(See also Introduction to Corneal Disorders Introduction to Corneal Disorders Symptoms that suggest corneal involvement (eg, rather than simple conjunctivitis) include unilateral involvement, pain (foreign body sensation and ache—not just a gritty sensation), particularly... read more .)
Etiology of Corneal Ulcer
Corneal ulcers have many causes (see table Causes of Corneal Ulcers Causes of Corneal Ulcers A corneal ulcer is a corneal epithelial defect with underlying inflammation usually due to invasion by bacteria, fungi, viruses, or Acanthamoeba. It can be initiated by mechanical trauma or... read more ). Herpes simplex keratitis Herpes Simplex Virus (HSV) Infections Herpes simplex viruses (human herpesviruses types 1 and 2) commonly cause recurrent infection affecting the skin, mouth, lips, eyes, and genitals. Common severe infections include encephalitis... read more 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 may be particularly refractory to treatment. The time course for ulcers varies. Ulcers caused by Acanthamoeba (also 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 Care and Complications Contact lenses provide better peripheral vision than do eyeglasses and can be prescribed to correct the following: Myopia Hyperopia Astigmatism Anisometropia read more ).
Pathophysiology of Corneal Ulcer
Ulcers are characterized by corneal epithelial defects with underlying inflammation and necrosis of the corneal stroma. Corneal ulcers tend to heal with scar tissue, resulting in opacification of the cornea and decreased visual acuity. Uveitis Overview of Uveitis Uveitis is defined as inflammation of the uveal tract—the iris, ciliary body, and choroid. However, the retina and fluid within the anterior chamber and vitreous are often involved as well.... read more , 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.
Symptoms and Signs of Corneal Ulcer
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 superficial 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).
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 show occasional multiple discrete islands of infiltrate (satellite lesions) at the periphery. Dendritic ulcers are characteristic of herpes simplex keratitis Herpes Simplex Keratitis Herpes simplex keratitis is corneal infection with herpes simplex virus. It may involve the iris. Symptoms and signs include foreign body sensation, lacrimation, photophobia, and conjunctival... read more .
Diagnosis of Corneal Ulcer
Diagnosis is made by slit-lamp examination Slit-lamp examination The eye can be examined with routine equipment, including a standard ophthalmoscope; thorough examination requires special equipment and evaluation by an ophthalmologist. History includes location... read more ; 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 identify Acanthamoeba.
Treatment of Corneal Ulcer
Initially empiric topical broad-spectrum antibiotic therapy
More specific antimicrobial therapy directed at the cause
Treatment for corneal ulcers, regardless of cause, begins with moxifloxacin 0.5% or gatifloxacin 0.3 to 0.5% 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 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 drugs.
Herpes simplex Herpes Simplex Keratitis Herpes simplex keratitis is corneal infection with herpes simplex virus. It may involve the iris. Symptoms and signs include foreign body sensation, lacrimation, photophobia, and conjunctival... read more is treated with trifluridine 1% drops every 2 hours while the patient is awake to a total of 9 times/day, ganciclovir 0.15% gel 5 times/day, valacyclovir 1000 mg orally twice a day, or acyclovir 400 mg orally 3 to 5 times/day (or 3 times/day for recurrent herpes simplex keratitis) for about 14 days.
Fungal infections are treated with topical antifungal drops (eg, natamycin 5%, amphotericin B 0.15%, and sometimes voriconazole 1% [which is less effective]), initially every hour during the day and every 2 hours overnight. Deep infections may require addition of oral voriconazole 400 mg twice/day for 2 doses then 200 mg twice/day, ketoconazole 400 mg once/day, fluconazole 400 mg once then 200 mg once/day, or itraconazole 400 mg once then 200 mg once/day.
If Acanthamoeba is identified, therapy can include topical propamidine 0.1%, neomycin 0.175%, and polyhexamethylene biguanide 0.02% or chlorhexidine 0.02% supplemented with miconazole 1%, clotrimazole 1%, or oral ketoconazole 400 mg once/day or itraconazole 400 mg once then 200 mg once/day. The drops are used every 1 to 2 hours until clinical improvement is evident, then gradually reduced to 4 times/day 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 are poorly compliant or who have large, central, or refractory ulcers may need to be hospitalized. Very selective patients can be treated adjunctively with a corticosteroid drop (eg, prednisolone acetate 1% four times/day for 1 week then tapered over 2 to 3 weeks). The final appearance of the scar and final visual acuity are not improved 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. 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.
Causes of corneal ulcers include infection of the cornea (including overwearing of contact lenses), eye trauma, abnormalities of the eyelid, and nutritional deficiencies.
Ulcers may be accompanied by circumcorneal hyperemia and WBC layering in the anterior chamber (hypopyon).
All but the smallest ulcers are cultured, usually by an ophthalmologist.
Treatment usually involves frequent (eg, every 1 to 2 hours around the clock) application of topical antimicrobials.