Sun exposure as a risk factor for precipitating vision loss for individuals with LHON mitochondrial variants

Vision loss in Leber hereditary optic neuropathy (LHON, OMIM# 535000) is caused by pathogenic LHON associated mitochondrial DNA (mtDNA) variants that are often considered to be triggered by a second environmental stress (genotype-­ environmental double hit). A few studies have demonstrated associations between the onset of LHON vision loss and specific environmental stresses such as tobacco or alcohol use. Other plausible triggers, such as UV exposure through sunlight, has not yet been studied. The purpose of this study was to survey LHON patients’ lifestyle and habits to investigate the risk of light exposure on this population, including the correlation of the time of year vision-­loss was triggered. We collected information on their daily smoking habits, alcohol use, and sun exposure for months before and during the time of vision loss. We did not find a strong correlation between sun exposure and onset of vision loss, though we cannot rule out a contribution in precipitating the LHON phenotype since individuals who lost their vision in adulthood reported longer sun exposure, and more total exposures, then individuals who lost their vision in youth. This study contributes to the growing body of literature regarding environmental influences of LHON blindness, and we suggest that UV exposure still requires further investigation to understand what, if any, role it may play