Using swabs of various parts of the eye and genetic sequencing, researchers from New York University's Langone Medical Center compared the quantity and types of bacteria on the surface of eyes of contact lens wearers and those who do not wear them. They found notably higher bacterial diversity in the former group.
Scientists believe this may help explain the long-standing problem of why contact lens wearers are more prone to eye infection. The Centers for Disease Control has estimated that Americans make almost 1 million doctor's appointments or ER visits for eye infections.
"Our research clearly shows that putting a foreign object, such as a contact lens, on the eye is not a neutral act," senior study investigator Maria Gloria Dominguez-Bello, said in announcing the research in a presentation at the American Society for Microbiology annual meeting on Sunday.
The researchers said that the microbiome of contact lens wearers more closely resembled that of the skin than of non-wearers' eyes. Contact lens wearers had 5,245 distinct bacterial strains and subtypes. They had three times the usual proportion of four of them:
- methylobacterium (often found in soil, sewage, and leaf surfaces),
- lactobacillus (typically considered "friendly" bacteria that live in the digestive and urinary tract and does not cause disease),
- acinetobacter (found in soil and water and responsible for the great majority of infections),
- and pseudomonas (widely found in the environment and that can lead to everything from ear infections to more serious issues).
Surprisingly, contact lens wearers had less staphylococcus on their eyes. Many strains of that bacteria harmlessly co-exist on our skin but some superstrains have been linked to a growing number of serious antibiotic resistant infections in recent years. The researchers said they didn't have an explanation for the lower amount of staph bacteria.