Dr Ben Wild Overview Eye movements are controlled by 6 extra-ocular muscles. The superior rectus pulls the eye upwards, the inferior rectus pulls the eye downwards, the lateral rectus pulls the eye outwards and the medial rectus pulls the eye inwards. The superior oblique muscle connects to the eye after passing through a pulley called the trochlea and is mainly responsible for rotating the eye inwards and pushing the eye downwards. The inferior oblique follows a similar path as the superior oblique, except underneath the eye and does not travel through a pulley system. A frontal image of a right eye with the extra-ocular muscles. If any of these muscles are too tight, too loose, too strong or too weak, there is the potential for an eye turn (strabismus). Esotropia is a type of strabismus (eye turn) where one eye is seen crossing inwards compared to the other but all of the eye muscles still have full range of motion. There are many different causes of esotropia and each has a different treatment and prognosis. Infantile esotropia is made apparent within the first 6 months after birth in an otherwise healthy child. Accommodative esotropia usually presents around 3-4 years old and is due to either uncorrected farsightedness or the accommodative system working too hard to see up close. Consecutive esotropia may occur after a surgery to correct the eye turn. Other types include basic esotropia that can develop at any age, convergence excess esotropia where the eye turn is only noticed when looking at something close, and divergent insufficiency esotropia where the eye turn is only noticed when looking far away. A normal pair of eyes looking off into the distance. An image showing the right eye is turned inwards. This is an esotropia style of strabismus. Signs and Symptoms Signs One eye is turned inwards compared to the other. It may be constant or intermittent (comes and goes), it may be dependent on where the patient is looking, it may just be one eye or it may alternate eyes. Symptoms Possible double vision, lack of depth perception. Causes and Risk Factors Causes Birth anomalies, uncorrected farsightedness, developmental delays. Risk Factors Family history of strabismus. Prevention and Treatment Prevention 1st eye exam around 1 year old followed by another at 3-4 years old to ensure proper development of the eyes and eye muscles. Treatments · Glasses or contacts after a cycloplegic refraction (prescription done after dilating drops). · Treat any amblyopia (lazy eye) by patching the good eye 2hrs/day to full time. · Vision therapy (eye exercises to regain proper eye muscle control). · Surgery by age of 1 or 2 if born with strabismus or upon 1st discovering a strabismus is constant (doesn’t come and go). Prognosis If born with strabismus, surgery can align the eyes but the patient may need several re-alignment surgeries in their lifetime. There is also only a slim chance of gaining depth perception. If the strabismus develops after the age of 3-4, full glasses prescription and vision therapy can often correct the alignment issue, and if not, surgery can re-align the eyes. Regaining depth perception in this case is likely but not promised.

Dr Ben Wild Overview Our vision comes from light waves stimulating retinal photoreceptors and these photoreceptors transferring their signals through a multitude of other cells in the retina to the ganglion nerve cells, then the optic nerve, then to the brain. To help keep these photoreceptors healthy, there are 2 sources of blood flow. One is behind the eye located in the choroid and the other is inside the eye either resting on or inside the retina. Both of these sources represent very strong blood vessels that help create the blood-retinal barrier. A sagittal view of a healthy eye. The Valsalva maneuver occurs when the body blocks or restricts the release of an exhale despite the inner muscles contracting to exhale. This leads to increased abdominal and thoracic (chest) pressure. This phenomenon occurs when someone is lifting something heavy, blowing balloons (resistance from balloons blocking full exhale), having a difficult time on the toilet, vomiting, heavy sneezing, etc. Valsalva retinopathy occurs when the pressure build up is so great that it pops a blood vessel on or inside the retina. This can cause a large pool of blood on the retina or in the vitreous humor (clear gel inside the eye). A sagittal view of an eye with a vitreous hemorrhage (many tiny red blood cells) and a pre-retinal hemorrhage (larger pool of blood at the back of the eye). Signs and Symptoms Signs Hemorrhage (pool of blood) on the retina or blood cells floating inside the vitreous humor. Symptoms Sudden blurry vision, many small orange/red floaters, large dark spot in vision. Causes and Risk Factors Causes Increased abdominal and thoracic pressure leading to increased blood pressure in the head and a popped blood vessel. Risk Factors Physical strain: lifting heavy objects, constipation, vomiting, heavy sneezing, blowing balloons, etc. Prevention and Treatment Prevention Avoid strenuous activities. Treatments · Monitor since the blood will be re-absorbed on its own. · In cases where the blood is encapsulated by a thick membrane, a laser can be used to pop the membrane. Prognosis Full return to normal vision is almost guaranteed. This may take a week or a few months.

Dr Ben Wild Overview Hypertension, or high blood pressure, refers to a condition where the pressure of the blood pushing outwards onto the artery walls is elevated. The pressure is measured in millimeters of mercury with normal levels being under 120mmHg when the heart has just finished a beat, and under 80mmHg right before the heart beats. Stage 1 hypertension starts at 130/81mmHg. When pressures are 180/120mmHg or higher, this is an emergency. If left untreated, hypertension can lead to heart attack, stroke, heart failure, kidney problems and other health conditions. A frontal view of a healthy retina. The most common effect of hypertension on the eyes is hypertensive retinopathy. The constantly high pressure damages the muscles of the arteries. The arteries may then start to shrink, start to block off veins where the arteries and veins cross over each other, start to leak fluid, lead to areas of the retina that lack oxygen, and even swelling of the optic nerve and brain. A frontal view of a retina with hypertensive retinopathy showing swelling of the optic nerve (yellow circle), hemorrhaging around the nerve, cholesterol and fluid leaking into the macula (yellow spots in dark circle), thin arteries, and copper/silver wire appearance to arteries. The second most common effect is weakened blood vessels at the front of the eye and a higher occurrence of subconjunctival hemorrhages (popped blood vessels on the whites of the eye). A frontal view of a healthy eye (top) and an eye with a subconjunctival hemorrhage (bottom). Less common effects can include damage to the nerves that control the extra-ocular eye muscles responsible for eye movement, retinal detachments from leaking fluid, and others. Signs and Symptoms Signs Narrow retinal arteries, whitening of retinal arteries, arteries blocking underlying retinal veins, bleeding in the retina, fluid leaking into the retina, cholesterol leaking into the retina, swollen optic nerves, white patch of the retina that look like cotton wool, popped blood vessels on the front of the eye, restricted eye movements. Symptoms Often asymptomatic, possibly double vision, decreased vision, floaters. Causes and Risk Factors Causes Primary hypertension does not have a known cause and gradually progresses over time. Plaque build-up on arterial walls (atherosclerosis) is seen. Secondary hypertension could be from medications, adrenal gland tumors, congenital (birth defect) heart defect, kidney disease, sleep apnea, thyroid problems, unhealthy lifestyle and diet. Risk Factors Older age, African ancestry, family history, being overweight, lack of exercise, tobacco/vaping, excessive salt consumption, low potassium, too much alcohol, stress, pregnancy, and more. Prevention and Treatment Prevention Maintaining a healthy lifestyle with a balanced and nutritious diet. Treatments · Anti-hypertensive medications. · For double vision: temporary prism on glasses or patch one eye. · For subconjunctival hemorrhage : artificial tears for comfort. · For retinopathy: usually no further treatment required but for persistent fluid leakage; anti-VEGF injections, non-steroidal anti-inflammatory eye drops. Prognosis Hypertension is very common. It increases the risks of heart attack, stroke, heart failure, kidney problems and other health conditions. Proper treatment can decrease those risks. Most of the effects of hypertension on the eye do not cause any visual disturbances and those that do, are usually not permanent if treated in a timely manner.

Dr Ben Wild Overview The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision. A frontal view of a healthy eye fundus (back of the eye) where the macula is the dark circle. An epiretinal membrane (ERM) is formed due to an event that causes the dislocation of glial cells, which normally reside in the inner layers of the retina and optic nerve, and subsequent glial cell multiplication and growth on top of the retina. These cells band together to create a membrane that resembles plastic, or cellophane, wrap. Other names for this condition include cellophane maculopathy and macular pucker. If this membrane continue to thicken, it can pull the retina in many different ways leading to the wrinkling of the retina and macula and can distort vision. A frontal view of an eye with an epiretinal membrane showing wrinkling of the macula and blood vessels. Signs and Symptoms Signs Translucent membrane on retina, wrinkling of the retina and blood vessels on the retina, partial retinal hole, and rarely, hemorrhages (bleeding). Symptoms Often asymptomatic, possible blurry vision, distorted vision (straight lines appear to bend). Causes and Risk Factors Causes Dislocation and growth of glial cells on top of the retina, more specifically, the macula. They are often idiopathic (no known cause) but there are many events that can lead to the formation of an ERM (see risk factors). Risk Factors Intra-ocular inflammation (inflammation inside the eye such as uveitis or vasculitis), intra-ocular surgery ( cataract surgery, retinal surgery, etc.), posterior vitreous detachments , retinal hole formation , retinal tear formation , retinal detachments , retinal dystrophies. Prevention and Treatment Prevention There are no known preventative measures. Treatments · Majority of cases do not need treatment as they often do not affect vision or only affect vision minimally. · Membrane peel surgery and vitrectomy (removal of the vitreous humor gel inside the eye). Prognosis In most cases, epiretinal membranes do not need treatment and vision remains strong. If vision is affected, surgery has been shown to improve vision by at least 2 lines on a reading chart in 75% of cases, produce no benefit in 23% of cases and actually leads to poorer vision in 2% of cases.

Dr Ben Wild Overview The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision. For light to be detected, it must pass through the cornea, pupil, lens and vitreous humor gel before arriving at the retina and/or macula. A frontal view of a healthy eye fundus (back of the eye) where the macula represents the darker circles. A macular hole is a fairly common cause of central vision loss and occurs in 3 out of every 1000 people. It usually occurs due to the tractional pulling forces of the vitreous gel on the fovea (center of the macula) before or during a p osterior vitreous detachment (PVD) . Having had one in one eye gives the patient a 10% chance of also getting one in the other eye at a later date. A frontal view of an eye with a macular hole (red dot). Quickly, a PVD occurs once the vitreous gel has liquified and has shrunk enough that it separates from the retina at the back of the eye. This is a normal event that occurs once in both eyes. The separation can sometimes pull the retina so hard the retina tears or pulls the macula so hard it causes a macular hole. Other reasons for pulling forces to exist between the gel and the macula include high levels of myopia (nearsightedness) , and trauma. Signs and Symptoms Signs Red circular hole in the middle of the macula. Symptoms Starts as distortion in central vision (metamorphopsia). Then progresses to a blind spot in the central vision of one eye. Sometimes this can occur asymptomatically if the patient never covers the fellow eye. Causes and Risk Factors Causes Vitreous gel pulling the retina causing a hole. Risk Factors Female, age 60-70, vitreomacular traction from impending posterior vitreous detachment , high levels of myopia (eye is stretched) . Prevention and Treatment Prevention There are no known preventative measures. Treatments · A partial hole is usually just observed. The majority will resolve on their own after the posterior vitreous detachment has completed. · Vitreolysis using enzymes to digest the proteins holding the gel to the retina. · Vitrectomy surgery to remove the vitreous gel completely and insertion of a silicone or gas bubble to push the retina together (the patient lies face down for the bubble to push the retina back together). Prognosis Most partial holes resolve on their own without treatment. For macular holes requiring surgery, the hole is closed in almost 100% of cases and vison improves in 80-90% of cases. 20/40 vision or better is regained in 65% of cases. Note: 20/40 vision means letters must be twice as large as 20/20 vision.

Dr Ben Wild Overview Diabetes is a disorder that leads to elevated levels of glucose (sugar) in the blood. This excess sugar can damage the blood vessels of the body and lead to heart damage, kidney damage, nerve damage and many eye issues. A frontal view of a healthy retina and optic nerve. When it comes to the eyes, diabetes can lead to blindness several different ways. Common changes to the eye include rapidly changing prescriptions (dependent on blood glucose levels), thinning of the iris (loss of iris color), and retinopathy (damage to the retina). Other less common issues include styes , xanthelasma , early cataracts , glaucoma , optic nerve swelling and nerve palsies. A frontal view of a retina showing neovascularization (growth of small blood vessels), retinal hemorrhaging (areas of bleeding in the retina), cholesterol plaques (yellow plaques in the retina), and a swollen optic nerve. Diabetic retinopathy can be seen in up to 40% of all diabetics at some point in their lives and is sight threatening 10% of the time. Diabetic papillopathy refers to a diabetic state where the optic nerves are no longer receiving enough oxygen and start to swell. This is unilateral (in one eye) 50% of the time. This is a very poorly understood condition. Signs and Symptoms Signs Diabetic retinopathy Bleeding in the retina, aneurysms of retinal blood vessels, swelling, cholesterol plaques, neovascularization (growth of fragile leaky blood vessels), retinal detachment, etc. Diabetic papillopathy Red optic nerves, swollen blood vessels around the optic nerves, swollen nerves. Symptoms Diabetic retinopathy Blurry vision, blind spots, black spots in vision. Diabetic papillopathy Can be asymptomatic, can show mild blurry vision. Causes and Risk Factors Causes Progressive damage to small blood vessels due to elevated blood glucose. Risk Factors (for developing eye complications from diabetes) Longer duration of diabetes, poor blood glucose control, pregnancy (can make retinopathy temporarily worse), high blood pressure , nerve damage, high cholesterol, smoking, obesity, previous cataract surgery. Prevention and Treatment Prevention Maintaining a healthy lifestyle with a balanced and nutritious diet. Treatments · Manage diabetes: o Review current management to improve blood glucose stability. o Treat high blood pressure and high cholesterol if present. o Stop smoking. · Treat diabetic eye disease: o Anti-VEGF injections. o Steroid injections. o Laser photocoagulation. Prognosis The younger a person is when they get diabetes the worse the outcomes become for not just their eyes but their entire body. For example, proliferative diabetic retinopathy (when small, fragile, blood vessels start growing into the retina) is a late stage of diabetic eye disease and signifies vision loss is likely in the near future. Only about 5% of diabetic retinopathy cases are considered to be proliferative. Unfortunately, up to 90% of people who have had diabetes for 30+ years are likely to have signs of proliferative diabetic retinopathy. Therefore, living a healthy lifestyle for as long as possible is key to preserving vision. If diabetes is diagnosed but no eye damage is seen, treating the elevated blood glucose, high blood pressure and high cholesterol, quitting smoking, and losing weight, can dramatically increase the amount of years the diabetes will take to damage the eyes. Current treatments can further prolong good vision but cannot stop the eventual damage from occurring.

Dr Ben Wild Overview Our vision comes from light waves stimulating retinal photoreceptors and these photoreceptors transferring their signals through a multitude of other cells to the ganglion nerve cells then to the brain. To help keep these photoreceptors healthy, there are 2 sources of blood flow. One is behind the eye located in the choroid and the other is inside the eye either resting on or inside the retina. Both of these sources represent very strong blood vessels that help create the blood-retinal barrier. A frontal view of a healthy retina. A retinal vein occlusion occurs when one of the veins that extends into the eye is blocked. This usually occurs due to health conditions that cause arteries to thicken (atherosclerosis) which leads to veins being compresses at cross over points. When a vein is blocked, the pressure inside the vessel increases, blood flow stops, and the retina may become oxygen deprived (hypoxic). Fluid then starts to leak into the retina. A frontal view of a retina with a central retinal vein occlusion (top) showing a swollen optic nerve and retinal hemorrhaging all over and a branch retinal vein occlusion (bottom) where the vein is occluded by an artery crossing overtop, retinal hemorrhages are noticed and the vein is white. If the blockage occurs inside the optic nerve it is called a central retinal vein occlusion (CRVO) and affects the entire field of view, if it occurs in a vein on the retina it is called a branch retinal vein occlusion (BRVO) and affects only the part of the visual field corresponding to where the vein was occluded. If blood flow is completely stopped, the vein occlusion is deemed ischemic, and if it is partially blocked, it is deemed non-ischemic. Signs and Symptoms Signs CRVO Absent or mild effect on pupil reactivity, dilated veins, bleeding in the retina, cotton wool spots in the retina (indicating lack of oxygen), swollen retina, swollen optic nerve. BRVO Dilated veins, bleeding in the retina, cotton wool spots in the retina (indicating lack of oxygen), may see plaque in the vein, swollen retina. Symptoms CRVO Sudden painless vision loss, black/dark red spots in vision. BRVO Often no symptoms, sometimes sudden painless blurred and/or distorted vision, black/dark red spots in vision. Causes and Risk Factors Causes Blocked retinal vein. Risk Factors Age (over 65), high blood pressure , high cholesterol, diabetes , glaucoma/elevated eye pressure , oral contraceptives, smoking, dehydration, kidney failure, inflammatory autoimmune disease. Prevention and Treatment Prevention Avoid all cardiovascular risk factors ( high blood pressure , diabetes , etc.), avoid smoking, avoid oral contraception. Treatments · Monitor the eye while doing a full stroke work up including blood pressure testing, blood viscosity testing, complete blood count, random glucose, and cholesterol. If this occurs multiple times or in both eyes, also include chest x-ray, homocysteine levels, rheumatoid factor, anti-nuclear antigen, carotid artery imaging, adenosine, angiotensin-converting enzyme, and antineutrophilic cytoplasmic antibody. · If vision is worse than 20/30 o Anti-VEGF injections. o Steroid injections or implant. · If blood vessels grow into the retina o Same as above o Laser photocoagulation. Prognosis If there is an ischemic (total blockage) CRVO, the possibility of full recovery is low due to the high likelihood of macular degeneration , glaucoma and/or optic nerve damage in. Non-ischemic CRVOs often resolve on their own within 6-12 months sometimes with permanent retinal bleeding and blood vessel scarring but usually do not affect long-term vision. Ischemic and non-ischemic BRVOs resolve on their own within 6-12 months, however, the retina does experience oxygen deprivation for several weeks or months. This can stimulate the growth of blood vessels (neovascularization) into the retina and/or iris and cause glaucoma 3 months after the vein occlusion in 8% of cases.

Dr Ben Wild Overview The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision. For light to focus on the macula, it must pass through the cornea (front of the eye), pupil, lens and finally, vitreous humor gel. A frontal view of a healthy eye fundus (back of the eye) where the macula represents the darker circle. Vitreomacular traction (VMT) occurs during an impending posterior vitreous detachment (PVD) . Briefly, a PVD occurs due to the liquification and shrinkage of the vitreous gel that inflates the eye. This process is a normal part of ageing. Eventually, the gel shrinks enough that it separates from the retina. VMT occurs when the gel is still attached to the retina but is in the process of pulling away. A frontal view of an eye with a lamellar hole caused by vitreomacular traction. Signs and Symptoms Signs Pseudo-cyst formation only visible on specialized imaging, lamellar macular holes (holes comprising of only a few retinal layers), and blood vessel leakage. Symptoms Often asymptomatic (no symptoms), sometimes decreased vision, light flashes, distorted vision. Causes and Risk Factors Causes Vitreous gel pulling on the macula. Risk Factors Impending PVD . Prevention and Treatment Prevention There are no known preventative measures. Treatments · Majority of cases do not need treatment as they often do not affect vision or only affect vision minimally and resolve on their own. · Vitreolysis (inject an enzyme that separates the vitreous gel from the retina). · Vitrectomy (removal of the vitreous gel). Prognosis In most cases, VMT resolves on its own after the completion of the PVD . If an epiretinal membrane has formed on the retina, surgery may be required to manually separate the retina from the vitreous gel although this is very rare. Overall, this condition is unlikely to affect vision long-term.

Dr Ben Wild Overview The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision. A frontal view of a healthy eye fundus (back of the eye) where the macula represents the dark circle. Solar retinopathy occurs when photoreceptors absorb intense solar radiation (light from the sun) and burst. These micro-explosions usually start a few hours after exposure to intense light (could also be from welding or other intense light sources). A frontal view of an eye with a lamellar hole caused by solar retinopathy. Signs and Symptoms Signs A yellow or red fovea (center of the macula) that may progress into a macular lamellar hole (hole several retinal layers thick), thinning fovea. Symptoms Central blind spot, variable vision loss. Causes and Risk Factors Causes Looking at intense light such as the sun. Risk Factors See causes. Prevention and Treatment Prevention Wear welding level eye protection for welding or for observing solar eclipses. View eclipses indirectly via cell phone. Treatments · There are no treatments available. Prognosis A full recover occurs in the vast majority of cases. The likelihood of recovery depends on the intensity and duration of the light stimulus. In some cases, recovery takes a full 6 months. In rare cases, permanent central vision loss occurs.

Dr Ben Wild Overview The retina is located at the back surface of the inside of the eye. Its main function is to detect and transmit the sensation of light to the brain for interpretation. Clinically, the macula refers to the part of the retina that represents the finely detailed central vision. A frontal view of a healthy eye fundus (back of the eye) where the macula represents the dark circle. Central serous retinopathy (CSR) is still a poorly understood condition without any known cause but has been highly associated with high levels of cortisol which occurs during times of high stress. It represents a condition where a large area of swelling occurs under the macula of one eye. It is extremely rare for it to occur in both eyes. This swelling can change color perception, can cause a noticeable spot in the central vision, can decrease vision and distort vision and can sometimes make someone more farsighted. A frontal view of an eye with swelling caused by CSR. Signs and Symptoms Signs Area of swelling underneath the retina sometimes only visible with specialized machinery. Symptoms Unilateral (one eye) blurred vision, unilateral change in color vision, distorted vision. Causes and Risk Factors Causes Unknown. Risk Factors Use of corticosteroids, type A personality, high stress, Cushing’s syndrome, pregnancy, sleep apnea, helicobacter pylori infection. Prevention and Treatment Prevention There are no known preventative measures other than living a low stress lifestyle. Treatments · In most cases, no treatment is required. · Steroid eye injection. · Laser photodynamic therapy. · Anti-VEGF eye injection. · Aspirin has shown mixed results. · Beta-blockers. Prognosis 80% of the time, CSR spontaneously resolves within 3-6 months without treatment. In other cases, treatment is needed for resolution. CSR can reoccur in up to 50% of patients. If CSR remains unresolved after 12 months, permanent damage can occur.

Dr Ben Wild Overview Prescription eye glasses are designed to help the eyes focus light on the retina (the posterior surface of the inside of the eye that detects light). If the eyes are perfectly focused together, there is no need for prescription eye glasses. Non-prescription glasses such as non-prescription blue blocking glasses or non-prescription sunglasses do not provide any focusing power. Example 1) OD refers to Oculus Dexter or right eye, OS refers to Oculus Sinister or left eye 2) The sphere, on a superficial level, describes whether someone is nearsighted (trouble seeing distant objects without glasses) or farsighted (someone who strains to see up close). Minus (-) means nearsighted, plus (+) means farsighted. The number behind the (-) or (+) indicates severity. Plano (0) to -3.00 is considered mild nearsightedness, -3.00 to -6.00 is considered moderate and over -6.00 is considered high. (0) to +1.50 is considered mild farsightedness, +1.50 to +3.50 is considered moderate, and over +3.50 is considered high. 3) Cylinder refers to how much astigmatism (eye is in the shape of a cylinder instead of a sphere) is being corrected by the glasses. Optometrists always use the minus (-) form and ophthalmologists often use (+) form. Either way, the number behind the (-) or (+) describes the severity of astigmatism. (0) to -1.25 is considered mild, -1.25 to -2.25 is considered moderate and over -2.25 is considered high. 4) The axis refers to the direction of the cylinder. When holding a cylinder, it could be at 0 (180 would be the same) degrees or could be turned to any angle from 0 to 179 degrees. 5) Add, or additional, power refers to how much power on top of the distance prescription is needed to help with near vision. This usually only applies in cases of accommodative dysfunction or presbyopia (both conditions describing the inability to change focus from far to near) 6) Prism is a rare finding in a prescription. Prisms bend light. Changing the direction of light can help alleviate eye strain in certain patients or can alleviate symptoms of double vision in other patients. Prism can be edged into a lens base out (base towards ears), base in (base towards nose), base up, base down or in any direction. Interestingly, recent research has shown that in certain cases of poor balance due to concussion or traumatic brain injury, prisms can instantaneously help a patient walk upright and straight again. 7) The note section usually shows how long a prescription remains valid. In patients with certain eyes diseases that tend to progress rapidly or in children the prescriptions are usually only valid for 1 year. In healthy patients whose prescriptions haven't changed much in years, prescriptions are usually valid for 2 years. Other notes could include what type of lenses are required (progressives, bifocals, distance only, near only, etc.), refractive index of the lens (how dense the glass or plastic lens is), and/or lens coating recommendation (whether it's scratch resistant, UV blocking, blue blocking, or anti-reflective).

Dr Ben Wild Overview Our vision comes from light waves stimulating retinal photoreceptors and these photoreceptors transferring their signals through a multitude of other cells to the ganglion nerve cells then to the brain. To help keep these photoreceptors healthy, there are 2 sources of blood flow. One is behind the eye located in the choroid and the other is inside the eye either resting on or inside the retina. Both of these sources represent very strong blood vessels that help create the blood-retinal barrier. A frontal view of a healthy retina. A retinal artery occlusion occurs when one of the arteries that extends into the eye is blocked. This usually occurs due to health conditions that cause arteries to thicken (atherosclerosis). If this thickening occurs outside of the eye, a piece of debris (cholesterol plaque) can break off and clog a retinal artery (embolism). If it occurs in a retinal blood vessel, a cholesterol plaque can clog that vessel (thrombosis). When an artery is blocked, blood flow stops and the retina may become completely oxygen deprived (anoxic) and turns white. Unlike with a vein occlusion, fluid does not start to leak into the retina. If the blockage occurs inside the optic nerve, it is termed a central retinal artery occlusion (CRAO) and if the blockage occurs in an artery on the retina, it is termed a branch retinal artery occlusion (BRAO). CRAOs cause complete vision loss whereas BRAOs cause a blind spot corresponding to where the blockage lies. A frontal view of a retina with a CRAO (top) showing a white retina and red macula, and a BRAO (bottom) showing a yellow embolism/thrombosis and retinal whitening around the occlusion. Signs and Symptoms Signs CRAO Pupil non-reactive to light, no light perception vision, cherry red spot in retina (retina is white except the macula that is red), rare retinal bleed, in 20% of cases a visible embolism or thrombosis, whitening of blood vessels after a few days, optic nerve death after a few days, rare small blood vessel growth. BRAO Pupil mildly reactive to light, large blind spot in vision, thin retinal arteries, white retina around the occlusion, visible embolism/thrombosis. Symptoms CRAO Sudden painless severe vision loss to no light perception. BRAO Sudden painless vision loss, blind spot in area corresponding to where the BRAO occurred. Causes and Risk Factors Causes Blocked retinal artery. Risk Factors Giant cell arteritis, systemic lupus erythematosus, granulomatosis with polyangiitis, vasopasms (migraines), low blood pressure, hyperhomocysteinemia, sickle cell disease, antiphospholipid antibody syndrome, high blood pressure, high cholesterol, diabetes , more. Prevention and Treatment Prevention Avoid all cardiovascular risk factors ( high blood pressure , diabetes , etc.), avoid smoking. Treatments · Monitor the eye while doing an urgent (within 24 hours) full stroke work up including assessing pulse, blood pressure, blood viscosity, complete blood count, random glucose, cholesterol, testing for giant cell arteritis. Other testing may include carotid artery imaging, electrocardiogram, chest x-ray, and more. · CRAO: o Panretinal photocoagulation laser. o Anti-VEGF eye injections. o Review monthly. · BRAO o Lie face up to increase perfusion pressure. o Eye massage. o Glaucoma drops to lower eye pressure. o Increased oxygen. o Laser embolism with YAG. o Discontinue smoking. o Antiplatelet therapy. Prognosis Prognosis depends on the severity of the blockage for both CRAOs and BRAOs. For CRAOs, most patients do not regain vision. Some patients have a cilioretinal artery (artery entering the eye from a different source). These patients may regain some central vision. For BRAOs, vision does not usually improve after the occlusive event. Some BRAOs can lead to severe vision loss while others only small blind spots. Vision loss is dependent on where the occlusion occurred. CRAOs and BRAOs do not typically get worse but vision usually does not improve over time.