Traditional assumptions have held that contact lenses are safer than laser surgery to correct vision problems. Now, an Oregon Health & Science University Casey Eye Institute physician, comparing data from several recent studies, has found that belief may not be true.
"Several times a year, I have patients who lose eyes from complications because they've been wearing contacts and they've gotten an infection. By this I mean their eyes have to be physically removed from their bodies," said Mathers, an eye surgeon with a strong background in contact lens issues and former president of the Contact Lens Association of Ophthalmologists. "It's not that contacts aren't good. They're better than they've ever been. But one cannot assume contacts are safer."
The risks associated with laser surgery versus contact lenses can not be compared directly, partly because complications from contact lenses accumulate over years of use, and complications from surgery occur soon after the surgery.
Data extrapolated from a study in Lancet shows the lifetime risk of bacterial keratitis to be 1 in 100 for contact lenses worn daily. Bacterial keratitis is an infection that causes an inflammation of the cornea and can lead to vision loss. Wearing contact lenses overnight or improper care or cleaning further increases the risk of infection from contacts. The risk of bacterial keratitis has changed little over the years for contact lens wearers and is the same worldwide.
Vision loss from laser surgery is easier to calculate. Mathers looked at a large study of military personnel who had laser surgery and found results similar to those of the OHSU Casey Vision Correction Center.
A study of more than 32,000 U.S. Armed Forces members receiving laser surgery published in the journal Ophthalmology found a loss of vision of one line on an eye chart was 1 in 1,250. A loss of two or more lines of vision, which would be more significant, but less frequent, was not reported. Data from the OHSU Casey Vision Correction Center showed no cases of vision loss greater than two lines in 18,000 procedures performed over 10 years.
"Even with perfect care of your contacts, the risks for infection and vision loss are still there," said Mathers. "Our long-term results at OHSU confirm the experience of the U.S. military: Laser surgery is as safe, and probably safer, than long-term use of contact lenses."
The calculated risks of vision loss from contact lenses and laser surgery are approximate and subject to change. Highly oxygen-permeable contact lenses and advances in laser surgery should make both even safer. There are approximately 20 million to 25 million contact lens wearers in the United States, and approximately 1 million people in the United States have laser surgery every year.
"Data from these studies strongly suggest our intuition regarding these risks needs to be reassessed," Mathers said. "I, for one, look forward to further investigations of these risks."