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Keratitis

Keratitis

What is it?
Keratitis is an inflammation of the cornea caused by infection, trauma, dry eyes, ultraviolet exposure, contact lens overwear, or degeneration.

Keratitis often begins with erosion of the epithelial surface. You can usually spot it by seeing that the light reflection in the affected region is hazy and broken up.

Fluorescein staining is a big help because it turns areas of damaged epithelium green. A cobalt blue filter enhances fluorescence.

Once the inflammation extends beneath the epithelium, the healing process will leave a scar that impairs sight.

A common cause of infectious keratitis is herpes simplex, which produces a tree-branch ("dendritic") shaped erosion. It must be treated promptly with topical (trifluorothymidine or adenine arabinoside) or oral (acyclovir, valacyclovir, famciclovir) anti-viral medications to prevent penetration into the deeper layers. Deep infection typically leads to corneal opacification or loss of tissue (ulceration). Then there is a threat of corneal perforation and infection inside the eye (endophthalmitis).

How does it present?
Symptoms of keratitis are blurred vision, photophobia, periocular pain, and foreign-body sensation. The conjunctival blood vessels are dilated most intensely around the edge of the cornea (ciliary flush, circumcorneal flush). But there may be surprisingly little redness. If white cells invade an infected cornea, you will see a white cloud instead of a transparent cornea.

What to do?
Do not attempt to treat. Refer emergently because of the complexity of diagnosis and the importance of specific treatment to prevent permanent loss of vision.

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