Treat contact lens-related microbial keratitis as bacteria until proven otherwise

March 1, 2011

Microbial keratitis that arises from contact lens wear can be a delicate subject.

"The incidences of [MK] are so small, and the occurrences so rare, that we really don't get a sense of patterns," said Dr. Epstein, of North Shore Contact Lens and Vision Consultants, New York. "And patterns and pattern recognition are important ways that we refine our clinical skills. Ironically, these two outbreaks that caused so much misery were helpful in that they allowed us to observe patterns that we'd otherwise not see."

From differential to management

"The first step when dealing with a keratitis is to determine if it's sterile or infectious," he said. "The next step is to determine the causative pathogen: bacteria, virus, fungus, or Acanthamoeba."

To help you determine the cause of the keratitis, Dr. Epstein advised starting with a thorough history, including CL wear and solutions used, contributory medical problems, current ocular medications, recent trauma to the eye, and recent travel.

"The role of staining caused by [CL] care products is somewhat controversial," he said. "Every textbook likens staining-or almost anything that disturbs external corneal barriers-as a pre-disposing factor to infection. The question then becomes if staining caused by [CL] wear or products is a factor in increased risk of infection. I don't know that staining is a 'smoking gun,' but I do think as clinicians we have to consider it suggestive."

When performing slit lamp examination on these patients, do not let their photosensitivity cause you to reduce the slit lamp intensity, Dr. Epstein advised.

"Yes, these patients are in pain, but they are counting on you to help them," he said. "That means getting to best view you can so you can make the correct diagnosis and initiate the correct treatment as soon as possible. Almost every patient is empowered by the feeling that they are teaching you something that may help them or someone else. They are willing to put up with significant discomfort for that."

Smears and cultures are indicated prior to initiating treatment in sight-threatening and severe keratitis, and when the patient has deep and large stromal infiltrates involving the visual axis.