Corneal ulcers
Corneal ulcers: Excerpt from Handbook of Diseases
A major cause of blindness worldwide, corneal ulcers produce corneal scarring or perforation. They occur in the central or marginal areas of the cornea, vary in shape and size, and may be singular or multiple. Marginal ulcers, caused by a sensitivity to Staphylococcus aureus, are the most common form. Prompt treatment (within hours of onset) can prevent visual impairment.
Causes
Corneal ulcers generally result from bacterial, protozoan, viral, or fungal infections. Common bacterial sources include Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus viridans, Streptococcus (Diplococcus) pneumoniae, and Moraxella liquefaciens; viral sources, herpes simplex type 1, and varicella-zoster viruses; and common fungi, such as Candida, Fusarium, and Cephalosporium.
Other causes include trauma, exposure, reactions to bacterial infections, toxins, and allergens. Tuberculoprotein causes a classic phlyctenular keratoconjunctivitis; vitamin A deficiency results in xerophthalmia; and fifth cranial nerve lesions result in neurotropic ulcers.
Signs and symptoms
Typically, corneal ulceration begins with pain (aggravated by blinking) and photophobia, followed by increased tearing. Eventually, central corneal ulceration produces pronounced visual blurring. The eye may appear injected (red). If a bacterial ulcer is present, purulent discharge is possible.
Diagnosis
A history of trauma or use of contact lenses and a flashlight examination that reveals an irregular corneal surface suggest corneal ulcer. Exudate may be present on the cornea, and a hypopyon (accumulation of white cells in the anterior chamber) may appear as a half-moon.
Fluorescein dye, instilled in the conjunctival sac, delineates the outline of the ulcer. Culture and sensitivity testing of corneal scrapings, which may identify the causative bacteria or fungus, indicate appropriate antibiotic or antifungal therapy.
Treatment
Prompt treatment is essential for all forms of corneal ulcer to prevent complications and permanent visual impairment. Treatment aims to eliminate the underlying cause of the ulcer and to relieve pain.
Until culture results identify the causative organism, treatment consists of topical broad-spectrum antibiotics. Once the causative agent is identified, specific treatments vary.
❑ P. aeruginosa infection is treated with ciprofloxacin, gentamicin, or tobramycin, administered topically. This type of corneal ulcer can cause corneal perforation and loss of the eye very rapidly if left untreated. Immediate treatment and isolation of hospitalized patients are required.
A corneal ulcer should never be patched because patching creates the dark, warm, moist environment ideal for bacterial growth. However, it should be protected with a perforated shield.
❑ Herpes simplex type 1 virus is treated with hourly topical applications of idoxuridine or vidarabine. Corneal ulcers resulting from this viral infection commonly recur. Trifluridine is the treatment of choice.
❑ Fungi are treated with topical instillation of natamycin for Fusarium, Cephalosporium, and Candida.
❑ Hypovitaminosis A requires correction of dietary deficiency or GI malabsorption of vitamin A.
❑ Neurotropic ulcers or exposure keratitis is treated with frequent instillation of artificial tears or lubricating ointments and use of a plastic bubble eye shield or by a tarsorrhaphy (suturing the eyelids together).
Special considerations
❑ Because corneal ulcers are quite painful, give analgesics as needed.
Clinical tip Because an associated iridocyclitis occurs when the cornea is involved, cycloplegic eyedrops are given to reduce ciliary body spasms.
❑ Watch for signs of secondary glaucoma (transient vision loss and halos around lights).
❑ The patient may be more comfortable in a darkened room or when wearing dark glasses.
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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