Keratitis
Keratitis: Excerpt from Professional Guide to Diseases (Eighth Edition)
An inflammation of the cornea, keratitis may result from bacterial, fungal, or viral infection. If untreated, the infection can lead to blindness.
Causes
The most common cause of keratitis is infection by herpes simplex virus, type 1 (known as dendritic corneal ulcer because of a characteristic branched lesion of the cornea resembling the veins of a leaf). Bacterial corneal ulcers frequently occur as a result of an infected corneal abrasion or a contaminated contact lens. Fungal keratitis is more frequently encountered in tropical climates. Poor lid closure can result in exposure keratitis. Chemicals accidentally splashed into the eye and exposure to ultraviolet light (sunlamps, sunlight, or welding arcs) also can produce keratitis. Vaccinial keratitis may result when the patient has red eye or periocular vesicles coinciding with a history of recent vaccine exposure (such as smallpox vaccination or close contact with a vaccine recipient).
Signs and symptoms
Keratitis is usually unilateral. The patient presents with decreased vision, discomfort ranging from mild irritation to acute pain, tearing, and photophobia. On gross examination with a penlight, the corneal light reflex may appear distorted. When keratitis results from exposure, it usually affects the lower portion of the cornea.
Diagnosis
Confirming diagnosis Visual acuity may be decreased if the lesion is central. Slit-lamp examination confirms keratitis. Staining the eye with a sterile fluorescein strip enables the examiner to discern the extent and depth of the corneal lesion.
Patient history may reveal a recent infection of the upper respiratory tract accompanied by cold sores, or eye irritation with the wearing of contact lenses. Culture may identify the virus.
Treatment
Treatment for acute keratitis due to herpes simplex virus consists of trifluridine eyedrops, vidarabine ointment, or oral acyclovir. A broad-spectrum antibiotic may prevent secondary bacterial infection. Dendritic keratitis may become chronic with recurrent episodes. Bacterial corneal ulcers require intense topical eyedrop instillation every half hour for the first 48 hours with 2 broad-spectrum antibiotics. Long-term topical therapy may be necessary. (Corticosteroid therapy is contraindicated in dendritic keratitis or any other viral or fungal disease of the cornea.) Fungal keratitis is treated with natamycin.
Exposure keratitis is treated with ointment at night and frequent instillation of artificial tears during the day. A plastic bubble shield may prevent tear evaporation. Vision may be restored by penetrating keratoplasty (corneal transplant) in blindness resulting from corneal scarring.
Special considerations
❑ Protect the exposed corneas of unconscious patients by cleaning the eyes daily, applying moisturizing ointment, or covering the eyes with an eye shield.
❑ Be aware that the patient with a red eye may have keratitis. Check for a history of contact lens wear, cold sores, or recent foreign-body sensation. Refer the patient for slit-lamp examination as soon as possible for intense treatment.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Conjunctival injection (Professional Guide to Signs & Symptoms (Fifth Edition))
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