October 2010




Sun-sensitizing medications in the light of day

by Maxine Lipner Senior EyeWorld Contributing Editor

    Cortical cataracts potentially linked to medication

C ortical cataracts may be spurred by the use of sun-sensitizing medication in conjunction with sun exposure, according to Barbara E. K. Klein, M.D., professor of ophthalmology and visual sciences, University of Wisconsin, Madison, Wis.. Recent study results published in the June issue of Archives of Ophthalmology indicated that when other risk factors were controlled for, those who used sun-sensitizing drugs and had years of outdoor exposure were more prone to cortical cataracts.

Considering an environmental link

Studying a potential environmental link to cortical cataracts seemed to be a natural move for investigators."Cortical cataract seems to be related to environmental exposures, more so than the other kinds of age-related cataracts," Dr. Klein said. "In the past we have looked at other factors, but certain medications and exposure to sunlight in particular seem to increase the risk." With a very extensive drug database to draw from, investigators decided to take a closer look at a potential connection between certain medication use and sun exposure. "Some medications are thought to be related to sun-sensitizing experiences in the skin," Dr. Klein said. "Because of the similar embryologic background it seemed that it was plausible that the sun exposure effect could be modified by taking medication," she said. This study was an offshoot of the Beaver Dam Eye Study, an epidemiological investigation that followed Wisconsin residents over the course of several years. "We had medication use, photographs of the lens, and a bunch of other information from the people who were involved in the Beaver Dam Eye Study over the course of many years," Dr. Klein said. "We looked at incident cortical cataract, people who didn't have this at the beginning but who we knew what medications they were taking." These patients were seen by investigators every 5 years. Photosensitizing medication considered in this report included a wide variety of pharmaceuticals including diuretics, diabetes drugs, antidepressants, antibiotics, and at least one NSAID. "There are a variety of drugs and a variety of classes that we considered," Dr. Klein said. "Sun sensitivity is a rather nebulous term but it includes rashes as well as itching and that sort of thing." Environmental exposure in the form of Wisconsin sun years was also considered. "Wisconsin doesn't have a lot of sun compared to other places, so it was dichotomized to high and low levels," Dr. Klein said. "Some people had higher levels of exposure consisting only of what our estimates were from this national data about sun exposure at different latitudes."

Making a cortical connection

Together with high levels of exposure, at 15 years out, sun-sensitizing medication seemed to prime patients for cortical cataracts. "The key finding is that neither the sun exposure in the incidence data nor the medication use alone was significantly associated (with cortical cataract), but when you put them together, it was," Dr. Klein said. "It's an interaction of medication and sun exposure."

Cortical cataracts appeared to be the only type influenced by the sun-sensitizing medication in conjunction with heightened exposure. "There was no significant interaction nor was there an individual effect on the other two kinds of age-related cataractone being nuclear cataract and the other being posterior subcapsular cataract," Dr. Klein said. "This seemed to be relatively specific for cortical cataract."

Dr. Klein is not surprised that cortical cataracts appear to be the only ones potentially influenced by the medication. "It is the cataract type that seems to be a bit more influenced by environmental exposures," she said. She stressed that while the information is intriguing, it needs to be substantiated elsewhere. "The information from this study is interesting, but it definitely needs replication elsewhere to see if this holds up," she said. Dr. Klein sees the fact that such results were attained in a more northern latitude area such as Wisconsin as only heightening the potential importance. "I think that it's an interesting observation because the medications are extremely widely used and there are places that get more sun exposure than Wisconsin," she said. "It may be an important interaction to be aware of." The fact that many people are drawn to warmer locales may increase the importance. "At least at one time, there was a great movement of people from cold and wintery places like Wisconsin down south," Dr. Klein said. She surmised that there may still be more people populating the lower latitudes of the United States and thinks that this may be important because many of the sun-sensitizing drugs are widespread in use.

Overall, she stressed that more research is needed. "Someone should repeat this and look in greater depth and also look at mechanisms," Dr. Klein said. "As an epidemiologist, I'm not prepared to talk about the basic science of what this would mean, but I think that this is a fertile area for research."

Editors' note: Dr. Klein has no financial interests related to her commens.

Contact information

Klein: 608-263-7171, kleinb@epi.ophth.wisc.edu

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