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Cindy Karouta, Kate Thomson, Regan Scott Ashby; Correlation between bright light and lens-induced myopia. Invest. Ophthalmol. Vis. Sci. 2018;59(9):676.
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In chicks, bright light retards the development of form-deprivation myopia (FDM) in an intensity-dependent manner and slows the rate of compensation to negative lenses. However, it is unclear if lens-induced myopia (LIM), often referred to as a ‘closed-loop’ system due to its defined end-point, is also affected in an intensity-dependent manner as seen in the ‘open-loop’ system of FDM. Therefore, this study investigated the effect of different light intensities on the rate of compensation for negative lenses and whether the dopaminergic system underlies the ability of bright light to inhibit the rate of compensation for LIM, as is seen for FDM.
Chicks were fitted with -10D lenses until compensation occurred (n=10 per group) and reared under the following conditions: 1) 500lux; 2) 10,000lux; 3) 40,000lux; and 4) 40,000 lux with daily intravitreal injections of the D2 receptor antagonist spiperone (0.5mM). Refraction was measured daily, with axial length measured at the start and following lens compensation. Data are presented as means ± standard error, with statistical analysis undertaken by a repeat measures ANOVA followed by student t-test with Bonferroni correction for multiple testing.
Chicks under 500lux compensated to -10D lenses after 6 days of treatment (-8.1±0.2D, 1.24±0.25mm change in refraction and axial length respectively), while chicks kept under 10,000lux took 8 days to show full compensation to match those under 500lux (-7.8±0.4D, p=0.065, 1.22±0.37mm, p=0.7, change in refraction and axial length respectively). Chicks reared under 40,000lux took 10 days to show full compensation (-7.4± 0.3D, p=0.087, 1.31±0.14mm, p=0.9, change in refraction and axial length respectively). Chicks reared under 40,000lux and treated with spiperone showed a similar rate of compensation to those reared under 500lux, showing full compensation by day 7 (-7.6± 0.3D, p=0.058, 1.35±0.23mm, p=0.87, change in refraction and axial length respectively).
The rate of compensation for -10D lenses was inhibited by bright light exposure in an intensity-dependent manner, with the greatest effect seen at 40,000lux. Daily injection of the dopamine D2 receptor antagonist spiperone, however, blocked the effects of bright light exposure, suggesting that as with FDM, compensation for negative lenses is inhibited by light-induced changes in retinal dopamine levels.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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