Short-term effects of sunlight exposure on fundus blood flow perfusion in children: a randomised controlled trial

Abstract

AimTo evaluate the short-term effects of different sunlight exposure on fundus blood flow perfusion (BFP) after near work.MethodsIn this parallel randomised controlled trial, 81 students aged 7–15 with spherical equivalent refraction between −2.00 and +3.00 diopters were randomly assigned to either a low-illuminance (4k lux) group (N=40) or high-illuminance (10k lux) (N=41). Following 1 hour indoor reading, participants had sunlight exposure matching their group’s intensity for 15 minutes. BFPs in the superficial retina, deep retina and choroid were measured at four time points: pre-reading, post-reading, 5th-minute and 15th-minute sunlight exposure.ResultsWithin the initial 5 minutes of sunlight exposure, the 10k lux group showed a tendency for decreased BFP, particularly in the choroid (superficial retina: −0.2, 95% CI −0.9 to 0.5; deep retina: −0.1, 95% CI −0.6 to 0.4; choroid: −0.4, 95% CI −0.8 to 0.0), while the 4k lux group exhibited an increase (superficial retina: 0.7, 95% CI 0.1 to 1.3; deep retina: 0.3, 95% CI −0.2 to 0.8; choroid: 0.1, 95% CI −0.2 to 0.5). From 5 to 15 minutes, BFP decreased in both groups. At the 5th-minute mark, the 10k lux group exhibited a greater decrease in choroid (10k −0.4 vs 4k 0.1, p=0.051). No significant difference was observed after 15 minutes of exposure.ConclusionHigher illuminance sunlight exposure can restore fundus BFP more rapidly than lower; however, duration remains pivotal. To prevent myopia, continuous sunlight exposure for over 15 minutes is recommended to aid in reinstating the fundus BFP increased by near work.Trial registration numberNCT05594732.