Corneal disease
The cornea is a clear, dome-shaped surface that covers the front of the eye. It has two main functions:
Protection – The cornea shields the rest of the eye from germs, dust, and other harmful objects. The cornea also serves as a filter for some of the most damaging ultraviolet (UV) wavelengths in sunlight.
Vision - The cornea focuses the entry of light into the eye. When light strikes the cornea, it bends (refracts)the incoming light onto the lens. The lens refocuses that light onto the retina, which then converts the light into electrical signals that it sends to the brain. The brain translates these signals into images.
Dry Eyes
In people with dry eyes, the eye produces fewer or lower quality tears and is unable to keep itself moist and comfortable. The main symptom of dry eye is a scratchy or sandy feeling as if something is in the eye. Other symptoms might include stinging or burning of the eye; periods of excess tearing that follow periods of dryness; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye feel heaviness in their eyelids or have vision problems.
Dry eye can be more likely in people who live in dry air, as well as those who use certain medications, including antihistamines, nasal decongestants, tranquilizers, and anti-depressants. People with dry eye should let their health care providers know all the medications they are taking, since some medications might make dry eye symptoms worse. Dry eye is also more common in women, especially after menopause.
People with connective tissue diseases, such as rheumatoid arthritis, can be prone to dry eye. Dry eye is sometimes a symptom of Sjögren's syndrome, a disease that attacks the body's lubricating glands, such as the tear and salivary glands. A complete physical examination can help diagnose any underlying diseases. An exam called a Schrimer's test might be used to measure tear production.
The main treatment for dry eye is artificial tears, which can moisten the eye. They are available over-the-counter as eye drops. 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 might help as well. For people with severe cases of dry eye, temporarily or permanently blocking the eyelid puncta (small openings at the inner corner of the eyelids where tears drain from the eye) with punctual plugs is another treatment option. A treatment called topical cyclosporine therapy (Restasis), might also be used to increase tear production. Most people who have this treatment need to use it continuously for at least three months before their tear production improves.
Corneal infections
Corneal infections – Damage to the cornea from injury or bacteria can cause painful inflammation and corneal infections. Another name for a corneal infection is keratitis. Corneal infections can be a rare but serious complication of contact lens wear. They can reduce clarity of vision, cause corneal discharges, and even erode the cornea. They can also lead to corneal scarring, which can harm vision and might require a corneal transplant.
Minor corneal infections are usually treated with anti-microbial eye drops. Severe infections might require stronger antibiotic or antifungal or antiviral treatments. It might be necessary to make frequent visits to an eye doctor for several months. Once the infection is under control, topical steroid treatments might be used to help with corneal scarring.
Pterygium
Pterygium - A pterygium is a pinkish, triangular-shaped growth of tissue on the cornea. Pterygia are more common in sunny climates and in people aged 20 to 40. 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.
Because a pterygium is easy to notice on the face, many people with the condition want to have it removed for cosmetic reasons. However, surgery to remove a pterygium is not recommended unless the pterygium affects vision or causes discomfort. If a pterygium is surgically removed, it might grow back, particularly if the person is younger than 40. There are many treatments eye doctors can use to make it less likely that the pterygium will grow back. These include the use of conjunctival autografts, amniotic membrane, and a medication called mitomycin-C.
The pterygium should not be very noticeable unless it becomes red and swollen from dust or air pollutants. Lubricants can reduce the redness and provide relief from the chronic irritation.
Scientists do not know what causes pterygia. However, people who have pterygia usually have spent a lot of time outdoors, and many doctors believe ultraviolet (UV) light from the sun might be a factor. In areas where sunlight is strong, it is important to wear protective eyeglasses, sunglasses, and/or hats with brims.
Ocular Herpes
Ocular herpes – This condition is caused by recurrent viral infections from the herpes simplex virus. It causes a painful sore on the eyelid or surface of the eye and inflammation of the cornea.
Prompt treatment with anti-viral medications can help stop the herpes virus from multiplying and destroying cells in the cornea.
Research has shown that once a person develops ocular herpes, he or she has up to a 50 percent chance of having a recurrence. The next flare-up could come weeks or even years after the last occurrence. Some factors believed to be associated with recurrence include fever, stress, sunlight, and eye injury.
In some cases, the infection spreads and becomes a more severe infection called stromal keratitis. This causes the body's immune system to attack and destroy cells in the stroma. Stromal keratitis is more difficult to treat than other ocular herpes infections. Repeated episodes of stromal keratitis can cause scarring of the cornea. This can lead to loss of vision and even blindness.
Herpes Zoster
Herpes zoster (shingles) is an infection that is caused by the varicella-zoster virus. This is the same virus that causes chickenpox. In most cases, once a person recovers from chickenpox, the virus remains inactive in his or her body. But in some people, the virus becomes active again later in life. When this happens, the virus travels down nerve fibers and can infect any part of the body. The infection causes a blistering rash (called shingles), fever, painful inflammations of the affected nerve fibers, and a general feeling of sluggishness. In many people who have a varicella-zoster infection in their head or neck, the virus also affects the cornea.
To treat an infection in the cornea, doctors will often prescribe oral anti-viral medication. This can lower the risk of inflammation and scarring in the cornea. The virus can also decrease corneal sensitivity. This means that the cornea will not be as sensitive to foreign objects, such as stray eyelashes. In many cases, this decreased sensitivity is permanent.
Corneal problems can happen arise after the virus is gone. For this reason, it is important that people who have had shingles on their face have regular follow-up eye examinations.
Keratoconus
Keratoconus is the most common corneal dystrophy, and is most prevalent in teenagers and adults in their 20s. It happens when the middle of the cornea thins and gradually bulges outward, forming a cone shape. This bulging changes the how the cornea refracts (bends) light, and can cause refractive errors such as nearsightedness and astigmatism. It can also cause swelling and scarring of the cornea, which can harm vision. Keratoconus usually affects both eyes.
At first, vision problems from keratoconus can be treated with eyeglasses. But as the astigmatism worsens, specially-fitted contact lenses might be needed to reduce the distortion and provide better vision. It is important that the contact lenses fit properly, because a poorly fitting lens can cause further damage the cornea. This might prevent the person from being able to wear contact lenses.
Another treatment, called cornal collagen crosslinking, has recently been shown to stop the progression of keratoconus.
However, not all people with keratoconus can be helped by these treatments. In about 10 to 20 percent of people with this condition, the cornea will become too scarred or will not tolerate a contact lens. If either of these problems happen, a corneal transplant might be necessary to treat the keratoconus.
Other Corneal Disorders
Corneal dystrophies are conditions in which one or more parts of the cornea lose their normal clarity due to a buildup of cloudy material. Many of them are inherited and not the result of other health or lifestyle factors.
Some cause severe vision problems, while a few cause no vision problems and are only noticed during a routine eye examination. Other dystrophies might cause severe pain without leading to permanent vision loss.
Limbal Stem Cell Deficiency is a condition that results from a failure in limbal stem cells to properly repair and regenerate the surface of the cornea. This can lead to thinning, painful ulceration, and opacity in the cornea, and eventually possible blindness.
Ocular cicatricial pemphigoid is caused by a rare systemic autoimmune disorder that primarily attacks the conjunctiva of the eye. The conjunctiva is the thin mucous membrane that covers the inner eyelid and sclera (white of the eye), important in lubricating and protecting the eye. When the conjunctiva is attacked, inflammation (conjunctivitis), infection, and scarring (cicatrization) results. If Ocular cicatricle pemphigoid progresses without treatment, it can lead to blindness.