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Corneal ulcers have many causes (see table Causes of Corneal Ulcers). Herpes simplex keratitis is discussed separately.

Bacterial ulcers are most commonly due to contact lens wear and are rarely due to secondary infection from traumatic abrasion or herpes simplex keratitis. The response to the treatment depends mostly on the bacterial species, and the ulcer may be particularly refractory to treatment.

The time course for ulcers varies. Ulcers caused by Acanthamoeba (most commonly due to exposure to contaminated water while wearing contact lenses) and fungi (most commonly due to trauma with vegetable material) are indolent but progressive, whereas those caused by Pseudomonas aeruginosa (seen most frequently in contact lens wearers) develop rapidly, causing deep and extensive corneal necrosis. Wearing contact lenses while sleeping or wearing inadequately disinfected contact lenses can cause corneal ulcers (see Contact Lenses: Care and Complications).

Ulcers are characterized by corneal epithelial defects with an underlying inflammatory infiltrate, along with inflammation and sometimes necrosis of the corneal stroma. Corneal ulcers tend to heal with scar tissue, resulting in opacification of the cornea and decreased visual acuity. Uveitis, corneal perforation with iris prolapse, pus in the anterior chamber (hypopyon), panophthalmitis, and destruction of the eye may occur without treatment and, on occasion, even with the best available treatment, particularly if treatment is delayed. More severe symptoms and complications tend to occur with deeper ulcers.

Conjunctival redness, eye ache, foreign body sensation, photophobia, and lacrimation may be minimal initially.

A corneal ulcer begins as a corneal epithelial defect that stains with fluorescein and an underlying dull, grayish, circumscribed opacity (representing an infiltrate). Subsequently, the ulcer suppurates and necroses to form an excavated ulcer. Considerable circumcorneal conjunctival hyperemia is usual. More severe ulcers may spread to involve the width of the cornea, may penetrate deeply, or both. Also, in these cases, a hypopyon (layered white blood cells [WBCs] in the anterior chamber) may occur. In long-standing cases, blood vessels may grow in from the limbus (corneal neovascularization).

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Corneal ulcers due to Acanthamoeba are often intensely painful and may show transient corneal epithelial defects, multiple corneal stromal infiltrates, and, later, a large ring-shaped infiltrate. Fungal ulcers, which are more chronic than bacterial ulcers, are densely infiltrated and may show occasional multiple discrete islands of infiltrate (satellite lesions) at the periphery. Dendritic ulcers are characteristic of herpes simplex keratitis.

• Slit-lamp examination

Diagnosis is made by slit-lamp examination; a corneal infiltrate with an overlying epithelial defect that stains with fluorescein is diagnostic. All but small ulcers should be cultured by scraping with a disposable #15 blade, sterile platinum spatula, or jeweler's forceps (typically by an ophthalmologist). Microscopic examination of scrapings can be used to identify Acanthamoeba.

• Initially empiric topical broad-spectrum antibiotic therapy

• More specific antimicrobial therapy directed at the cause

Treatment for corneal ulcers can involve antimicrobials, cycloplegics, and occasionally corticosteroids (1). Treatment for all ulcers, regardless of cause, begins with moxifloxacin 0.5% or gatifloxacin 0.3 to 0.5% eye drops for small ulcers and fortified (higher than stock concentration) antibiotic drops, such as tobramycin 15 mg/mL and cefazolin 50 mg/mL, for more significant ulcers, particularly those that are near or involve the center of the cornea. Frequent dosing (eg, every 15 minutes for 4 doses, followed by every hour around the clock) is necessary initially. Patching is contraindicated because it creates a stagnant, warm environment that favors bacterial growth and prevents the administration of topical medications.

Herpes simplex is treated with trifluridine or ganciclovir gel. Eye drops are preferred, but if patients cannot administer drops reliably or drops are not available, oral medications such as valacyclovir or acyclovir can be used.

Fungal infections are treated with topical antifungal drops, such as natamycin (the medication of choice for filamentous fungus, eg, Fusarium), amphotericin B (the medication of choice for yeast, eg, Candida), or sometimes voriconazole (which is less effective but has the broadest spectrum). Deep infections may require addition of oral voriconazole, ketoconazole, fluconazole, or itraconazole.

If Acanthamoeba is identified, therapy can include topical propamidine, neomycin, and polyhexamethylene biguanide or chlorhexidine supplemented with miconazole, clotrimazole, or oral ketoconazole or itraconazole. The drops are used frequently until clinical improvement is evident, then gradually tapered and continued for a number of months until all inflammation has resolved. Polyhexamethylene biguanide and chlorhexidine are not commercially available as ocular agents but can be prepared by a compounding pharmacy. Oral miltefosine can be used for recalcitrant cases.

For all ulcers, treatment may also include a cycloplegic, such as atropine 1% or scopolamine 0.25% 1 drop 3 times/day, to decrease the ache of a corneal ulcer and to reduce the formation of posterior synechiae. In severe cases, debridement of the infected epithelium or even penetrating keratoplasty may be required. Patients who may have difficulty administering eye drops at home or who have large, central, or refractory ulcers may need to be hospitalized.

Very selectively, patients can be treated adjunctively with a corticosteroid drop (eg, prednisolone acetate). The final appearance of the scar and final visual acuity may not improve with topical corticosteroids. Topical corticosteroids do decrease the pain and photophobia, and speed the increase in visual acuity, significantly. Because there is a very small risk of the ulcer worsening, adding topical corticosteroids is only indicated when a patient needs to get back to normal functioning (eg, work, driving) as soon as possible. Of note, topical corticosteroids are contraindicated if HSV keratitis is suspected or diagnosed. Such treatment should only be prescribed by ophthalmologists and should be restricted to patients in whom clinical and microbiologic evidence indicates a favorable response to antimicrobial treatment and who can be closely followed.