Investigation on the impact of outdoor exercise on retinal cone photoreceptor mosaic using adaptive optics scanning laser ophthalmoscopy

PURPOSE: To investigate the impact of exercise and sunlight exposure on the cone photoreceptor mosaic using adaptive optics scanning laser ophthalmoscopy (AOSLO) and to identify associated factors. METHODS: This cross-sectional, observational study involved 114 participants (204 eyes) from Tianjin University of Sport who completed comprehensive evaluations, including epidemiological questionnaires, ophthalmic examinations, and AOSLO examinations. Exercise and sunlight exposure were analyzed as the main independent factors, and their joint effect was assessed with mixed-effects models. The high-exercise group was defined as ≥2 hours of exercise per day continuously for 3 years, and the high-sunlight group as ≥2 hours of sunlight exposure per day. Participants were then classified four groups in a 2 × 2 design: high exercise + low sunlight, high sunlight + low exercise, high exercise + high sunlight, and low exercise + low sunlight (reference group). The reference group was used to estimate the effects of exercise, sunlight, and their combination. RESULTS: In independent factors analysis, there was no significant difference in the cone morphology between the high-exercise group and the high-sunlight-exposure group compared with control groups, respectively (P > 0.01). In the joint effect analysis, high-exercise and high-sunlight-exposed significantly increased cone density at the eccentricity 1.5°-2.5° (β= 3252.516, 2389.211, 1853.936, P=0.001, 0.002, 0.003). Axial length mediated this association (P<0.001). CONCLUSIONS: Compared to those receive less exercise and sunlight, participants accustomed to more than 2 hours of daily outdoor exercise had higher cone density. This suggests that outdoor exercise is related to cone photoreceptor health, whereas either sunlight exposure alone or exercise alone failed to produce the combined effect of outdoor exercise.