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Molly Fellows, Gagan Kaur, Ashley Tang, Frances Rucker; Luminance and Color Changes with Defocus Provide Differential Cues For Emmetropization. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2328.
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Factors that interfere with lens compensation are considered to interfere with emmetropization. We examine the effects of color and luminance changes on lens compensation.
Exp. 1: 5-7 day old chicks were exposed daily (9am-5pm) for three days, on consecutive weeks, to 2Hz sinusoidal, in-phase (LUM), modulated white light (619 nm + 515 nm + 460 nm; Mean 680 lux) or to counterphase-modulated red/green light (R/G). Chicks wore either a negative or a positive 7 D lens on alternate weeks. Exp. 2: 14 day old chicks were exposed daily (9am-5pm) for three days to 2Hz sinusoidal, in-phase, modulated white light (619 nm + 515 nm + 460 nm; Mean 850 lux) either with (+B) or without blue light (-B). Chicks wore either a negative or positive 7 D lens on one eye. Chicks wore no lenses in a control, no flicker condition. Chicks were kept in the dark overnight after exposures and otherwise in a brooder on a 12/12 hr light cycle between experiments. Relative changes in the ocular components were measured with ultrasound (Exp.1) or with Lenstar (Exp. 2) and with a Hartinger refractometer.
Exp. 1: LUM flicker, but not R/G flicker, interfered with positive lens compensation. There was a change in refraction in R/G (wk1: 4.93 ± 2.116 D; p=0.02) but not in LUM (wk1: 2.43 ± 2.68 D), despite a reduction in eye growth in all conditions (R/G: -196 ± 30 μm; LUM: - 139 ± 24 μm; p<0.006) with choroidal thickening in R/G but not in LUM (RG: 53 ± 18 μm; LUM: 14 ± 16 μm; p<0.01). LUM flicker and R/G flicker both interfered with negative lens compensation. There was no refractive (wk1: R/G: -1.76 ± 1.13 D; LUM: -1.64 D), eye growth (RG: 24 ± 48 μm; LUM: -4 ± 23 μm), or choroidal thickness change (-1 to -6 μm). Exp. 2: There was no refractive change with or without blue light to positive (+B: -0.47 ± 2.7 D: -B: 0.32 ± 3.03 D) or negative defocus (+B: -0.77 ± 2.4 D; -B: -1.65 ± 1.19 D), compared to steady light/no lens condition (+B: -0.25 D; -B: 0.51 D). However, with positive lenses there were changes in eye length (+B: -219 ± 36 μm; -B: -228 ± -28 μm; both p<0.001) and choroidal thickening (+B: 124 ± 14 μm; -B: 132 ± 20 μm;both p<0.001) compared to the steady light/no lens condition (+B: -50 µm; -B: -20 µm).
Luminance cues are important for lens compensation with both signs of defocus, while color cues are only important with negative defocus.
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