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Manrong Yu, Christine Frances Wildsoet; The complementary inhibitory effects of short wavelength lighting and myopic defocus on eye growth in chicks. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4812. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Early eye growth, which underlies emmetropization, is strongly influenced by visual environmental factors, including optical defocus and lighting characteristics. Previous studies in chicks have reported independent inhibitory effects on myopia progression of both blue lighting and myopic defocus. The aim of the study reported here was to investigate the effects of blue lighting and myopic defocus incorporated into dual-power (Fresnel) lenses, presented alone or in combination, on eye growth in young chicks.
Two groups 25 chicks wore either +10/-10 D Fresnel lenses (FL) (50:50, n=13) or -10 D single vision lenses (SV) (n=12) over their right eyes for 7 days from 3 days of age. Subgroups of both were reared in either diurnal white light (60 chick lux) or blue light (60 chick lux, 460 nm). Refractive errors and axial eye dimensions were measured before and on day 3, 5 and 7, after the interventions using retinoscopy and ultrasonography, respectively. Two-way repeated measures ANOVA and unpaired t-tests was used to analyze the effects of the lens treatments and lighting conditions.
Pre-treatment ocular parameters were comparable across groups. The type of lens, lighting characteristics and treatment duration all influenced affected the refractive error outcome (F=5.38, p=0.013). Myopia progression was evident in both SV lens groups, although less under blue compared to white lighting, while the FL lens groups showed hyperopic shifts in refractive error, more so in blue lighting, as reflected in end-of-treatment interocular differences (SV lens groups: -5.09 vs. -10.16 D: p<0.001; FL lens groups: +3.29 vs. +1.11 D, p=0.02) (Fig. 1, Table 1). Axial length and vitreous chamber depth changes were consistent with the refractive error changes, with myopia progression coupled to increased elongation and hyperopic shifts coupled to reduced elongation (Fig. 1, Table 1).
Both short wavelength (blue) light and myopic defocus imposed via dual power lenses are protective against defocus-induced myopia and their effects appear to be additive. Whether shorter-term exposure to blue light and/or simply biasing lighting towards short wavelengths can also offer significant protection against myopia progression warrants investigation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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