Ulcers of the cornea — the transparent front layer of the eye — may be twice as common in the U.S. as previously thought, likely owing to the recent rise in contact lens use, suggests a new study.
Based on more than a million people in northern California, researchers found that contact lens wearers were about 9 times more likely to develop the eye condition compared to non-wearers.
"As new contact lens innovations become available, and people hear that they can wear these contact lenses for weeks or a month without taking them off, they do just that. They don't realize the dramatic increase in risk it causes them," researcher Dr. David Gritz of Montefiore Medical Center in New York told Reuters Health. "Our eyes do need breaks from contact lens wear."
Corneal ulcers are open sores usually caused by viral or bacterial infections, which frequently follow an injury as minor as a small scratch in the thin layer of tissue protecting the cornea. The result can be severe pain, even permanent vision loss.
Gritz, along with lead researcher Dr. Bennie Jeng of the University of California, San Francisco, and their colleagues studied 1,093,210 patients treated in the Northern California Kaiser Permanente Health Care Program. The team collected information on presence of corneal ulcers, as well as contact lens use, eye trauma or disease, and HIV status.
A total of 302 patients (0.03 percent) developed corneal ulcers over a 12-month period between 1998 and 1999. Extrapolating this figure to all of the U.S., where 38 million people currently wear contact lenses, suggests that about 71,000 new cases of corneal ulcers are diagnosed every year, or about 23 cases per 100,000 people.
A handful of small studies in the past had estimated an annual rate of about 11 cases per 100,000 people, the authors note. Even that figure represented an increase from 2.5 cases per 100,000 people in the 1950s.
While contact lens wearers accounted for 12 percent of all patients in the current study, this group received more than half of the corneal ulcer diagnoses.
People with known HIV infection also had about a 9-fold higher risk of the condition compared to patients that were HIV-negative, report the researchers in the Archives of Ophthalmology.
"This is the first time that we've been able to say that HIV infection alone appears to be a significant risk factor for developing a corneal ulcer," said Gritz. "If someone has HIV infection, they need to be very attentive to their eyes."
Another particularly at-risk group highlighted by the study was young women. Their relatively high rate of corneal ulcers — double that of similarly aged men — might be due to the popularity of cosmetic contact lenses, hint the researchers.
The rises in availability of disposable and overnight contact lenses, and the ease of Internet ordering, are potentially dangerous, noted Gritz. "People need to get properly fitted for contact lenses, and seek follow-up care by an eye care professional," he said. "Contact lenses can even act as a bandage over eye irritation, covering up symptoms. So people need to listen to what their eyes are telling them, and always have a good pair of glasses available as an alternative."