Discussion

Is it possible that improper cleaning of the tonometer tip can lead to false positive staining because the agent used to disinfect the tip is not completely removed and causes a chemical burn locally?

Richard L. Lindstrom, MD: Yes. The punctate staining can be a false positive, but it is something that requires a careful look. In this case, false positives are not necessarily a problem. If every eye with fluorescein staining from the tonometer is further examined by a staining with lissamine green, the fluorescein staining, something that is performed for every patient anyway, becomes a sensitive screening tool.

Do data from Ocular TRUST depend on factors associated with the antibiotic, such as whether the drug has a high concentration on the surface?

Penny A. Asbell, MD, FACS, MBA: That is a valid point, because when we choose an antibiotic we are considering several modalities. One is its potency—does it cover a lot of organisms? Does it cover the methicillin-resistant organisms? Equally important are the pharmacokinetics of the antibiotic in question. Does it penetrate the tissue, and does it stay there?

Those are important considerations, and there are definitely differences among the fluoroquinolones in terms of their ability to penetrate and to remain in the tissue. So, those are other characteristics that should be considered, particularly when a new antibiotic or a new use of an antibiotic is discussed. Physicians should not rely on lab testing alone. The interaction of the organism with a person is important as well. This is one of the reasons why topical agents are sometimes effective against eye infections, but may not be effective in a systemic infection.

In the monocular case patient colonized with MRSA, both the eyes and the nares were cultured. Is that a routine part of practice or was this done because this was a high-risk patient?

Terrence P. O’Brien, MD: This is not routine. Culturing both the eyes and nares is only conducted for a high-risk patient like this who has had a prior incident that has led to loss of the eye—the source may be the nasopharynx. I culture the conjunctiva but not the lid margin.

Did you treat the nares in the monocular woman colonized with MRSA?

O’Brien: We did treat the nares with mupirocin. Mupirocin is an agent that is available in an ointment form that can be applied in the nares. However, when the organism was analyzed, it was found to be resistant to mupirocin. There has been some increasing resistance to mupirocin because it is widely used by dermatologists, general surgeons, and others as an ointment. So, mupirocin is losing some of its efficacy.

Do you use bacitracin ophthalmic ointment?

O’Brien: Bacitracin is a useful agent for patients who have lid margin disease. The laboratory data do support its continued efficacy.

Lindstrom: Bacitracin is useful as an adjunct as well.