Overnight use of extended-wear contact lenses is the main risk factor for a potentially blinding form of eye infection, according to Dutch researchers. The investigators focused on the prevalence of microbial keratitis, a rare form of bacterial eye infection associated with contact lens use. In a minority of cases, microbial keratitis can result in corneal damage leading to partial or total blindness in the affected eye.

The risk of microbial keratitis was 18.9 times greater for users of extended-wear soft contact lenses and 3.3 times greater for users of daily-wear soft contact lenses than for users of daily-wear hard lenses, according to the authors. They investigators blame the high infection risk of extended-wear lens users on the users’ tendency to keep contacts in overnight.

The Lancet July 17 1999;354:174-175, 179-183.

COMMENT: This is not new information, however, it is useful to be reminded of the basics. Contacts, and glasses, also serve as a filter and do not allow all 1500 wavelengths of sunlight to pass through to the retina where they are absorbed into the brain. Wearing glasses or contacts continuously will certainly increase your risk of depression, as your brain will be deprived of many of the valuable frequencies that are in sunlight. One should also be cautious of laser keratotomy, which reshapes the cornea so one does not have to wear glasses or contacts. There are two concerns here. The first is that the laser will produce scars on the cornea that may impair energy transfer in the body. The second one is that most of us will require reading glasses as we hit our mid 40s. This will put one right back into the corrected vision category again.