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Sekar Ulaganathan, Scott A Read, Michael J Collins, Stephen Vincent; Seasonal light exposure and eye growth variations in young adults. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2739. doi: https://doi.org/.
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Seasonal variations in myopia progression/axial elongation have been documented in studies of pediatric populations, and seasonal differences in light exposure have been hypothesized to play a role in these variations. However, the presence of similar changes in young adults has not been examined. Therefore, in this study, we examined the daily light exposure and longitudinal axial length changes in young adult emmetropes and progressing myopes over two different seasons
Thirty eight young adults (mean age 22 ± 4 years, 19 progressing myopes, 19 emmetropes), had six-monthly measures of axial length (AL) collected over a one-year period, in summer and winter months. Personal ambient light exposure data was also assessed using wrist worn light sensors that were worn in winter (May to August) and summer months (November to February), from which the mean daily (6 am to 6 pm) light exposure was derived. The influence of season and refractive error on the average daily light exposure and the six-monthly changes in AL were examined
Linear mixed model analyses revealed a significant effect of season, refractive error, and a season by refractive error interaction (each p<0.05) for both light exposure and AL changes. In summer, myopes exhibited significantly greater 6-monthly changes in AL (mean change 0.04 ± 0.05 mm) compared to the emmetropes (-0.01 ± 0.05 mm) (p<0.05). However, the difference in AL change was not different between myopes (0.03 ± 0.05 mm) and emmetropes (0.02 ± 0.04 mm) in winter (p>0.05) (Figure 1). A significant interaction between the seasonal AL variations and light exposure was observed (p<0.05). Emmetropes had significantly higher mean daily light exposure in summer (227 lux higher, p<0.05) compared to winter, whereas myopes did not exhibit a significant seasonal variation in light exposure (103 lux higher in summer, p>0.05)
In young adults, six monthly axial elongation and daily light exposure show seasonal variations that appear to differ according to refractive error. When compared to emmetropes, progressing myopes had greater axial elongation and lower light exposure in summer. These findings suggest that seasonal light exposure variations could contribute to seasonal variations in eye growth
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Mean ± SEM six-monthly axial length changes (left) and mean daily light exposure (right) for emmetropes and progressing myopes in winter and summer
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