Everyone knows that freckles are a sign you’ve had too much sun—and that your skin might need some extra attention when you’re out in the sun. They show up because the skin is producing excess melanin in an attempt to protect itself from further damage from the sun. It’s also common knowledge that the same UV rays that cause freckling of the skin can also damage your eyes, leading to cataracts and other vision problems. In fact, just like the skin, the eyes can “freckle” from too much sun; and just like skin-freckles, eye-freckles (dark spots on the colored part of the eye—aka, the iris) can be a sign you’ve already had more than your fair share of sun over the course of your lifetime. That’s what Austrian researchers discovered in a study that was recently published in the journal, Investigative Ophthalmology & Visual Science.
For the study, Austrian ophthalmologists piggy-backed onto a skin cancer screening program that was happening at a number of public pools in Styria, Austria. Researchers had comprehensively examined more than 600 people between the ages of four and 84 for freckles—including the eyes. These volunteers had also filled out a questionnaire about how much sun they’ve gotten in their lives, how many sunburns, and what they do for sun protection. What the doctors discovered was that the development of eye freckles was very similar to those that turn up on your skin: If you have lighter-colored eyes and have had a lot of sun exposure—especially a history of blistering sunburns—your eyes are more likely to freckle.
Although eye freckles are not cancerous themselves, say the researchers, they offer an obvious and easily visible marker for the sun damage that can trigger skin cancer. “We now have a [marker for] chronic sunlight exposure,” study author Christoph Schwab, MD, ophthalmologist at the Medical University of Graz in Austria, told Science Daily. In addition, further scientific study of eye freckles can lead to a better understanding of the role that sunlight plays in eye diseases and conditions such as cataracts and macular degeneration.
It should be noted that in very rare cases, eye freckles can change into skin cancer, according to New Zealand eye surgeon, Malcolm McKellar, MD. These cancers grow slowly but will eventually threaten the eye and vision if left untreated, and in approximately ten percent of cases can lead to death (if the tumor is melanoma and spreads to other parts of the body).