• Two hundred twenty in-use medications from 101 patients with nonmicrobial ocular surface disease were studied by culturing the bottle caps, a drop produced by simple inversion, and the interior contents removed sterilely. Conjunctival cultures were taken from these patients and 50 age-matched controls. Pathogenic organisms were harvested from conjunctivae significantly more frequently (P<.01) from cases (34 of 101) than from controls (five of 50). Sixty-four medications (29%) had microorganisms cultured from at least one medication site. Gram-negative organisms were significantly more likely (P<.00001) to be isolated from all medication sites than gram-positive organisms. Additionally, when isolated from medication sites, the gram-negative organisms were highly likely to be cultured from the conjunctiva as well. This was not true for pathogenic gram-positive organisms. We conclude that a cycle of contamination between inuse medications and conjunctivae may represent an important risk factor for microbial keratitis in patients with ocular surface disease.
Schein OD, Hibberd PL, Starck T, Baker AS, Kenyon KR. Microbial Contamination of In-Use Ocular Medications. Arch Ophthalmol. 1992;110(1):82-85. doi:10.1001/archopht.1992.01080130084030