscin in RPE ○​ Best’s and Stargardt’s Disease  ○​ ​ Stargardt’s Disease ○​ ​ Best’s Disease ​ Older hemorrhages ​ Soft drusens ​ Refraction ​ Slit Lamp ○​ Special illumination techniques used for specific uses ​ Parallelepiped ​ Illumination source at ~45° (30°-60°) ○​ Click-stop in position (0°) ○​ Magnification 6-10X ​ Vitreous evaluation using a parallelepiped ○​ Click stop in position (0°) ○​ Beam angle: 45°-60° - w/ dilation; w/o dilation - pupil will get in the way and need smaller angle ○​ Beam width: 1-2 mm ○​ Max beam height ○​ Illumination: medium to high ○​ Magnification: 10-16X  ​ After focusing the posterior lens capsule, move the joystick towards the patient and focus the beam behind the lens (vitreous) ○​ Ask the patient to move the eyes up and straight for movement of the anterior vitreous ​ Can see floaters, PVD, WBCs, hemorrhages, pigmentary cells (Comes from RPE; resulting from a tear/detachment; Schaffers sign = retinal tear 100%) can all accumulate in the vitreous ​ Optic section ​ Used to determine the depth or elevation of a defect in the cornea or conjunctiva ​ Useful for: ○​ Assessing the depth of foreign bodies, scars, and opacities ○​ Locating which layer has an opacity ○​ Identifying the anatomical location of cataracts within the crystalline lens ○​ Assess corneal and conjunctival thickness ○​ Determine the presence of corneal edema, conjunctival chemosis ○​ Estimate the anterior chamber depth: Van Herrick Estimation Method ​ Used for A/C angle grading ​ Every patient needs to have A/C depth assessed, especially if dilation is to be performed ○​ Rule out angle occlusion ​ This technique only allows for T and N angle evaluation, not S and I ​ Split Limbal Technique allows for an estimation of the superior and inferior angles ​ Focus the optic section on the limbal cornea junction, splitting the cornea and the limbus ​ The angular separation seen at the limbus corneal junction is an estimation of the anterior chamber angle depth in degrees  ​ ​ Procedure: ​ Optic section placed near the limbus ​ Angle: 60°-80° ​ Magnification: 16X ​ Beam height: shortened ​ Conical beam ​ Used to examine the A/C for cells (WBCs floating around) or flare (protein accumulation as a byproduct of inflammation) ○​ Very important in inflammation cases, pain ​ Must be performed before dilation and applanation tonometry ​ Procedure: ○​ Click stop in position (0°) ○​ Angle: ~60° ○​ Width: conic section or parallelepiped of 1x2 mm ○​ Illumination: max ○​ Room has to be completely dark and examiner must be dark adapted ○​ Magnification: 25-40X ​ Focus the conical beam between the cornea and the anterior lens surface, focus on the iris at the pupillary margin ○​ Pull back the slit lamp and focus in the anterior chamber so light is seen passing though the out of focus cornea and lens (forming a conical beam) ​ Observe the dark zone between the out of focus cornea and lens ○​ Zone is normally optically empty and appears totally black ​ The convection currents of the aqueous will move any protein or cells up and through this zone. ○​ Watch and count the number of cells seen during a minute period. ​ Retro-illumination  ​ Parallelepiped that bounces unfocused light off one structure while observing the back lighting of another ○​ Light beam is reflected off another structure ​ 2 types: direct and indirect ​ Specular reflection ​ (allows us to evaluate endothelium-corneal dystrophies such as Fuchs) ○​ Best way to evaluate the endothelial cells of the cornea OR the epithelial cells on the lens ○​ Procedure: ​ Parallelepiped ​ Angle: 60°-90° ​ Magnification: 25-40X ​ Illumination: high ​ Monocular view ○​ Place the microscope angle at 30°-45° and the illumination angle at 30°-45° from the midline ​ Has to be the same for both ○​ ○​ Obtain a sharply focused parallelepiped of the cornea ○​ Slowly advance it across the cornea until a dazzling reflection of the filaments is seen ​ Look for the light reflex, it is only seen by one eye ​ There will be a point where two images of the filament are seen, one bright and the other ghostlike (cooper-yellow in color) ​ Important for pre- and post-ops ○​ Focus the biomicroscope on the ghostlike image until a mosaic of hexagonal cells is seen (orange peel appearance) ​ Use high magnification  ​ Sclerotic scatter ​ Parallelepiped at the limbus to scatter light internally throughout the cornea ​ In the case of Central Corneal Clouding (CCC), it is observed with the naked eye, the angle of oculars is directly opposite from the light source. ○​ If positive CCC, when observed haziness will be seen ​ Procedure: ○​ Magnification 6-10X (if using the oculars) ○​ Click stop in position (0°) ○​ Angle of 45-90° ○​ Width 1-2mm ○​ Height max ○​ Medium illumination ○​ Dark room ​ Tangential illumination and oscillation ​ Slit-beam is given an oscillatory movement by which it is often possible to see minute objects or filaments especially in the aqueous which would otherwise escape detection ​ Procedure: ○​ Angle at 70°-90° to the oculars ○​ Moderate slit width ○​ Begin w/ low magnification ○​ High illumination ​ To observe elevations in the iris: cysts, tumors ○​ Cataract gradings and evaluations ​ Cortical cataract ​ Grade 1: Up to 30%; VA: 20/20 ​ Grade 2: 30-60%; VA: 20/20 - 20/25 ​ Grade 3: 60-80%; VA: 20/30 - 20/40 ​ Grade 4: Whole cortex opacified; VA: 20/30, 20/40, 20/60 ​ Nuclear cataract ​ Grade 1: Light yellow; VA: 20/20 ​ Grade 2: Yellow; VA: 20/20 ​ Grade 3: Orange; VA: 20/25 ​ Grade 4: Brown; VA: 20/30 - 20/40 ​ Subcapsular cataract ​ Grade 1: 5-10%; VA: 20/30 ​ Grade 2: Up to 30%; VA: 20/40 ​ Grade 3: Up to 50%; VA: 20/40 to 20/60  ​ Grade 4: Above 50%; VA: 20/70 - 20/100, sometimes worse ​ Gonioscopy ○​ Gonioscopy results evaluation ​ Draw a large X and record the most posterior angle structure observed in each quadrant and record the pigmentation of the trabecular meshwork in each quadrant (scale from 0 to 4+) ​ Iris configuration: ​ Should document the iris as convex (steep), regular (flat), or concave ​ Plateau iris: in SLE, the center might appear as an open A/C but with the gonio lens, the iris drapes over the CB producing the characteristic sine wave or double hump ○​ This is a form of PCAG ​ Peripheral anterior synechia (PAS): adhesion of the iris to the TM ​ Seen in primary angle closure glaucoma, chronic anterior uveitis, iridocorneal endothelial syndrome (ICE) ​ ​ Neovascularization: seen in NVG, Fuch’s heterochromic cyclitis, chronic uveitis, Sturge Weber Syndrome, posterior pole vascular conditions (DM, CVO, OIS, Radiation) ​ ​ Fuch’s heterochromic cyclitis: ○​ Asymmetry in iris color, typically w/ mild iritis in the eye w/ the lighter colored-iris  ○​ Patients can have fine vessels crossing to the TM that are susceptible to rupture w/ trauma and produce hyphema ○​ ○​ ○​ Most common conditions ​ Pigment in Schwalbe’s Line: termed Sampolesi’s line ​ Pigmentary dispersion syndrome - Pigmentary glaucoma ​ Pseudoexflative syndrome - Pseudoexfoliative glaucoma ​ Abnormal findings ​ ○​ Gonioscopy indications ​ Any patient w/ VH grades less than 2 ​ Glaucoma: open and closed. Primary and secondary. ​ Glaucoma syndromes or suspects ​ Predisposition to NVI and NVA ​ History of eye trauma* ​ Iris lesions ​ Angle neoplasia ​ Synechia ​ Uveitis ​ *Contraindicated in the presence of corneal penetrating injuries or hyphema ○​ Trauma indications  ​ May cause: ​ Angle recession: tear between the longitudinal and circular muscle fibers of the CB ​ Iridodialysis: tear in the root of the iris and the iris is no longer attached to the angle ​ Trabecular dialysis: tear of the anterior TM creating a flap hinged in the SS ​ Cyclodialysis: separation of the CB from SS ​ Blood in Schlemm’s canal: ​ Seen in: Cavernous carotid fistula (CCF), Sturge-Weber Syndrome, Superior vena cava obstruction ​ It may present as a normal reflux into Schlemm’s canal and may be seen during routine gonioscopy ​ More commonly blood in the canal is seen under conditions of elevated episcleral venous pressure ○​ This should always be correlated w/ dilated episcleral vessels ​ Hypotony may also cause blood to reflux into the canal ​ Foreign Body ○​ Findings, testing recommended, management ○​ Organic FB: ​ Animal or plant origin ​ Higher rate of fungal infection ○​ Inorganic FB: ​ Non-metallic ​ Objects not composed of a living organism ○​ Sand, plastic, stone, glass ​ Typically causes a less inflammatory reaction ​ Metallic ​ An object composed of metal ​ May lead to the creation of rust rings ○​ Common symptoms: tearing, pain, light sensitivity, decreased vision, hyperemia, FBS ○​ Indications of a penetrating IoFB ​ (+) Seidel sign ​ Shallow anterior chamber ​ Hyphema ​ Iris/pupil irregularities ​ Break in Descemet’s membrane  ​ Traumatic cataract ​ Peaked iris or pupillary defect ○​ Suspected IOFB ​ DFE to evaluate retina/periphery ​ Plain x-rays ​ B-scans ​ Ultrasound biomicroscopy (UBM) ​ Anterior segment OCT ​ Orbital CT scan ​ If metal IOFB, tetanus shot is necessary ○​ Post-removal of superficial conjunctival FB ​ After the removal, an abrasion will be left so ​ Rx ophthalmic ab soln. or ung for prophylaxis ​ Polytrim ophth. soln. 1 gtt q 6 hr in affected eye ​ Polysporin ung q 6-12 hr ​ Cycloplegia or BSCL are rarely needed ​ F/U as needed (5-7 d); conjunctiva heals w/in 12-24 hrs ○​ Secondary infections are possible, more common in embedded FB ○​ Superficial Punctate Keratitis ​ Could result after irrigation due to mechanical disruption of the cornea ○​ Reassure the patient about possible subconjunctival hemes secondary to FB removal ○​ FB in bulbar conjunctiva may cause a perforating injury, especially if caused by a high-speed projectile (hammering, grinding metal) ○​ Post corneal FB removal ​ Broad-spectrum antibiotics for 7 days ​ BSCLs reduces discomfort, protects the epithelium, promotes healing and decreases risk of corneal erosion ​ In a non-CL wearer it may cause discomfort or may become dislodge ​ May contribute to a more infective climate ​ Monitor closely ​ Remove CL in 24 hrs and evaluate for edema and striae ​ Pressure patch can help with pain, but will leave the patient with no binocular vision ​ Usually not needed, but some benefit from them ​ F/U in 24 hours  ​ Non-central superficial corneal FB usually just need topical antibiotic ​ If inflammation or the amount of burring was extensive: ​ Homatropine BID/3 days, Topical antibiotic ​ Steroids are contraindicated until re-epithelization occurs ​ Even in uveitis/iritis presentation ​ After re-epithelization if needed can be started ​ Keep in mind steroids decrease healing and can lead to a superinfection ​ Amniotic membrane for central, deep corneal FB, where there are greater scaring risks ​ For large abrasions Muro128 (NaCl 0.05%) is recommended ​ Tonometry ○​ Imbert-Fick law ​ States that “the pressure in a sphere filled w/ fluid and surrounded by an infinitely thin and flexible membrane is measure by the counter-pressure which just flattens the membrane to a plane.” ​ Pressure inside an ideal sphere (P) is equal to the force (F) necessary to flatten the sphere’s surface, divided by the area (A) that was flattened. ​ 𝑃 =F/A −−−→ 𝐹 = 𝑃𝐴 ​ Pressure (P) can be determined if the force (F) is fixed or if the area (A) is fixed ​ Cornea is not a perfect sphere and it is not infinitely thin and perfectly elastic ​ Variable to the Imbert-Fick Law ○​ Indications ​ The measurement of the tension of the eye ​ Uses: all routine examinations, glaucoma diagnosis and management, trauma, uveitis, medication SE ○​ CCT (3.06 mm) - overapplanation vs underapplanation  ○​ ​ Lacrimal ○​ Jones Test ​ Jones I: used to test the patency of the excretory system (which is responsible for tear drainage) ​ Instill fluorescein to lower cul de sac ​ After 5 min, ask the patient to occlude the nostril ipsilateral to the non-tested eye, & blow the nostril of the tested eye ​ Inspect the tissue for fluorescein presence using a Burston lamp or cobalt blue filter ​ Positive Jones I: presence of fluorescein in the tissue ○​ Lacrimal system is patent and functioning ​ Negative Jones I: no presence of fluorescein in the tissue ○​ Wait 5 min and repeat the test ○​ If still no evidence of fluorescein, place a sterile cotton tip applicator 1 cm into the nose, under the inferior meatus for 10 sec ○​ Remove the applicator and examine the fluorescein ○​ If fluorescein is seen, then the system is patent and just enough to blow out ​ If no fluorescein is seen on the cotton applicator, gently massage the lacrimal sac and ask the patient to blow their nose again ○​ If fluorescein is seen: this is a positive Jones 1 test w/ narrowing or partial nasolacrimal duct obstruction  ○​ If no fluorescein is seen: this is a negative Jones 1 test, indicating an obstructed excretory system ○​ Perform the Jones 2 test ​ Jones II: performed after Jones I is negative ​ Irrigate w/ saline soln. in the inferior canaliculus ​ Recover some saline soln. asking the patient to lean forward and expectorate into a basin, blow their nose into a tissue, or place a cotton tip applicator ​ Examine for the presence or absence of fluorescein ​ Positive Jones II: fluorescein is present in the tissue/basin and if the patient reports that they felt it and swallowed ○​ Also + if patient can feel saline in throat ​ Negative Jones II: no fluorescein was recovered or saline was not felt ○​ May need dacryocystography ​ Correlation w/ Jones I test: a negative Jones I and positive Jones II identifies a functionally blocked system, other narrow or partially blocked system but still patent ○​ Schirmer I & II ​ Schirmer I ​ Evaluate the integrity of the lacrimal secretion system and how many tears are being produced ​ Measures primarily aqueous production, due to the aqueous layer composing the largest part of the tear film ​ Total tear secretion is the sum of basal and reflex secretion ○​ No anesthesia is used ​ Schirmer I is performed using Whatman no.41 filter paper ​ Apply strip w/ the folded end onto the lower lid margin at the lateral canthus after during the excess tears ○​ Make sure the cornea is touched! ○​ Ask the patient to look nasally and insert temporally ​ Instruct the patient to keep their eyes open and blink normally ​ Evaluate the strip after 5 min and measure the amount of wetting on the filter ○​ Less than 10 mm is significant for decreased lacrimal secretion ○​ Less than 5 mm is diagnostic of lacrimal insufficiency  ○​ If over 25 mm, excessive reflex tearing, basal secretion test should be performed ​ Basal secretion test: ○​ This will allow for basal reflex measurement only, eliminating the reflex by irritation ○​ Apply anesthetic and measure basal secretion production ​ some lipid molecules are attracted by mucin layer -> mucin becomes hydrophobic and tear film ruptures ○​ Indicate of tear film instability in all different causes of dry eye ○​ W/ fluorescein (invasive)-- reflex tearing ○​ Non-invasive (toposcope) ○​ The more dry spots, the more the instability ○​ Do not perform after instilling anesthesia- false positives! ○​ Values of < 10 s are considered abnormal ​ 5-9 s are borderline dry eye  ​ < 5 s are clearly indicative of dry eye ○​ DES condition, factors, diagnosis, ect... ​ Defined as: “”A multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.” ​ Signs: ​ Bulbar conjunctival hyperemia ​ Redundant bulbar conjunctiva = conj. chalasis (conj. moves a lot) ​ Decreased tear meniscus ​ Irregular corneal surface ​ Increased tear film debris ​ Fine, granular, confluent or coarse epithelial keratopathy ​ Order of treatment: ​ Lubricant/artificial tears/ omega 3 ​ Restasis (Cyclosporin) ​ IPL (If MGD: to open MG) ​ Steroids (FML) ​ Influences: ​ Gender: females more than males ​ Age: postmenopausal women ​ Occupations and environmental factors ​ Cl wear ​ Systemic condition such as thyroid disorders (Thyroid eye disease -> proptosis -> lagothalmos -> dry eye) ​ Medications, such as antihistamines (Benadryl, Xyzal, Claritin, Allegra) ​ Blink rate, palpebral fissure widening, and video display terminal (VDT) use can also influence in DES ​ Presentation: ​ Pseudoepiphora due to aqueous deficiency ​ Contact lens wearer may remain symptomatic, but SCL wearers for over 10 years, typically develop DES ​ Medications such as anticholinergic, anxiolytics and antihistamines can decrease aqueous production ​ Blinks, eyelids and lashes in relation w/ DES ​ The eyelids neural, muscular, and structural components must remain intact in order to maintain a healthy tear film ​ Problems w/ the tear film may present from: ○​ Lagophthalmos ○​ Myokymia ○​ Tear hyperosmolarity w/ decreased tear volume during sleep ○​ Overnight cl wear ○​ Bell’s palsy ○​ Ectropion ○​ Inflammation or trauma to the eyelids ○​ Trichiasis ○​ Blepharitis ○​ Meibomian gland dysfunction (MGD)