Dr Ben Wild 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 sagittal view of a healthy eye (left) and a coronal view of its retina (right). Age-related macular degeneration (AMD) is an irreversible, progressively degenerative condition characterized by a loss of central vision. It is the most common cause of blindness in the developed world and occurs bilaterally (in both eyes), although usually affects one eye more than the other. There are two main types of AMD: 1. Dry AMD represents 90% of cases, typically progresses slowly (over years), and is caused by calcification of retinal waste products which then leads to the decay of the retina. It can progress to wet AMD. 2. Wet AMD occurs in 10% of cases, typically progresses quickly (over months), and is caused by the growth of fragile, leaky, blood vessel networks that disrupt the macula. Dry AMD (left) showing several yellow drusen and one area of geographic atrophy and wet AMD (right) showing drusen and bleeding. Signs Drusen (calcified waste products in the macula), vascular tissue (fragile blood vessels), scar tissue, bleeding, geographic atrophy (patches of decayed retina). Symptoms Decreased vision and contrast sensitivity, central blind spots or dark spots in vision, metamorphopsia (straight lines look warped). Causes The decay of photoreceptors (light sensing cells of the retina) in the macula. Risk Factors Confirmed: old age, Caucasian background, genetics, smoking, high blood pressure, and high fat diets. Possible: sun exposure, blue irises, female, cataract surgery. Prevention Confirmed: foods high in lutein, zeaxanthin, meso-zeaxanthin, and beta-carotene, avoid smoking/2nd hand smoking, avoid vascular conditions such as high blood pressure, diabetes, etc., with a healthy and balanced lifestyle. Possible: lutein/zeaxanthin supplements, sunglasses, omega 3s, 20mg/day of saffron. Treatments Dry AMD · 15mg of lutein and 2mg of zeaxanthin per day may slow progression of early stages. · AREDS/AREDS 2 supplements twice a day for moderate to advanced stages. · Laser photocoagulation for advanced stages. · Up and coming: Lampalizumab injections, subretinal stem cell injections. Wet AMD: · Anti-VEGF injections. · Photodynamic therapy. Advanced AMD · Low vision therapy including quality of life products. · Optical correction with telescopes and magnifiers. · Electronic aids such as voice activated products, computers, etc. No cures exist for AMD, however, with early diagnosis and treatment, vision can be stabilized for years before possibly declining to a legally blind state. Once diagnosed, self monitoring with an AMSLER grid at home can quickly alert the patient to noticeable progression of their AMD and can allow for more timely follow ups with eye care professionals and treatments. The above is an AMSLER Grid as described in the Treatments section above. It is recommended to screen each eye once a day and only takes a few seconds. Try hanging this on your fridge (see below for a link to a printable PDF). How to use the AMSLER grid 1. While wearing the glasses you use to read, hold the grid about 35cm or 6 inches from your face with good lighting. 2. Cover one eye. 3. Look at the central dot with your uncovered eye. 4. While focusing on this dot try to identify if the lines in your central or peripheral vision are blurry, wavy, or missing or if there are stable dark spots. 5. Repeat with the other eye. 6. If you notice any areas on the grid that appear darker, lighter, wavy, blank or blurry, contact your eye doctor right away Below is an example of possible defects on the AMSLER grid. Click below for a printable copy of the Amsler grid.

Dr Ben Wild For vision to be in clear and in focus, light must pass through the cornea, the clear tissue at the front of the eye, the pupil, the black hole in the center of the colored iris, and the lens, the clear tissue inside the eye to the tissue responsible for detecting light, the retina. The lens sits inside a bag (capsule) attached to strings (zonules) that are controlled by muscles (ciliary body). Cataracts refer to the fogging/clouding of the lens. There are many different types of cataracts but the 4 main types are anterior subcapsular cataracts (ASC), nuclear sclerotic cataracts (NSC), cortical cataracts, and posterior subcapsular cataracts (PSC). PSCs tend to be the fastest growing cataract of all. From left to right, healthy lens, ASC, NSC, cortical cataract and PSC. Cataracts are most often age related but systemic (full body) diseases, eye diseases, retinal dystrophies, and trauma can lead to early cataracts. Congenital cataracts (cataracts your are born with) can be due to tuberculosis, rubella, shingles, and other infections during pregnancy, metabolic disorders like Fabry disease, galactosemia and more. Signs Yellow, brown or black lens, white haze or plaque on the lens, bubbles within the lens, or spoke like white haze within the lens. Symptoms Constant blurry vision that cannot be corrected with glasses, glare, difficulty with night vision, difficulty with lots of light (PSC), needing more light to see. Causes The solidification of crystals within the lens. Risk Factors Diabetes, myotonic dystrophy, atopic dermatitis, neurofibromatosis, systemic diseases that cause uveitis (inflammation inside the eye), glaucoma, age, possibly ultra-violet damage, over use of corticosteroids, rubella infection, possibly extended periods of dehydration, high nearsightedness. Prevention Stay hydrated, wear UV blocking glasses, avoid preventable systemic diseases with a healthy and balanced lifestyle. Treatments Cataract surgery when the cataracts start to affect daily activities or when they become too hazy for an eye care professional to properly monitor ocular health. Surgery starts with topical and systemic anesthesia, although the patient usually remains conscious. 2 incisions are made in the cornea and the eye is filled with viscoelastic gel. A small hole is created in the capsule and fluid inserted to dissect the lens from the capsule. The lens is then cut into pieces and vacuumed out. The capsule is inflated with gel and a plastic intra-ocular lens is inserted into that same capsule. Femtosecond cataract surgery involves using a laser to create the incision, the hole in the capsule and to even break up the natural lens for greater precision. 1. Single vision: the surgeon can correct your vision for near or distance but not both. 2. Monovision: Use single vision lenses to correct one eye for distance and one eye for near so that the patient can cope without glasses. This may compromise depth perception. 3. Multifocal: lenses that correct both distance and near prescriptions although fluctuating vision and glare become issues. In most cases, a full recovery of vision is expected as long as there are no other ocular diseases present. Most surgeries proceed without any complications and of those rare cases, most complications are easily manageable. These complications may include allergies to eye drops, elevated eye pressures and glaucoma, uveitis (intra-ocular inflammation or infection), and scarring over of the intra-ocular lens (posterior capsular opacification). Other much less-common complications include retinal detachment, double vision, droopy eyelids, leaking of the vitreous gel, breakage of the zonules that hold the capsule, dislocation of the lens, ripping of the capsule, swelling of the retina, fogging of the cornea and risks associated with anesthesia.

Dr Ben Wild The eyelids are made up of various types of skin, muscle, glands, hair follicles and much more. Their purpose is to protect the eyes from dryness, bright lights and irritants. Frontal view of a healthy eye. Blepharitis is defined as inflammation of the eyelids. It is a common cause of eye discomfort. Blepharitis can be broken down into 4 main types; 1. Staphylococcal. 2. Seborrheic. 3. Demodex . 4. Meibomian gland dysfunction. Staphylococcal blepharitis is caused by bacteria, is usually easily treatable, and can be associated with atopic dermatitis or rosacea. Seborrheic blepharitis is associated with seborrheic dermatitis, can be treated similarly to eczema, and may need a dermatology referral. Demodex mites tend to be very difficult to manage and patients with this type of blepharitis are usually most symptomatic at night or in the morning. Meibomian gland dysfunction (MGD) can occur alongside blepharitis or on its own. There are about 40 tiny meibomian glands per eyelid that secrete oil, similar to cooking oil. This oil protects the watery tears produced by the lacrimal gland. If these glands become inflamed, they start producing toothpaste like secretions leading to dry eyes, blurry vision, and possibly, chalazion (blocked gland) or hordeolum (stye) formation. Front view of an eye with severe blepharitis. Angular blepharitis is a lesser know 5th type of blepharitis located at the outer corner of the eyelids. It is typically due to bacterial or herpes simplex infections, eczema, skin chaffing and/or constant tear overflow. Front view of an eye with angular blepharitis. Signs Crusty eyelashes, red eyelids, red eyes, loss of eyelashes, greasy eyelashes. Symptoms Stinging, burning, gritty, itchy eyes, mild light sensitivity, poor contact lens tolerance, fluctuating vision. Causes Immune reaction to bacteria, eczema, and/or demodex mites. Risk Factors Poor eyelid hygiene. Prevention Proper lid hygiene which involves washing your eyelashes along with face washing. Treatments Common for all: washing lids with baby shampoo, Cetaphil, Blephagel, Systane wipes or other solutions. Hot compresses where you hold a hot face mask to the closed eyelids for 10 minutes followed by massaging your top eyelids downwards and bottom eyelids upwards to clear the meibomian glands, omega 3 supplementation and artificial tear treatments. Condition specific treatments: 1. Staphylococcal: antibiotic ointment or drops, steroid drops, cyclosporin drops. 2. Seborrheic: steroid drops or ointments. 3. Demodex: tea tree oil, radiofrequency, Intense Pulsed Light (IPL) treatment. 4. MGD: tetracycline type pills, Lipiflow treatment. 5. Angular: antibacterial ointment, eyelid surgery. Unfortunately, there is usually no permanent cure for most types of blepharitis. If managed properly, there should be no permanent damage to the eyes or loss of vision. If not managed properly, it can lead to permanent scarring and vision loss.

Dr Ben Wild The eyelids are made up of various types of skin, muscle, glands, hair follicles and much more. The outer skin is the normal, tough, keratinizing skin found all over the body. The inner eyelid skin, known as the palpebral conjunctiva, is more delicate non-keratinizing skin. Concretions are balls of keratinized skin cells and debris that solidify over time and become calcified. They develop underneath the normal non-keratinizing skin. They are usually found on the inside of the lower eyelid but can sometimes be seen on the inside of the upper eyelid. When concretions are small, they are usually covered by functioning skin cells of the palpebral conjunctiva and do not cause any irritation but when they are large, they can break through the layer of conjunctiva and cause irritation. Concretions are very common findings and are associated with ageing and chronic ocular inflammation. Front view with the lower lid pulled downwards exposing yellow concretions. Signs Yellow stone-like balls on the inner eyelids. Symptoms Usually no symptoms but, if they are large, irritation and foreign body sensation. Causes Age. Risk Factors Ocular inflammation like dryness, conjunctivitis, etc. Prevention There are no known preventative measures. Treatments · Artificial tears for comfort. · Removal with a needle after an anesthetic drop is applied. Concretions are very common and usually go unnoticed. They do not threaten vision but can be quite irritating if large. Simple removal removes this irritation although there is a chance that more will grow and also need to be removed.

Dr Ben Wild There are 12 cranial nerves that form the parasympathetic nervous system responsible for controlling the body. Interestingly, most of these nerves affect either the eyes or the eye muscles in some shape or form. There are two 3rd nerves, otherwise known as oculomotor nerves. One controls some muscles around the right eye and the other controls the same muscles around the left eye. Muscles under control of the oculomotor nerve include the levator muscle that raises the top eyelids, the ciliary body muscles that control the ability to change focus, the iris sphincter muscle that shrinks your pupils, the superior, inferior and medial recti muscles responsible for moving the eyes up, down, and inwards, and the inferior oblique muscle responsible for pushing the eye upwards among other things. A healthy pair of eyes looking off into the distance. When the 3rd nerve stops working, called a 3rd nerve palsy, investigations must be done to determine the cause as some causes are life threatening. In some cases, a 3rd nerve palsy may present as a partial palsy (not showing all of the deficiencies in the actions listed above). It can present as just droopy eyelids, with just limited elevation of the eye, with just limited depression of the eye, or with or without enlarged pupils. A right 3rd nerve palsy (eye on left shows a “down and out” appearance, an enlarged pupil, and a droopy eyelid. Frontal view of a right eye with extraocular muscles. Highlighted muscles include the superior rectus, medial rectus, inferior rectus and inferior oblique muscles all of which are all controlled by the 3rd nerve. Signs One eye is turned outwards and downwards, the pupil may or may not be enlarged, droopy eyelid, limited ability to move the eye up, down or inwards. Note: not all of these signs need to be present. Symptoms Vertical and horizontal double vision, loss of near vision. Causes and Risk Factors Without enlarged pupil: vascular diseases like diabetes and high blood pressure, aneurysms, meningiomas, granulomatous inflammation (auto-immune disease related), head trauma, brain tumors, giant cell arteritis. With enlarged pupil: Same as without pupil involvement but more likely a compressive lesion post head trauma or brain aneurysm or brain tumor. Prevention Ensure a healthy lifestyle to avoid vascular issues like high blood pressure, diabetes, etc. Treatments · Needs full neurological work up to identify the cause. If the pupil is enlarged it necessitates a same day work up. · Fresnel or permanent prism in glasses for the double vision. · Patching one eye temporarily for the double vision. · Botox. · Surgery. If the 3rd nerve palsy is due to vascular diseases, this condition does tend to resolve on its own. If not, surgery for the droopy eyelid or double vision may be necessitated. When a 3rd nerve palsy is caused by a compressive lesion like a brain tumor or aneurysm, the nerve tends to regenerate but does so by creating new connections. These can range from the upper eyelid moving upwards when looking down, the pupil shrinking when looking towards the opposite eye, or the eye moving towards the opposite eye when trying to look upwards or downwards. These new connections become permanent even after treatment of the underlying issue.

Dr Ben Wild There are 12 cranial nerves that form the parasympathetic nervous system that controls the body. Interestingly, most of these nerves affect either the eyes or the eye muscles in some shape or form. There are two 4th nerves, otherwise known as trochlear nerves. One controls the superior oblique muscle around the right eye and the other controls that same muscle around the left eye. The superior oblique muscle is responsible for lowering the eye, helping move the eye outwards (towards the ear), and rotating the eyes inwards. When the 4th nerve stops working, aka a 4th nerve palsy, the patient loses control of the superior oblique muscle. This results in sudden vertical double vision which is usually worse when looking towards the normal eye. The double vision usually is lessened with a head tilt towards the shoulder on the same side as the affected eye. A healthy pair of eyes looking off into the distance. A right 4th nerve palsy (eye on left (right eye) shows a elevated appearance). Frontal view of a right eye with attached muscles. The circled muscle represents the superior oblique muscle, which is affected by the 4th nerve palsy. Signs One eye is elevated when compared to the normal eye. This is made worse by looking towards the normal eye. The patient may have a head tilt. Symptoms Vertical double vision that improves when tilting the head towards the opposite shoulder. Causes Idiopathic (unknown), congenital (born with this condition), trauma. Risk Factors Vascular conditions like high blood pressure, diabetes, brain lesions like tumors or aneurysms, head trauma. Prevention Ensure a healthy lifestyle to avoid vascular issues like high blood pressure, diabetes, etc. Treatments · Needs full neurological work up to identify the cause if it presents as suddenly. · Usually spontaneously resolves without treatment unless due to aneurysm or tumor. · Glasses with prism for double vision. · Surgery for double vision or head tilt. In most cases, a 4th nerve palsy resolves on its own. It does require a neurological work up if it occurs suddenly. Symptoms of a 4th nerve palsy can be managed with either surgery or glasses with prism but the underlying cause of the palsy is the more concerning issue.

Dr Ben Wild There are 12 cranial nerves that form the parasympathetic nervous system that controls the body. Interestingly, most of these nerves affect either the eyes or the eye muscles in some shape or form. There are two 6th nerves otherwise known as abducens nerves. One controls a muscle on the right eye and the other controls a muscle on the left eye. The muscles under control of these nerves are responsible for moving the eye laterally towards the ear, a process known as abduction. One, or both, of these nerves can be affected by vascular issues like high blood pressure and/or diabetes, can be affected by elevated pressure within the skull, or can be secondary to a growth. When due to vascular issues, the condition, 90% of the time, resolves on its own in weeks to a few months. When due to a tumor, it will not resolve until the pressure from the tumor is treated. A healthy pair of eyes looking off into the distance. A right 6th nerve palsy (eye on left (right eye) is turned inwards). Frontal view of a right eye with the attached muscles. The square showing which muscle that is affected by a 6th nerve palsy. Signs One eye is turned inwards. This is more obvious when looking in the distance and less when looking up close. Symptoms Double vision especially when looking to the side of the affected nerve and loss of the ability to turn an eye outwards. Causes Loss of function of the abducens nerve whether from lack of oxygenated blood flow or physical pressure. Risk Factors High blood pressure, diabetes, brain tumors, intracranial hypertension, trauma. Prevention Ensure a healthy lifestyle to avoid vascular issues like high blood pressure, diabetes, etc. Treatments · Needs full neurological work up to identify the cause. · An episode can be just monitored since 90% of cases resolve spontaneously in weeks to months. · Fresnel or permanent prism in glasses to correct the double vision. · Patch one eye to eliminate the double vision. · Botox. · Surgery (usually only after 12 months since initial onset). In the vast majority of cases, this condition resolves on its own. After identifying the underlying cause, and after seeking treatment for that cause, it is likely one would regain full use of the nerve and the eye muscle. In rare cases, surgery or prism glasses would be required on an ongoing basis.

Dr Ben Wild The anterior chamber of the eye refers to the space between the cornea (the front clear tissue of the eye) and the iris (the colored part of the eye) where the aqueous humor (the liquid inside the eye resides). This area should be large, and clear of any debris. Front view (left) and sagittal view (right) of a healthy eye. The anterior chamber extends from the front of the lens to the back of the cornea. Anterior uveitis, or iritis, refers to a condition where inflammation localized to the back of the iris (uveal layer) causes fibers and/or white blood cells to leak into the eye. Anterior uveitis can be classified as acute (usually develops quickly, in 1 eye and is the most symptomatic), recurrent (reoccurs after periods of no inflammation lasting over 3 months) or chronic (can present without symptoms, often occurs in both eyes and episodes last over 3 months). It can also be classified as granulomatous (produces clumps or nodules of immune cells) or non-granulomatous. Front view (left) showing redness around the iris and synechiae (areas where the iris is stuck to the lens) and sagittal view (right) showing white blood cells, fibers and the iris stuck to the lens. Signs Symptoms Causes Infections (bacterial, viral, fungal, parasites), auto-immune conditions (rheumatoid arthritis, sarcoidosis, spondyloarthropathies, and many more), cancers, idiopathic (unknown). Risk Factors Ocular inflammation like dryness, conjunctivitis, etc. Prevention There are no known preventative measures. Investigation · If an episode is the 1st time, in one eye, non-granulomatous, and mild to moderate in severity then no investigation required. · Otherwise, test for spondyloarthropathies, syphilis, sarcoidosis, Lyme disease, polyangiitis with granulomatosis, TB, and rheumatoid arthritis. Treatments · Steroid drops or ointments. · Cyclogyl dilating drops. · Steroid injections. · Steroid pills. · Non-steroidal anti-inflammatory pills. · Disease modifying anti-rheumatic drugs. Prognoses vary wildly depending on what type of anterior uveitis is found. In most cases, early treatment can prevent any possible effects on vision long-term. If the uveitis is recurrent or chronic in nature, if it is due to an auto-immune condition, or if it is due to an infection, even with proper treatment, can lead to cataract formation, opacifying cornea, swelling of the retina (macula) or even permanent vision loss. The chances of these outcomes dramatically declines with routine eye examinations and proper treatment.

Dr Ben Wild The conjunctiva is a clear layer of tissue that extends from the edge of the cornea, around the visible portion of the eye in front of the white sclera, and even the back surface of the eyelids. It posses as a barrier against foreign material and contributes to proper lubrication and tears. Frontal view of a healthy eye. Conjunctivitis, commonly referred to as “pink eye”, represents inflammation of the conjunctiva caused by either bacterial, chlamydial, and/or viral infections, allergies or others causes. Bacterial conjunctivitis occurs after contact with bacteria via other eyes or genitals. It begins unilaterally (in one eye) but transmission to the fellow eye 1-2 days later is common. Chlamydial conjunctivitis can spread eye to eye but often is spread via the genitals. It can be unilateral or bilateral and tends to take months to resolve unless properly treated. Viral conjunctivitis is most often caused by adenoviruses (90% of the time) or herpes simplex type 1 (HSV) aka the cold sore virus. It can range from mild to severe, starts unilaterally (in one eye) then becomes bilateral (both eyes) but is almost exclusively unilateral with HSV, and is often accompanied by a fever and sore throat. HSV often presents alongside skin vesicles on the eyelid. Other viruses include mumps, measles, shingles, HIV, COVID, etc. Allergic conjunctivitis is common and occurs after or during exposure to an allergen. Severe forms of allergic conjunctivitis include atopic and vernal keratoconjunctivitis. Atopic tends to develop in adulthood, symptoms tend to be more severe and is associated with eczema and asthma whereas vernal tends to affect primarily young boys and can resolve. Frontal view of an eye with severe conjunctivitis. Signs Common to all: eye redness Symptoms Common to all: tearing, grittiness, stinging, burning, light sensitivity Causes Infection of the conjunctiva. Risk Factors Exposure to bacteria, chlamydia, viruses or allergens, immunosuppressant use, any ocular trauma. Prevention Hygiene including washing the eyelids everyday and washing hands throughout the day. Treatments Common with all conjunctivitis: discontinue contact lens wear, reduce transmission risk by washing hands often and all pillow cases, towels, etc. that contact the face. Conjunctivitis is usually easily managed by the treatments listed above. However, it can leave permanent scarring to the eye which can be vision threatening if not treated. It can also be easily transmissible. Protecting others by decreasing transmission risk is essential.

Dr Ben Wild The cornea is a clear tissue located infront of the iris. Its main functions are as a barrier to protect the inner eye and to focus light on the retina. It is composed of 5 layers. The 3 main layers include the epithelium (outermost barrier layer), the stroma (the middle layer providing the refractive power), and the endothelium (responsible for pumping fluid out of the stroma so that the cornea does not swell and cloud over). Frontal view of a healthy eye. Herpes simplex virus (HSV) is a virus that can affect every part of the eye but usually only presents in the cornea. It accounts for 60% of all corneal ulcers and is the leading cause of corneal blindness in developed countries. There are 2 strains of the HSV. 1 is commonly referred to as the cold sore virus and stays above the waist, 2 is genital in origin but can affect the eyes through direct contact. Primary infection, meaning the first time a patient is infected by HSV, usually does not produce any symptoms or may present as a mild fever, upper respiratory tract infection, or mild conjunctivitis. It is transmitted via droplets. The virus DNA then incorporates into the patient’s DNA and becomes dormant. Usually within the trigeminal nerve. Recurrent infection occurs when the dormant virus DNA re-activates. This usually occurs due to various life stressors and is what causes damage to the eye in the form of epithelial keratitis (swollen epithelial cells of the cornea that can lead to ulceration), disciform keratitis (swollen endothelial cells caused by an intense immune reaction to the virus that leads to a swollen cornea), stromal keratitis (advanced form of disciform keratitis that can lead to the cornea melting), neurotrophic keratopathy (where the eye becomes numb, loses touch sensation and cannot heal), and more. An eye showing a dendritic corneal ulcer (the branching lesion) and disciform keratitis (circular area) from an HSV infection. Signs Symptoms Causes Re-activation of HSV in the trigeminal nerve. Risk Factors Fever, hormonal changes, ultra-violet radiation, eye surgeries, atopic allergies, immune-suppression, malnutrition, other viral infections, topical steroid use. Prevention Avoiding infection would be the best prevention but it is not practical as roughly 90% of the world’s population is estimated to have been infected by HSV1 or HSV2. Treatments · Topical acyclovir or trifluridine eye drops. · Oral acyclovir, valacyclovir or famciclovir pills. · Cyclogyl dilating drops for discomfort. · Topical antibiotic to avoid superinfection with bacteria. · Debride ulcer (remove infected epithelial). · Steroid eye drops if not epithelial keratitis. · Rigid gas permeable lenses to improve vision through scarring. · Keratoplasty (cornea transplant) if there is permanent scarring but this comes with a high rejection rate. Herpes simplex keratitis infections are typically recurrent, just like cold sores, and most often only affect the epithelium. These infections are easy to treat and do not usually cause much scarring or vision loss unless they are not treated in a timely manner. Each episode needs to be treated promptly. In order of treatment difficulty; disciform, neurotrophic and stromal keratitis’ are much less common. They can lead to permanent vision loss although that likelihood decreases dramatically with prompt treatment.

Dr Ben Wild The cornea is a clear tissue located infront of the iris. Its main functions are as a barrier to protect the inner eye and to focus light on the retina. It is composed of 5 layers. The 3 main layers include the epithelium (outermost barrier layer), the stroma (the middle layer providing the refractive power), and the endothelium (responsible for pumping fluid out of the stroma so that the cornea does not swell and cloud over). Frontal view of a healthy eye. Bacterial keratitis occurs when bacteria is able to adhere and colonize the cornea. This usually only occurs when the cornea is damaged because the corneal epithelium acts as a strong barrier, the tears contain active antimicrobial elements, and blinking flushes away any pathogens. There are, however, a few bacteria that can infect a healthy cornea. These bacteria include Neisseria gonorrhea, meningitidis, and Haemophilus influenza. Bacteria are typically classified as gram-positive or gram-negative depending on whether they have a secondary outer layer or not. Pseudomonas aeruginosa is the most common gram-negative bacteria and accounts for over 60% of contact lens related keratitis. It usually comes from touching the eye with your finger or another part of the body. Staphylococcus aureus is the most common gram-positive bacteria and usually stems from an overgrowth of bacteria on the eyelids. An eye showing a large bacterial colony and corneal infiltrate caused by bacterial keratitis. Signs White spot on the cornea representing white blood cells and bacteria, epithelial damage above the affected area, corneal swelling, uveitis, swollen eye, thinning or ulceration of the cornea, can lead to scarring endophthalmitis and scleritis. Symptoms Moderate to intense pain, light sensitivity, blurred vision, mucopurulent or purulent discharge (green to off white gooey discharge). Note: symptoms depend on type of bacteria and severity of infection. Causes Bacteria colonizing the cornea. Risk Factors Contact lens wear, sleeping in contact lenses (increases chances of infection by 20x!), trauma to the eye, eye surgery, ocular surface disease like dry eye, blepharitis, trichiasis, exposure, etc., immunosuppression, diabetes, vitamin A deficiency. Prevention Treat dry eyes, avoid contact lens over-use, avoid risk factors. Treatments Most bacterial keratitis’ resolve with a permanent scar. If this scar is not in the middle of the cornea, which it usually is not, vision should not be affected. Early detection and treatment greatly increases the likelihood that there will be a full recovery. A corneal transplant can restore vision in extreme cases.

Dr Ben Wild 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. These ganglion cells bunch together and form the optic nerve. The optic nerve then sends the signal to the occipital lobe in the brain where vision is interpreted and recognized. An image of a healthy retina and optic nerve. Occasionally, one (85% of cases) or both (15% of cases) optic nerves do not develop properly at birth. These poorly grown nerves tend to be much larger in size but have a large hole in the middle. Optic pits do not usually affect the development of vision in any way but can lead to central retinal detachments from fluid entering the hole and seeping underneath the retina. It can also lead to glaucoma-like blind spots with age. Retinal detachments due to optic disk pits occur by the age of 30 fifty percent of the time. An image of a healthy retina and an optic nerve disk pit. Signs Gray hole in the optic nerve. Symptoms None until a retinal detachment occurs (painless central vision loss). Causes Congenital anomaly (born with this condition). Risk Factors No known risk factors. Prevention There are no known preventative measures. Treatments · Use an AMSLER grid daily to monitor for metamorphopsia (distorted central vision). · Laser photocoagulation to create scar tissue between the retina and nerve so that a retinal detachment cannot occur. · Vitrectomy surgery to remove the vitreous gel inside the eye to eliminate the “pulling force” and lower the likelihood of a retinal detachment. Prognoses vary wildly depending on the location and size of the optic nerve pit. Small pits usually do not lead to any defects whereas large pits that lead to retinal detachment usually progress to a state of blindness without treatment. Surgical intervention before retinal detachment has greatly lowered the likelihood of retinal detachment.