Eye Anatomy Review Notes PDF

Eye anatomy Iris Pupil Sciera Retina Muscles--~. - -- acula Conjunctiva-.._I...

Eye anatomy Iris Pupil Sciera Retina Muscles--~. - -- acula Conjunctiva-.._I ~; ,, ,/ Optic Cornea- ~ I e Lens--~'~ \ L ) Vitreous-~~ ~ CamScanner What structures are at the front of the eye? The fr ont of the eye consists of the following tissues: conjunctiva, sclera, cornea, iris, ciliary body and crystalline fens. The main job ls to allow light to enter the eye and to focus this light onto the retina. T he conjunctiva is the thin layer that lines the front of the sclera and also the inner surfaces of the eyelids. It contains glands that secrete lubricating fluids as well as lymphoid tissue. The conjunctiva is important in keeping the eye moist and in protecting the eye from infection. Ory eye syndrome occurs when there are problems with the conjunctiva. The sclera is the tough outer wall of the eye. It is the white part of the eye. The sclera maintains the structure of the eye and provides support for all the other eye tissues. The eye movement muscles are attached to the sclera - anchor points on the sclera allow the eyeball to move when the eye movement muscles contract. The cornea is the clear, front window of the eye. It is transparent; this allows light to enter the eyeball. As light passes through the cornea, it becomes refracted. Together with the lens, the cornea is responsible for focusing light onto the retina. The space in between the cornea and lens is called the anterior chamber, which is filled by aqueous humor. The aqueous humor provides nutrients and oxygen to the cornea. The Iris is the colored part of the eye. It is the membrane that sits between the cornea and the lens. The iris color depends on the amount of pigment in the iris. Those with dark brown irides have a lot of iris pigment. The pupil is the round opening in the center of the iris. The iris is responsible for controlling the amount of light that enters the eye through the pupil. When there is too much light, the iris muscles constrict the pupil to reduce the amount of fight entering the eye. When it is dark, the iris muscles dilate the pupil to allow as much light to enter the eye as possible. The crystalline lens is located just behind the iris. It is held in place in the eye by zonules (also known as suspensory ligaments) that attach it to the ciliary body. Together with the cornea, it is responsible for focusing light onto the retina. Changing its thickness allows you to change focus from far to near and vice versa (i.e. accommodate). As you grow older, this ability to change the focusing distance diminishes and you end up needing to wear reading glasses· this is called presbyopia. Age also causes the lens to become progressively more cloudy, resulting in cataract formation. The cillary body is positioned just behind the iris. Its two main functions are to produce aqueous humor and to change the thickness of the lens by stretching or relaxing the zonules that are attached to it. And the structures at the back of the eye? The back compartment consists of the following: vitreous humor, retina, choroid and optic nerve.The main job is to allow light entering the eye to reach the retina, and to send the light signals to the brain for analysis. The vitreous humor is the jelly-like substance that fills the large back cavity between the lens and the retina. It is transparent and allows light to be focused onto the retina. The vitreous humor also helps the eye to maintain its shape and turgidity. Vitreous loss into the anterior chamber is one of the complications that can occur during cataract surgery. The retina is the light-sensitive innermost lining of the eyeball. It is probably easiest to think of the retina as wallpaper in a room. The retina consists of the retinal pigment epithelial layer and neurosensory retina. The retinal pigment epithelium helps to maintain and support the neurosensory retina. The neurosensory retina detects, absorbs and processes the light that enters the eye. Retinal photoreceptor cells in the neurosensory retina collect light signals and convert them to bio-electrical signals, which are then sent to the optic nerve. There are two types of photoreceptor cells: rods and cones. Rod photoreceptors are located in the peripheral retina, and are responsible for night vision and detection of motion. Cone photoreceptors are mostly concentrated at the macula (center of the retina) and are important for fine detailed visual acuity and color vision. Any damage to the macula, such as in macular degeneration, will cause blurring of the central vision. (Image adapted from the internet) The optic nerve is the cable connecting the eye to the brain. It is composed of well over one million nerve fibers. It transmits bio-electrical information from the neurosensory retina to the brain, so that the brain can interpret what it is that you are seeing. Your vision can be affected by damage to the optic nerve, such as in glaucoma and optic neuritis. The choroid is the layer between the retina (wallpaper) and sclera (wall). It is full of blood vessels and is responsible for supplying nutrients to the retina. The dark melanin pigment in the choroid absorbs any excess light in the eye. CamScanner  ; ~ ~ , J\ n nu R C\t -....... l· i -· f I l ' \ ,,,,~ i!)i fr=~F' n ~ -. ( : ,r.. - ,, ' '\ " ~ _; ,,,.,- ft ~' A i V 7 r. n I t Pr; R 'J\A FT RV l\. r.~ :I...J·~ Measures all areas of the eyesight, including the side, or peripheral vision. A perimetry test can help find certain patterns of vision loss. This may mean a certain type of eye disease is present. It is very useful in finding early changes in vision caused by nerve damage from glaucoma. Regular perimetry tests can be used to see if treatment for glaucoma is preventing further vision loss. To do the test, the patient must sit and look inside a bowl-shaped instrument called a perimeter. ,Vbii staring at the center of the bowl, lights flash. He will press a button each time you see a flash. A computer records the spot of each flash and if you pressed the button when the light flashed in that spot. At the end of the test, a printout shows if there are areas of vision where patient did not see the flashe! of light. These are areas of vision loss. Loss of peripheral vision is often an early sign of gJaucoma. , I. ~--- a oo L!1L±i1!.! T~- f ll9'Jllf' T.,. ~ L J.·M POliE-..: -NICI - ww -·..... tait,111111 "-"- V...J.... 6'> II). ,J :005 MIC d ifi' >j 4 I \ ff i M r ,. ,. "' " , ~....... ~ 'f..· -... - -.'. ~:;.:_f ~; =...,.., u.. ,, ,........,..,. ~ :~ : :: ~I: ;; ; : ,. ,... J...... ,.. ::::-::1:~::~.... ~I I ,I I I C t O..... ,! , ,.,..... ---........ , -4-4...... 10-.:,...-...........................................,. , ' --~..··· ····~..,..... ·· - '7 -.. '., '-"' :: , i'... ' !. d. CamScanner llf) T f r /\, j - - --~.,...-. -----... ~.......... ~.:..:·-.. f is a non-invasive imaging test. OCT uses light waves to take cross-section pictures of your retina. With OCT, we can see each of the retina's distinctive layers. This allows us to map and measure their thickness. These measurements help with diagnosis. They also provide treatment guidance for glaucoma and diseases of the retina. These retinal diseases include age-related macular degeneration (AMD) and diabetic eye disease. OCT is often used to evaluate disorders of the optic nerve as well. The OCT exam helps your eye doctor see changes to the fibers of the optic nerve. For example, it can detect changes caused by glaucoma. OCT relies on light waves. It cannot be used with conditions that interfere with light passing through the eye. These conditions include dense cataracts or significant bleeding in the vitreous. What Conditions Can OCT Help_to Diagnose? OCT is useful in diagnosing many eye conditions, including: Macular Hole Macular Pucker Macular Edema Age-Related Macular Degeneration Glaucoma Central Serous Retinopathy Diabetic Retinopathy Vitreo-Macular Traction (VMT) CamScanner  PHOTO involves capturing a photograph of the back of the eye, i.e. fund us or the retina, all the retina blood vessels, and the optic neIVe. The fundus eye test is frequently used to document the retina condition, and is also called the colour fundus photograph and forms an essential step in treating diseases of the retina. It is used to inspect anomalies that affect the eyes and blood vessels of the retina and monitor these diseases' progression. It is vital for disease processes such as macular degeneration, retinal neoplasms, choroid disturbances and diabetic eye disease, and associated macular oedema. Additionally, it aids in identifying glaucoma, multiple sclerosis, and other central nervous system abnormalities. DISC PHOTO Disc photography is a diagnostic imaging test used to detect problems in the optic nerve head (region where the optic nerve connects to the retina). CamScanner  T 1 F.._~. T -a simple, quick, and painless examination used to measure the thickness of the cornea. -Central corneal thickness (CCT) is an important parameter in refractive surgery, in the assessment of corneal disease, and for risk pro-filing in ocular hypertension and glaucoma -The cornea generally measures around 500 or 600 microns in the central area, and between 600 and 800 in the peripheral area. Corneal Topogr?11hv / Ocu!vze r useful for examining characteristics of the cornea such as shape, curvature, power and thickness. test provides detailed 3D maps of the cornea's shape and curvature and enables detection of corneal diseases, and irregular corneal conditions, such as swelling, scarring, abrasions, deformities, and irregular astigmatisms. plays an important role in laser in situ keratomileusis (LASIK). Preoperative screening permits the detection of keratoconus and other corneal shape anomalies that may be a contraindication for refractive surgery. cataract surgeons have come to appreciate that preoperative topography can help them to determine patients' candidacy for premium IOLs as well as to identify irregularities or ocular surface conditions that may affect their postoperative visual results. CamScanner is a diagnostic procedure that uses a special camera to record the blood flow in tht RE TIN A - the light-sensitive tissue at the back of the eye. What is FA used for? Macular Edema Diabetic Retinopathy Macular Degeneration Macular Pucker Ocular Melanoma also used to: Track changes in eye disease over time Target treatment areas CamScanner  NORMAL RETINA PROLIFERATIVE DIABETIC RETINOPATHV AGE-RELATFn MArl II 4R nFriFNFRATION CamScanner  RETINAL DETACHMENT RETINITIS PIGMENTOSA How is Fluorescein Angiography done? The nurse will put drops in patient's eves to dilate (widen) the pupils. A yellowish colored dye (fluorescein) is injected in a vein, usually in arm. It takes about 10-JS seconds for the dye to travel throughout the body. The dye eventually reaches the blood vessels in ti: eye, which causes them to '"fluoresce," or shine brightly. As the dye passes through your retina, a special camera takes pictures. These pictures helps the ophthalmologist see any problems or where to focus treatment. What to expect after Fluorescein Angiography? The effects of dilating eye drops can last several hours and cause blurry vision and light sensitivity. Be sure to Bring sunglasses Have someone drive the patient home afterwards CamScanner  I is performed during the pre-operative assessment for all patients undergoing cataract surgery. The measurements obtained are used to calculate the appropriate intraocular lens for each patient. Since its inception, the formula for calculating lens power has evolved, with numerous proposed formulas the process of measuring the power of the cornea (keratometry) and the length of the eye, and using this data to determine the ideal intraocular lens power. If this calculation is not performed, or if it is inaccurate, then patients may be left with a significant refractive error. IOLs Monofocal IOLs provide the clearest Near ✓✓✓ x Intermediate Distance A Multifocal lens implant is d esigned to correct your near. intermediate Astigmatism vision at one distance. and d istance vision. In the appropriate patient. th is can m ean less dependence on glasses.· Multifocal intraocular lenses, meanwhile, are used to simultaneously ~fl~[BuhU~,'.,I ~@ Near Intermediate Distance Astigmatism improve near vision~ intermediate vision, and distance vision. They utilize concentric rings of varying ~_./ XX ✓✓ thickness, to allow the eye to focus The m ajori t y of p atients have some level of a stigm atism. Modera te to severe levels of asti gm atism can now be corrected wi t h a special toric images from all distances onto the lens. Th is can reduce the d ependence on glasses for d istance vi sion." retina. =r,1: ) rev XX ✓ X Torie lens is specially shaped and ~ -f ir, Near Intermediate Dl1tance A1ti&matl5m helps patients see at a distance, as well as correct for astigmatism. Toric-multifocal IOLs correct your Our stond ard lens is suit.:ible for p.:iticn ts who do not m ind w e.-i ri ng astigmatism while allowing you to see glasses an d/or rea din g glasses. This lens h as a single focal po in t and ~lasses will be require d for o ther d ist ances. Th is lens 1s ty p ically clearly at all distances cove red by M edica re and insuran ce: ·cost ,n ,1 da, t,on ro Merl,c,1,~ ~ndror insllfance co-pJymenrs. aei!ur.llbles 311d co-,nsur,wce CamScanner Astigm1attis1u is usually caused by your cornea having an irregular shape. It' s a type of refractive error - an extremely common eye condition that causes blurred v1s1on. Usually, eyes are row1d, like a basebaJI. If you have astigmatism, your eye is shaped like a football or the back of a spoon. This makes light that enters your eyes bend unevenJy and affects your vision at all distances. No Regular Irregular Astigmatism Astigmatism Astigmatism ~ fNormal Eye ~ Astigmatic Eye M uitiple Focal points Astigmatic'\_ Cornea '--.___ cornea '\ I A Light ) I /. \ Light Lens - Lens - - ---............. ----Normal Vision -- ----------------------- Astigmatic Vision CamScanner  -Sc et utilizes an ultrasound device for diagnostic testing. This device can determine the length of the eye and can be useful in diagnosing common sight disorders. In A-Scan, a thin, parallel sound beam is emitted from the probe tip, with an echo bouncing back into the probe tip as the sound beam strikes each interface.. Contact. Immersion What is the immersion technique in A-scan? Immersion is preferred over applanation. With the immersion A-scan technique, the probe tip does not come into contact with the cornea. Instead, the ultrasound beam is coupled to the eye through fluid. Because there is no corneal compression, the displayed result more closely represents the true axial length. How is an A-scan performed? For A-scans, your eyes will be numbed with anesthetic drops. You will sit in a chair and place your chin on a chin rest and look straight ahead. The ·ultrasound wand will be placed on the front surface of the eye. CamScanner B scan, or Bright Scan ultrasonography is a diagnostic imaging tool utilized when the view to the back of the eye, or posterior segment is hjndered. The posterior segment of the eye is the back two- thirds of the eye and consists of the vitreous, retina, optic nerve, and choroid. lf the posterior segment of the eye is difficult for the ophthalmologist to view due to cataract, vitreous hemorrhage, and/or retinal tear/detachment, a B scan may be ordered to better evaluate the back of the eye. B scan utilizes sound waves that produce 2D images of the ocular structures. Sound waves are able to bypass dense pathology that may be obstructing a clear view into the eye. As the B scan is also able to visualize the orbit and eye muscles, your physician may order this test to rule out ocular inflamn1ation. What to.£!1!ect during a B-scan ultrasound examination? B scan ultrasound is a non-invasive diagnostic test. During the B scan, the technician will seat the patient in a laid-back position. The patient's eyes will be closed as they feel the soft pressure of an ultrasound probe resting on their eyelid. The safe, ultrasonic imaging waves will be able to bypass any poor view from pathology such as hemorrhage or cataract and will ensure high quality images of the posterior segment are captured. The B scan ultrasound takes about I5 minutes to complete. The images captured directly influence plan of care. The ophthalmologist will discuss with patient which course of treatment is best after reviewing ultrasound results. CamScanner Vitreou.s h.e m.o rrhage 1 ,~ :r,.l I I ~ ~ · ~. r.· 1 " ~ '· ·' 'I'..... ,- I. ' :.. \ CamScanner ¾;UP riJ TJ An is a non-invasive diagnostic modality to in1age the corneal endothelium. It allows detailed in vivo analysis of corneal endothelium in healthy and diseased eyes. Specular microscopy helps in the diagnosis and management of several endothelial pathologies. The ability to properly diagnose and treat corneal endothelial dystrophjes allows ophthalmologjsts to provide a high level of care. Knowing the integrity of the endothelium is another useful tool in a cornea and contact lens practice. In additio~ it can explain seemingly idiopathic decreases in vision by revealing subclinical corneal issues. Taking an endothelial cell count can be helpful before referring patients for cataract or refractive surgery so that any potential endothelial dysfunction or thinning is recogruzed before they have the surgical intervention. 276 NUM 244 2787 CD 2665 359 AVG 375 128 SD 144 36 CV 38 1056 Max 1052 85 Min 101 44 6A 39 531 CCT 519 ~=-- l(.JNAN ~ --=--- - ~u ? CD is a measurement of cell density in mm2 and decreases with age. (See "Average Cell Densities by Age.") A low CD value for a particular age may indicate that the endothelium is depleting faster than normal. CV represents the coefficient, or degree, of variation in the sizes of the endothelial cells (polymegethism). By measuring the variation in size between endothelial cells, the system can measure how much cell loss is occurring. A CV less than 40 is nonnal. HEX indicates the variability in hexagonal cell shape over time. Hexagonality above 50% is suggested to be normal. CamScanner  Cornea Endothelium. ,!. · ~,, ·.,. I t I I (. 't ' I '. \~, ,' f 'ti-I I I. f\ - , >t II l I' ,,...), t r.', Normal Endothelium Very Low Density Polymegethism Stage 3 Guttata High Cell Density High Surgical Risk EW Contact Lenses Normal Cell Count Corneal Guttata r -. r ' rj\ ] I. The Cornea Cell Density & Morphology Changes The corneal endothelium is a single layer of cells whose function is to maintain the Endothelial cells may be lost due to traumatic balance of fluid {aqueous) within the injury, damage during eye surgery (corneal cornea by means of a barrier effect, and incisions, phaco-energy), laser surgery, to remove excess aqueous from the intraocular lenses, pharmaceutical agents cornea by means of a pumping contained in eye drops, or simply through the mechanism. A properly functioning aging process. The number of cells along with endothelium maintains the correct the variance of the sizes and shapes of the clarity and shape of the corneal required endothelial cells serve as quantitative and for clear vision. When endothelial cells qualitative indicators of the health of the are lost or damaged, the remaining cells cornea. With the prevalence of corneal and grow in size and change shape to fill in anterior segment surgeries, implantable eye the gaps in order to maintain structural devices, and contact lenses, the value of integrity. If too many cells are lost or monitoring the corneal endothelium has damaged, the pumping mechanism never been higher. Kenon's specular may be negatively affected, resulting in microscope makes it possible to observe the corneal edema which may lead to endothelium at high magnification and partial or complete loss of vision. provides a detailed assessment of the cornea. This important information helps define the best mode of surgery or therapy for a given patient. CamScanner With a series of unique algorithms and displays, the iTrace Visual Analysis can objectively separate visual performance between the cornea and the lens, allowing doctors to see exactly what their patients are seeing, and use that information to make better treatment decisions. It also aids in choosing the best type of implant for cataract surgery - standard, toric or multifocal. Oysfllltt1ona1Less Pabe,t 015Play ;Trace. ~ur. The iTrace helps physicians better understand where patients' visual symptoms and complaints are coming from. Blur, double-vision, glare, halo, night myopia, and starbursts stem from higher-order aberrations, like Coma, Spherical Aberration, and Trefoil. Before addressing these visual impairments, you need to identify whether the aberrations are in the cornea or the internal optics. Using the iTrace, practitioners can quickly and accurately identify whether symptoms are caused by the cornea or the lens before recommending CamScanner  IA '- ' th I ' There is an advanced technology called the OCULUS Keratograph® SM. It helps Ophthalmologist and Optometrists in accurately ' diagnosing th-e Dry Eye Syndrome and documenting the findings. If treatment is necessary, the Keratograph® SM can compare the before and after treatment results to evaluate the success ot the treatment. CQi,~iJJ1iijty gjtflJclJ ~tll~!flJt~tyt Qf itlhJ~ t:~aJr vmrmJ To measure the quality and stability of the tear film, the OCULUS Keratograph® SM measures the tear film break up time non-invasiveiy. This test takes less than 30 seconds and does not require touching the eye. To evaluate the quantity of tf- tear film, the Keratograph® SM takes a picture of the lower eyelid to measure the tear meniscus height. _ _ _ _ _..i.- "'. Tear fi lm quality before and after dry eye treatment lLupudl iL@y~r The Keratoeraph® SM can document a movie of the oilv laver of the tear film. A healthv and thick lioid laver is colorful anc protects the tears from fast evaporation. If there is not enough lipid, the tear film becomes unstable, the moisture dissipates quickly and bolh vision and co mfort can be compromised. IMIJ~ij~@itr~~thJ,yt '~'ij Located in both upper and lower lids, the meibomian glands produce con-ipl~ oils ti.at- stabili-zei:he tea,- film ar1d preven-t. tear evaporation. If the meibomian glands do not function properly dry eye usually occurs. Your doctor can utilize the advanced feature~oflhe Keralograph :: SM lo di rec1iy asS\:SS the health of vour meibomian R:lands..J Healthy meibomian glands (left), Meibomian gland d-ysfunction lright' CamScanner An objective and quantitative point-of-care diagnostic test that.orovides orecise. ,md oredictive informrltion. ' The Tearlab Os111olarity System* is intended to measure the osmolarity of human tears to aid in the diagnosis of dry eye disease in patients suspected of having dry eye disease, in conjunction with other methods of clinical evaluation. Osmolarity: What the numbers reveal Tear osmolarity is informative when the results are abnormal or normal. Abnormal Osmolarity is defined by: C An elevated reading, >300 mOsm/L, indicating loss of homeostasis. 0 oR, When the inter-eye difference is >8 mOsm/L, indicating instability of the tear film. !Vi Cl Mocie r2te ( = - -- -~ - - - -za;: _ _A_§I_I - 1- ~-C!- ~ -~ 3l 0 -320 3-lO ABNORMAL OSMOU\AITY NORMAL OSMOLA81TY OD OS ~~ INTER-EYE DIFFERENCE INTER-EYE DIFFERENCE 30 1110' 111/L CamScanner  learun lismolarity System (AA\ Tcarlab Control ~ Solutions TearlahElectronic Check Cards Osmolarity Test Pen How it works The Tearlab Osmolarity Test Card, in conjunction with the Tea rlab Osmolarity System, provides a quick and simple method for determining tear osmolarity using nanoliter (nl) volumes of tear fluid collected directly from the eyelid margin. The Test Card is held by the Osmol arity Test Pen, for safe collection. The Tearlab Osmolarity Test utilizes a temperature-corrected impedance measurement to provide an indirect assessment of osmolarity. After applying a lot-specific calibration curve, osmolarity is calculated and displayed as a rLu ~ ---tit~-iv:_;um_ :c_a~va_l:~..-\o_·_ ·_(D.__,.._~-r. --... c.-~...,....... ; ~- ; ____. _- - - - - -~.. ,......... , -~·~·;~.~~1:F '. ~:l.::,\' ,. / r. ~:~. ·/~"";~ ";.,. ~~~~ ~ ~ \j.· JA '. ,~ ti A1:..1 ~ ~·j ' " '- 1,.,"-"'J ""7> and~,...._. t~ ! VQ.Jd L'-.' II ' ~ Tearl,\ti:>c:: tinhth, nr r, ,hhinn thi:> P\ti:>c:: rh ,rinn thi:> ti:>c::t r.::ln r.::l11c::i:> \ ~b~~r~al· te~t r~~~lts~ · - - J - - V - - - - - - - - I II After 5 minutes, the doctor removes the paper and measures how much of it has become moist. II I 1-1n,1t1 tn Pr~n~r~ fnr th~ T~ct I Results I Y~u-w~I; b; ;s~ed t;;ie~~;y;u;~la;~~;or ~;t;c; I l,~uffi