What is the pathophysiology of corneal ulcers?

Updated: Nov 08, 2018
  • Author: Jesse Borke, MD, FACEP, FAAEM; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

Although corneal ulcers may occasionally be sterile, most are infectious in etiology.

Bacterial keratitis is the most important etiology to exclude in the emergency department (ED). Corneal infections and infectious keratitis are often presumed to be bacterial until proven otherwise.

Bacterial corneal ulcers may follow a break in the corneal epithelium, thereby providing an entry for bacteria. The traumatic episode may be minor, such as a minute abrasion from a small foreign body, or may result from such causes as tear insufficiency, malnutrition, or contact lens use. Increased use of soft contact lenses in recent years has led to a dramatic rise in the occurrence of corneal ulcers, particularly due to Pseudomonas aeruginosa. [1]

Common bacterial isolates cultured from patients with keratitis include P aeruginosa, coagulase-negative staphylococci, Staphylococcus aureus, Streptococcus pneumoniae, and Enterobacteriaceae (including Klebsiella, Enterobacter, Serratia, and Proteus). Klebsiella pneumoniae mucoid phenotype and its ability to form biofilm may be important in producing corneal ulceration. Agents such as N-acetylcysteine, may have a role in treatment because they inhibit biofilm formation.

Ulcers due to viral infection occur on a previously intact corneal epithelium.

Herpes simplex and varicella-zoster viruses can both cause a significant infectious keratitis. [2]

With the introduction of topical corticosteroid drugs in the treatment of eye disease, fungal corneal ulcers have become more common. Fungi (Fusarium and Candida species) and parasitic amoeba (Acanthamoeba) have been found in a small number of patients and frequently present with more severe symptoms.

Peripheral ulcerative keratitis (PUK) is a complication of rheumatoid arthritis (RA) that can lead to rapid corneal destruction (corneal melt) and perforation with loss of vision. An example is shown in the image below.

Peripheral ulcerative keratitis in the right eye o Peripheral ulcerative keratitis in the right eye of a patient with rheumatoid arthritis. Glue has been placed.

Mooren ulcer is an idiopathic ulceration of the peripheral cornea that may result from an autoimmune reaction or may be associated with hepatitis C virus. It is a rapidly progressive, painful, ulcerative keratitis, which initially affects the peripheral cornea and may spread circumferentially and then centrally. Mooren ulcer can only be diagnosed in the absence of an infectious or systemic cause.


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