Introduction to Keratitis

Keratitis, also known as inflammation of the cornea, may be acute or chronic, superficial or deep. Superficial keratitis is fairly common and may develop at any age. The prognosis is good with treatment. Untreated, recurrent keratitis may lead to blindness.

Causes
Keratitis may result from exposure (as in Bell’s palsy where the eyelids don’t close), wearing contact lenses for prolonged periods (overnight), or corneal trauma. It may also result from infection by herpes simplex virus, type 1 (known as dendritic keratitis because of a characteristic branched lesion of the cornea resembling the veins of a leaf). Less commonly, it stems from bacterial or fungal infection; rarely, from congenital syphilis.

Signs and symptoms
Unilateral keratitis may produce pain, tearing, and photophobia. If the infection is in the center of the cornea, it may produce blurred vision. Left untreated, corneal opacities can occur. When keratitis results from exposure, it usually affects the lower portion of the cornea.

Diagnosis
A slit-lamp examination reveals the depth of the keratitis. If it’s due to herpes simplex virus, staining the eye with a fluorescein strip produces one or more small branchlike (dendritic) lesions; touching the cornea with cotton reveals reduced corneal sensation. Vision testing may show slightly decreased acuity. The patient history may reveal a recent infection of the upper respiratory tract accompanied by cold sores.

Treatment
With acute keratitis due to herpes simplex virus, treatment consists of trifluridine eyedrops or vidarabine ointment. A broad-spectrum antibiotic may prevent secondary bacterial infection.
Chronic dendritic keratitis may respond more quickly to vidarabine. Long-term topical therapy may be necessary. (Corticosteroid therapy is contraindicated in patients with dendritic keratitis or another viral or fungal disease of the cornea.) Treatment of fungal keratitis involves natamycin.
Keratitis due to exposure requires application of moisturizing ointment to the exposed cornea and of a plastic bubble eye shield or eye patch. Treatment of severe corneal scarring may include keratoplasty (cornea transplantation).

Special considerations
Look for keratitis in the patient predisposed to cold sores. Explain that stress, trauma, fever, colds, and overexposure to the sun may trigger flare-ups.