This study identified an increased risk of early AMD with moderate lifetime UVR exposure, but no dose-response relationship was established. Photo: Carolyn Majcher, OD. Click image to enlarge.

There is growing evidence that long-term exposure to ultraviolet (UV) radiation can be harmful to the retina and could increase one’s odds of developing age-related macular degeneration (AMD), but studies have shown conflicting results when evaluating the associations. A longitudinal study conducted in France investigated the association between the two. Researchers found an increased risk of early AMD with moderate lifetime UVR exposure, but no dose-response relationship was established.

A total of 963 participants over the age of 73 were included. A subset of 614 participants with advanced AMD and another 422 with early AMD were included. The participants' residential history combined with UVR estimates in the region were used to approximate the amount of ambient UVR they have been exposed to over their lifetimes. AMD was classified from retinal fundus photos and SD-OCT at two-to-three-year intervals between 2006 and 2017. Associations between cumulative exposure to ultraviolet exposure (UVA, UVB and total UV) and the incidence of early and advanced AMD were estimated.

For those with early AMD, previously published cross-sectional results showed that participants with the most and least lifetime ambient UV exposure had an increased risk of early AMD compared to participants in the intermediate range, the authors explained.

The findings of the present study could be associated with the accumulation of high-intensity UV, which can exceed the filtering capabilities of the mature human lens, resulting in damage to the retina as a result of an inflammatory response, according to the authors.

“Although melanin in the retinal pigment epithelium and choroidal areas can absorb UV radiation and prevent retinal aging damage, it can be photobleached, reducing its protective impact against such damage,” the authors explained in their paper for Retina. “This may be observed for the older participants in our sample,” they wrote, although subjects with highest UV exposure were not associated with early AMD. The researchers suggest this “may be explained by the heterogeneity of our population; indeed, participants living in places with high sun exposure may have different habits (regarding sun exposure and protective measures adopted to protect oneself or not) and/or different genetics (particularly for the populations from North Africa).”

Among subjects with advanced AMD, no association was found with lifetime UV exposure. Previous studies found similar results and reported that outdoor leisure activities were not associated with the incidence of advanced AMD.

The team wrote that their study suggests an increased risk of early AMD for participants with intermediate (vs. low) UV exposure. However, the authors could not confirm a dose-response effect of UR exposure on early AMD onset.

“These results confirm previous observations indicating a possible association between cumulative sun exposure and the incidence of early AMD; however, this needs to be investigated in other longitudinal studies to reach conclusions about the relationship between sun exposure and the incidence of early and advanced AMD,” the authors concluded.