The Cornea and Ocular Surface
The cornea is the clear outer dome of the eye that allows light to enter and become focused through the lens onto the retina. The cornea is an avascular tissue and receives most of its nutrients from the tears, the air and fluid inside the eye. Contact lens wear can starve the cornea of oxygen and lead to corneal neovascularization (blood vessel growth), infections, and scarring. It is important to be seen by your eye doctor as soon as you suspect anything out of the ordinary with your eyes.
The ocular surface includes the outer layer of the cornea, the tears, the conjunctiva, and the margin of the eye lids. This part of the eye has the most frequent injuries and ocular disease manifestations due to direct exposure to the environment. Please refer to the videos for a description of common conditions and procedures concerning the cornea and ocular surface.
Video on the Cornea and Ocular Surface
Common Cornea and Ocular Surface Conditions
Conjunctivitis is an inflammation of the conjunctiva, the thin, transparent layer that lines the inner eyelid and covers the white part of the eye. The three main types of conjunctivitis are infectious, allergic and chemical. Common symptoms of conjunctivitis are red watery eyes, inflamed inner eyelids, blurred vision, a scratchy feeling in the eyes, and sometimes a puslike or watery discharge.
To control the spread of infectious conjunctivitis, you should keep your hands away from your eyes, thoroughly wash your hands before applying eye medications and do not share towels, washcloths, cosmetics or eye drops with others.
Infection of the cornea and ocular surface are common and can be from several factors. Infection is often from contact lens wear, injury, or from another infected individual. Infections can be caused by many pathogens including bacteria, viruses, fungi, and protozoa. Proper contact lens wear is paramount to reduce the risk of infection. If these infections are not treated early there can be serious consequences including permanent scarring and vision loss. Medical and surgical treatments are available to reduce permanent damage and vision loss from infections.
Corneal dystrophies are a large group of disorders that often have a genetic component to their presentation. Many affect a specific layer of the cornea and result in an opacification or loss of clarity such as Fuch’s Endothelial Dystrophy. Others affect the shape and structure of the cornea such as Keratoconus.
In Keratoconus the corneal tissue is weakened and progressively thins and steepens which can distort vision even with glasses. Often specialty contact lenses are needed to see clearly and in severe cases corneal transplantation is required to obtain better vision. There are new treatments which show promise in stabilizing this progression without the need for corneal transplantation surgery in the less severe presentations of this disorder.
Fuch’s Endothelial Dystrophy
Fuch’s Endothelial Dystrophy affects the cornea’s ability to maintain a proper level of fluid internally. This causes swelling of the cornea which can damage the corneal tissue and lead to vision loss. This dystrophy is caused by a loss of function of the inner layer of the cornea called the endothelium. It is now possible to improve this dystrophy with a transplantation of just the inner layers of the cornea in a procedure called Descemet’s Stripping Endothelial Keratoplasty or DSEK.
Dry Eye Syndrome
Dry eye syndrome is the most common ocular condition. Common signs of dry eyes include redness, burning/gritty sensation, sharp eye pain, and transient blurred vision. There are several forms of dry eye caused by different factors. These range from a lack of adequate tear production, inadequate balance of normal tear components, incomplete blinking and lid closure, and more severe causes from autoimmune conditions.
It is important to see your eye doctor if you suspect you have dry eyes so they can properly diagnose the specific form of dry eye syndrome and treat it accordingly. There are now many palliative and medical treatments available to treat signs and symptoms of dry eye syndrome.
Pingueculae are benign raised yellowish lesions that form on the sclera (white) of the eye. They are more often nasal than temporal. They are usually found in the areas of the eye that receive sun exposure. These are common in sunny climates, especially in those individuals that do not wear sunglasses outdoors. Rarely do these cause symptoms other than cosmetic concerns, but they can cause dryness and become inflamed leading to a condition known as pingueculitis. Typically treatment is in the form of sun protection and artificial tears, but often with pingueculitis, steroid or NSAID eye drops are prescribed.
Pterygia are often thought to be an advanced form of pinguecula. They are benign triangular-shaped growths of fibrovascular tissue that grow from the sclera (white) of the eye onto the surface of the cornea. Pterygia are often more concerning cosmetically than pingueculae because they are more prominently located near the front of the eye. Large pterygia can grow into the line of sight and induce astigmatism leading to visual distortion and may require surgical excision. Unfortunately a large number of pterygia tend to recur and surgeons often employ antimetabolite agents or tissue grafts to reduce this re-growth.
Similar to the cause of pingueculae, significant exposure to the sun is thought to play a role in the growth of pterygia.