What is Cornea?

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The cornea is the eye's outermost layer. It is the clear, dome-shaped surface that covers the front of the eye.

What are Coroneal Diseases?

Some diseases and disorders of the cornea are:
1. Allergies. Allergies affecting the eye are fairly common. The most common allergies are those related to pollen, particularly when the weather is warm and dry. Symptoms can include redness, itching, tearing, burning, stinging, and watery discharge, although they are not usually severe enough to require medical attention.
2.Conjunctivitis (Pink Eye). This term describes a group of diseases that cause 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 can spread from one person to another and affects millions of Americans at any given time.
3. Corneal Infections. 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 into the cornea. Situations like these can cause painful inflammation and corneal infections called keratitis.
4. Dry Eye. The continuous production and drainage of tears is important to the eye's health. Tears keep the eye moist, help wounds heal, and protect against eye infection. In people with dry eye, the eye produces fewer or less quality tears and is unable to keep its surface lubricated and comfortable.
5. Fuchs' Dystrophy. Fuchs' dystrophy is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. Although doctors can often see early signs of Fuchs' dystrophy in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.
6. Corneal Dystrophies. 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. These diseases share many traits:

  • They are usually inherited.
  • They affect the right and left eyes equally.
  • They are not caused by outside factors, such as injury or diet.
  • Most progress gradually.
  • Most usually begin in one of the five corneal layers and may later spread to nearby layers.
  • Most do not affect other parts of the body, nor are they related to diseases affecting other parts of the eye or body.
  • Most can occur in otherwise totally healthy people, male or female.
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.
7. Herpes Zoster (Shingles). This infection is produced by the varicella-zoster virus, the same virus that causes chickenpox. After an initial outbreak of chickenpox (often during childhood), the virus remains inactive within the nerve cells of the central nervous system. But in some people, the varicella-zoster virus will reactivate at another time in their lives.
8. Iridocorneal Endothelial Syndrome. More common in women and usually diagnosed between ages 30-50, iridocorneal endothelial (ICE) syndrome has three main features: (1) visible changes in the iris, the colored part of the eye that regulates the amount of light entering the eye; (2) swelling of the cornea; and (3) the development of glaucoma, a disease that can cause severe vision loss when normal fluid inside the eye cannot drain properly. ICE is usually present in only one eye.
9. Keratoconus. 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 20s. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape.
10. Lattice Dystrophy. Lattice dystrophy gets its name from an accumulation of amyloid deposits, or abnormal protein fibers, throughout the middle and anterior stroma. During an eye examination, the doctor sees these deposits in the stroma as clear, comma-shaped overlapping dots and branching filaments, creating a lattice effect. Over time, the lattice lines will grow opaque and involve more of the stroma.
11. Map-Dot-Fingerprint Dystrophy. This dystrophy occurs when the epithelium's basement membrane develops abnormally (the basement membrane serves as the foundation on which the epithelial cells, which absorb nutrients from tears, anchor and organize themselves). When the basement membrane develops abnormally, the epithelial cells cannot properly adhere to it.
12. Ocular Herpes. Herpes of the eye, or ocular herpes, is a recurrent viral infection that is caused by the herpes simplex virus and is the most common infectious cause of corneal blindness in the U.S. Previous studies show that once people develop ocular herpes, they have up to a 50 percent chance of having a recurrence. This second flare-up could come weeks or even years after the initial occurrence.
13. Pterygium. 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.
14. Stevens-Johnson Syndrome. Stevens-Johnson Syndrome (SJS), also called erythema multiforme major, is a disorder of the skin that can also affect the eyes. SJS is characterized by painful, blistery lesions on the skin and the mucous membranes (the thin, moist tissues that line body cavities) of the mouth, throat, genital region, and eyelids.

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