Spending too much time in the sun without wearing sunglasses could be why some people develop exfoliation syndrome (XFS).
The eye condition is a leading cause of secondary open-angle glaucoma and can also increase the risk of cataracts, Massachusetts Eye and Ear Infirmary reported.
"The discovery that common genetic variants in the lysyl oxidase-like 1 gene (LOXL1) are associated with 99 percent of XFS cases represented a significant advance in our understanding of this condition," said the study's lead author, Louis Pasquale, M.D., Associate Professor of Ophthalmology at Harvard Medical School (HMS), and director of the HMS Glaucoma Center of Excellence and Mass. Eye and Ear Glaucoma Service and Telemedicine Service. "However, 80 percent of control individuals also harbor these variants and that ratio of cases to control individuals with trait-related variants is fairly similar in regions where XFS is very prevalent and in regions where the condition is relatively rare; this suggests that other genetic or environmental factors contribute to XFS."
Past studies have shown the extent of solar exposure on the eyes is an important risk factor for XFS, but detailed lifetime solar exposure had never been analyzed. Researchers worked to assess the relationship between residential history, solar exposure and XFS.
The researchers conducted a clinic-based, case-control study in the U.S. and Israel involving both XFS and control individuals; all of the participants were over the age of 60 and Caucasian. The team used questionnaires to determine weighted lifetime average latitude of residence and average number of hours per week spent outdoors.
They found with each degree of weighted lifetime average residential latitude away from the equator, there was an 11 percent higher chance of XFS. Every extra hour per week spent outdoors during the summer, averaged out over the course of the individual's lifetime, was linked to a 4 percent increase in XFS risk. For every 1 percent of average time the individual spent outdoors but wearing sunglasses in the summer between the hours of 10 a.m. and 4 p.m., the odds of XFS were decreased by two percent; these findings were only true in the U.S.
"Lifetime outdoor activities may contribute to XFS," Dr. Pasquale said. "The association between work over snow or water and the lack of association with brimmed hat wear suggests that ocular exposure to light from reflective surfaces may be an important type of exposure in XFS etiology. If confirmed in other studies, there could be reason to consider more widespread use of UV-blocking eyewear in these cases to help prevent XFS."
