Corneal Ulcers - The Golden Rules of Management

A corneal ulcer is characterized by loss of corneal epithelium. With progression, especially in the presence of enzymes with collagenase activity, the corneal stromal becomes involved. Ultimately, corneal perforation and intraocular involvement with visual loss are possible. The golden rules of ulcer management are designed to prevent this progression.

1. Find and remove the primary cause

All patients with ulcers should undergo a very thorough examination aimed at determining and removing/correcting/treating the cause. Failure to do so is one of the most common reasons for an ulcer not to heal or to heal but recur. Because corneal epithelium is constantly being abraded and desiccated but is protected from excess abrasion by the eyelids and tears, ulcers may be thought of as arising when this situation becomes unbalanced. I.e., there is decreased corneal epithelial protection (tear film or eyelid dysfunction) or increased corneal abrasion (exogenous or endogenous friction). Therefore, causes can be divided into those explained by eyelid, eyelash, or tear abnormalities, foreign bodies, exogenous trauma, or a very limited number of microorganisms.

2. Exogenous trauma is a diagnosis by exclusion

Because of the long list of possible causes, ulceration due to unwitnessed exogenous trauma should be diagnosed only after exclusion of all other potential causes. This requires Schirmer tear testing, assessment of palpebral reflexes, thorough examination of lid and conjunctival anatomy and function (including the posterior face of the third eyelid), and consideration of infectious causes.

3. Other than herpesvirus, infection does not cause ulceration

Although secondary bacterial infection is one of the most feared ulcer complications, no bacteria initiate corneal ulcers in small animals. In dogs and cats, the only organisms known to initiate ulcers are feline and canine herpesviruses. Treatment of these ulcers is addressed by the first rule: “find and treat the primary cause”. [...]