Rapid response of choroidal thickness to outdoor light exposure in children

Abstract The objective of this study was to explore the rapid changes in choroidal thickness across a wide area of the eye after exposure to intense outdoor light in children.Thirty-five Chinese participants aged between 7 and 15 years old were allowed to acclimate to indoor light (300 lx, “normal light”) for 30 min and then exposed to bright outdoor light (10,000–20,000 lx, “bright light”) for 30 min. Choroidal thickness was measured by optical coherence tomography at five timepoints (completion of the acclimation to normal light and at 2, 5, 15, and 30 min after the completion of outdoor bright light exposure). All post-exposure measurements were obtained after participants had finished the full 30-min outdoor exposure and returned indoors. All experimental data were collected from 8 to 10:00 am. Choroidal thicknesses in each of the nine Early Treatment of Diabetic Retinopathy Study (ETDRS) macular regions were compared between before and after bright light exposure and among these regions. At 2 min after bright light exposure, the choroidal thicknesses of the ETDRS 1-mm zone, the temporal and nasal quadrants of the ETDRS 3-mm zone, and the temporal quadrant of the ETDRS 6-mm zone decreased significantly compared with the baseline measurements. At 5 min, the same was found in all quadrants of the ETDRS regions. At 15 min, the same was found in all except for the superior quadrant of the ETDRS 6-mm zone and the temporal quadrant of the ETDRS 3-mm zone. After 30 min, the same was found in the superior quadrant of the ETDRS 3-mm zone. These findings indicate that exposure to intense outdoor light resulted in rapid and unexpected thinning of the choroid in children over the short term.