Anaerobic flora of the normal human conjunctival sac

Specimens from the conjunctival sacs of 92 healthy eyes were cultured on two separate occasions to determine the presence or absence of a persistent anaerobic flora. Aerobic bacteria and fungi were also studied for comparison. Of the 184 eye cultures, 112 (60.9%) contained at least one microorganism. Obligate anaerobes were recovered from 51.6% (95/184) of the cultures. Propionibacterium acnes, the predominant anaerobe encountered, was present in 49.5% (91/184) of the eyes. Aerobic and facultatively anaerobic bacteria, present in 32.6% of the total eye cultures, were less common than obligate anaerobes. Staphylococcus epidermidis was the most common of these. Fungi were rarely found. Our findings suggest that the conjunctival sac is either sterile or normally contains small numbers of anaerobic, aerobic, or facultatively anaerobic bacteria. As other workers have suggested, the origin of the bacteria in the eyes may be the skin of the eyelids.