People who wear contact lenses may be more susceptible to eye infections because wearing them alters the types of bacteria found on the surface of the eye, according to a small US study.

Researchers at the NYU Langone Medical Center found more bacterial diversity on the surface of the eye than on the skin directly beneath the eye.

They also found that the eyes of contact lens users had 3 times the usual levels of certain bacteria – Methylobacterium, Lactobacillus, Acinetobacter, and Pseudomonas – than the eyes of those who did not wear contact lenses.

‘A foreign object’

“Our research clearly shows that putting a foreign object, such as a contact lens, on the eye is not a neutral act,” says microbiologist Maria Dominguez-Bello, who led the research.

The results have been presented this week at the annual meeting of the American Society for Microbiology in New Orleans, but have not yet been published in a peer-reviewed journal.

The scientists reached their conclusions by taking eye and skin swabs from 9 contact lens wearers and 11 people who did not wear lenses.

Preventing infections

Co-author Dr Jack Dodick, who heads the ophthalmology department at NYU Langone, points out an increasing number of cases of corneal ulcers following the introduction of soft contact lenses in the 1970s. “A common pathogen implicated has been Pseudomonas,” he says in a statement. “This study suggests that because the offending organisms seem to emanate from the skin, greater attention should be directed to eyelid and hand hygiene to decrease the incidence of this serious occurrence.”

According to the British Contact Lens Association, severe infections of the cornea are extremely rare. It says daily disposable lenses, first introduced in 1995, have the lowest risk of this complication of all soft lenses when used correctly.