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When do I culture?
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The availability of monotherapy coupled with economic pressures have made culturing a tricky issue for practitioners who face an infection of unknown etiology.
Bobby Christensen, OD, said economics are certainly a factor. "Cultures are expensive. They can cost the patient from $50 to $150 extra," he said. "You have to have reasons to give insurance companies, and you have to use your professional judgment. If the eye is threatened, you don’t worry about cost. But for minor things, we’ve got antibiotics that will take care of the problem quickly and safely."
J. James Thimons, OD, agreed: "Obviously cost is a consideration when culturing."
Bruce E. Onofrey, OD, RPh, cultures any suspected corneal ulcers and any suspected bacterial keratitis. He also cultures suspected cases of Chlamydia "Optometrists who don’t regularly culture bacterial keratitis put themselves at significant medicolegal risk," Dr. Onofrey said. "The ‘experts’ always culture infectious keratitis. You will be held to this higher standard if you are unfortunate enough to end up in court."
Dr. Christensen does not automatically culture a red eye. "We do culture those that don’t look right, that don’t make sense, that don’t do what you would expect them to do," he said, "as well as unusual injuries to the eye, such as something flying up from a lawnmower."
Fluoroquinolones have changed culturing protocols, said Dr. Thimons. In the past, culturing had a larger role because drugs were gram positive- or gram negative-specific. Fluoroquinolones, with their broad-spectrum coverage, can handle both types of infection.
"I treat the bulk of my patients empirically, as most practitioners probably do," Dr. Thimons said. He said only 1% or 2% of his patients get cultures prior to therapy, and "the results are usually pretty good."
Dr. Thimons uses cultures in patients who have:
- chronic disease and have been managed unsuccessfully by other practitioners;
- central corneal ulcers;
- unilateral disease;
- a physical presentation that does not match their history or symptomatology;
- a fever with a bacterial-based conjunctivitis;
- hyperpurulent conjunctivitis; or
- those who have not responded to therapy or have worsened once therapy was initiated.
Dr. Thimons said in contact lens patients, practitioners need to determine whether an infiltrate is peripheral and if it is a true ulcer. Again, because of fluoroquinolone monotherapy, some practitioners do not culture small, non-centrally based lesions anymore.