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Corneal Disease

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What is the cornea?

The cornea is the clear tissue at the front and center of the eye. Its transparency permits light to pass into the eye, through the pupil, lens, and onto the retina at the back of the eye. The three major corneal layers are the outer layer of the cornea or epithelial layer, the middle layer termed the stroma, and finally a single layer of cells called the endothelium.

The curvature of the cornea plays an important role in focusing (refracting or bending) light. The normal cornea is smooth, clear, and tough. It helps protect the eye from infection and foreign material.

What are the different types of corneal disease?

There are several common causes of corneal disease, including the following:

  • Infections
    • Bacterial, fungal, or viral keratitis, as well as parasitic diseases
  • Trauma
    • Abrasions or exposure to toxic chemicals
  • Dystrophies and degenerative corneal disorders
  • Autoimmune disorders
  • Nutritional deficiencies
    • Vitamin A deficiency
  • Allergies
    • Vernal and atopic keratoconjunctivitis
  • Growths
    • Pterygium or benign or malignant cancerous growths on the eye's surface
  • Ectasia (thinning)
    • Keratoconus, or thinning of the cornea following refractive laser surgery
  • Stevens-Johnson syndrome, a rare but serious inflammatory reaction to a medication or an infection

The cornea can also be damaged secondarily by other common eye conditions such as tear film abnormalities (dry eye), eyelid disorders, glaucoma, and iridocorneal endothelial syndrome (ICE), which may be associated with glaucoma.

Medically Reviewed by a Doctor on 2/14/2017


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