Short-term impact of natural daylight exposure on choroidal thickness in emmetropic young adults

Abstract

Background: Exposure to light has been identified as an important factor in the control of eye growth and the development of refractive error.
Aim: The aim of this article is to examine the short-term impact of natural daylight exposure on choroidal thickness (ChT).
Setting: The study was conducted at Qassim University, Saudi Arabia.
Methods: In this prospective study, 60 healthy emmetropic adults aged 19 years – 26 years completed comprehensive eye examinations. Choroidal thickness was measured using Swept-Source Optical Coherence Tomography with radial scans across macular regions. Two experimental sessions were conducted under indoor illumination (200 lux) and another involving 1 h of outdoor daylight exposure (~20 060 lux). Baseline indoor Optical Coherence Tomography scans were collected, followed by post-exposure scans obtained after 1 h of either indoor or outdoor light conditions. General linear model-repeated measure was used to examine ChT changes across light conditions and macular regions.
Results: Across all macular regions, no statistically significant differences were found between baseline and post-exposure measurements (all p > 0.05), except in the inner temporal macular region (p = 0.046). Baseline subfoveal ChT was similar between sessions (297 μm ± 69 μm indoors; 298 μm ± 67 μm outdoors), with no changes after 1 h in both light conditions.
Conclusion: The results showed that natural daylight exposure for 1 h produced no measurable changes in ChT under the conditions of this study, with all variations considered within normal diurnal fluctuations. Future research should consider factors that influence ocular responses, including diurnal variations in ChT and the characterisation of choroidal responses to light exposure.
Contribution: This study provides evidence that the human choroid shows limited short-term responsiveness to light exposure, with all variations considered within normal diurnal fluctuations.