Corneal ulcers are most commonly due to infection, which may involve bacteria, viruses, fungi, or amoebas.
Non-infectious causes - all of which may be complicated by infection - include neurotrophic keratitis (resulting from loss of corneal sensation), exposure keratitis (due to inadequate eyelid closure), severe dry eyes, severe allergic eye disease, and various inflammatory disorders that may be purely ocular or part of a systemicvasculitis (inflammation).
Delayed or ineffective treatment of corneal infections may lead to devastating consequences through intraocular infection or corneal scarring. Prompt effective treatment is essential, so patients should see an ophthalmologist immediately.
A staphylococcal, Pseudomonas, or pneumococcal infection after trauma, complicating a corneal foreign body, or resulting from contact lens overwear is the usual primary cause of corneal ulcers.
Corneal ulcers also occur as complications of herpes simplex keratitis, chronicblepharitis, conjunctivitis (especially bacterial), trachoma, gonorrhea, and acute infectious diseases. Indolent ulcers are considered to be fungal until proved otherwise.
Corneal ulcers may also result from disturbances in corneal nutrition secondary to vitamin A or protein malnutrition, or from corneal exposure due to eyelid injuries or defective closure of the lids (lagophthalmos).
Typically, corneal ulceration begins with pain (aggravated by blinking), followed by increased tearing.
Eventually, central corneal ulceration produces pronounced visual blurring. The eye may appear infected. Purulent discharge is possible with a bacterial ulcer.
A hypopyon (accumulation of white cells or pus in the anterior chamber) may produce cloudiness or color change.
Diagnosis includes a patient history that may indicate trauma and flashlight examination that reveals an irregular corneal surface suggesting a corneal ulcer.
Fluorescein dye, instilled in the conjunctival sac, stains the outline of the ulcer and confirms the diagnosis. Culture and sensitivity testing of corneal scraping may identify the causative bacteria or fungus and indicate appropriate antibiotic or antifungal therapy.
Prompt treatment is essential for all forms of corneal ulcer to prevent complications and permanent visual impairment. Usually, treatment consists of systemic and topical broad-spectrum antibiotics until culture results identify the causative organism. The goals of treatment are to eliminate the underlying cause of the ulcer and to relieve pain.
In infection by Pseudomonas aeruginosa, polymyxin B and gentamicin are administered topically and by subconjunctival injection, or carbenicillin and tobramycin are administered I.V. Because this type of corneal ulcer spreads so rapidly, it can cause corneal perforation and loss of eye within 48 hours. Immediate treatment and isolation of hospitalized patients are required.
In infections by herpes simplex type 1 virus, idoxuridine or vidarabine is applied topically every hour. Corneal ulcers resulting from viral infection often recur; in this case, trifluridine becomes the treatment of choice.
In infection by varicella-zoster virus, topical sulfonamide ointment is applied three or four times daily to prevent secondary infection.
In infection by fungi, treatment is topical instillation of natamycin for Fusarium, Cephalosporium, and Candida.