WHAT IS THE CORNEA?
The cornea is the clear outer layer of the eye, creating a window which functions to focus and transmit light onto the retina. The cornea itself has five layers and is about half a millimeter thick. The cornea is extremely sensitive, having more nerve endings than anywhere else in the body.
Common Conditions & Treatment
The following is a list of some of the most common corneal conditions and diseases provided for your education by the National Eye Institute.
Preventing corneal disease starts with a healthy lifestyle. Eat a balanced plant-based diet and avoid refined, fatty, and sugary foods. Always avoid smoking and consuming alcohol. Exercise regularly, drink plenty of water, and get adequate sleep. More and more research is proving that a healthy lifestyle will lead to a healthy pair of eyes – visit our Health & Wellness blog for more information!
CONJUNCTIVITIS (Pink Eye)
This disease causes swelling, itching, burning, and redness of the conjunctiva, the protective membrane that lines the eyelids and covers exposed areas of the sclera, or white of the eye. Conjunctivitis is easily spread from person to person. Conjunctivitis can be caused by a bacterial or viral infection, allergy, environmental irritants, contact lens products, eye drops, or eye ointments. At its onset, conjunctivitis is usually painless and does not harm vision. The infection will clear in most cases without requiring medical care. But for some forms of conjunctivitis, treatment will be needed. If treatment is delayed, the infection may worsen and cause corneal inflammation and loss of vision.
Sometimes the cornea is damaged after a foreign object has entered the tissue, such as from a poke in the eye. At other times, bacteria or fungi from a contaminated contact lens can pass onto the cornea. Situations like these can cause painful inflammation and corneal infections called keratitis. These infections can reduce visual clarity, produce corneal discharges, and perhaps erode the cornea. Corneal infections can also lead to corneal scarring, which can impair vision and may require a corneal transplant.
As a general rule, the deeper the corneal infection, the more severe the symptoms and complications. It should be noted that corneal infections, although relatively infrequent, are the most serious complication of contact lens wear. Minor corneal infections are commonly treated with antibacterial eye drops. If the problem is severe, it may require more intensive antibiotic or anti-fungal treatment to eliminate the infection, as well as steroid eye drops to reduce inflammation. Frequent visits to an eye care professional may be necessary for several months to eliminate the problem.
The main symptom of dry eye is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon.
Dry eye is caused by an imbalance in the tear film that functions as the lubricant on the outside of our eyes.
Artificial tears, which lubricate the eye, are the principal treatment for dry eye. They are available over-the-counter as eye drops. Sterile ointments are sometimes used at night to help prevent the eye from drying. Using humidifiers, wearing wrap-around glasses when outside, and avoiding outside windy and dry conditions may bring relief.
Fuch’s dystrophy is a slowly progressing disease that usually affects both eyes. Fuchs’ dystrophy occurs when endothelial cells gradually deteriorate. As more endothelial cells are lost over the years, the endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision. Eventually, the epithelium also takes on water, resulting in pain and severe visual impairment.
Epithelial swelling damages vision by changing the cornea’s normal curvature, and causing a sight-impairing haze to appear in the tissue. Epithelial swelling will also produce tiny blisters on the corneal surface. When these blisters burst, they are extremely painful.
As the disease worsens, this swelling will remain constant and reduce vision throughout the day.
When the disease interferes with daily activity, a person may need to consider a corneal transplant. Lifestyle Eye Center most commonly performs the latest corneal transplant procedure: Descemet’s membrane endothelial keratoplasty (DMEK).
A corneal dystrophy is a condition in which one or more parts of the cornea lose their normal clarity due to a buildup of cloudy material. There are over 20 corneal dystrophies that affect all parts of the cornea.
Corneal dystrophies affect vision in widely differing ways. Some cause severe visual impairment, while a few cause no vision problems and are discovered during a routine eye examination. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision.
Some of the most common corneal dystrophies include Fuchs’ dystrophy, keratoconus, lattice dystrophy, and map-dot-fingerprint dystrophy.
This disorder–a progressive thinning of the cornea–is the most common corneal dystrophy in the U.S., affecting one in every 2,000 Americans. It is more prevalent in teenagers and adults in their 20’s. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape. This abnormal curvature changes the cornea’s refractive power, producing moderate to severe distortion (astigmatism) and blurriness (nearsightedness) of vision. Keratoconus may also cause swelling and a sight-impairing scarring of the tissue. Studies indicate that Keratoconus stems from one of several possible causes:
1. An inherited corneal abnormality.
2. An eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years.
3. Certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity, and vernal keratoconjunctivitis.
4. Systemic diseases, such as Leber’s congenital amaurosis, Ehlers-Danlos syndrome, Down syndrome, and osteogenesis imperfecta.
At first, people can correct their vision with eyeglasses. But as the astigmatism worsens, they must rely on specially fitted contact lenses to reduce the distortion and provide better vision.
Although finding a comfortable contact lens can be an extremely frustrating and difficult process, it is crucial because a poorly fitting lens could further damage the cornea and make wearing a contact lens intolerable.
In most cases, the cornea will stabilize after a few years without ever causing severe vision problems. But in about 10 to 20 percent of people with Keratoconus, the cornea will eventually become too scarred or will not tolerate a contact lens. If either of these problems occur, a corneal transplant may be needed.
A pterygium is a pinkish, triangular-shaped tissue growth on the cornea. Some pterygia grow slowly throughout a person’s life, while others stop growing after a certain point. A pterygium rarely grows so large that it begins to cover the pupil of the eye. Pterygia are more common in sunny climates and in the 20-40 age group. Scientists do not know what causes pterygia to develop. However, since people who have pterygia usually have spent a significant time outdoors, many doctors believe ultraviolet (UV) light from the sun may be a factor.
Because a pterygium is visible, many people want to have it removed for cosmetic reasons. It is usually not too noticeable unless it becomes red and swollen from dust or air pollutants. Lubricants can reduce the redness and provide relief from the chronic irritation.
About 120 million people in the United States wear eyeglasses or contact lenses to correct nearsightedness, farsightedness, or astigmatism. These vision disorders–called refractive errors– affect the cornea and are the most common of all vision problems in this country. Although eyeglasses or contact lenses are safe and effective methods for treating refractive errors, refractive surgeries are becoming an increasingly popular option.