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Yuval Cohen, IV, Richard A. Stone, V, Arieh S. Solomon, V; Ambient Light Intensity Of Fluorescent Versus Incandescent Light And The Emmetropization Process Of The Chick's Eye. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3442.
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Chicks' emmetropization is dependent on the intensity of ambient incandescent (IC) illumination (Cohen et al., 2011). Myopia, emmetropia and hyperopia develop following 80 days of exposure to 50, 500, and 10 000 lux of light-dark cycle conditions (delineated throughout as low-, medium-, and high-light intensities, respectively). Fluorescent (FL) light, commonly used for indoor lighting, has a different characteristics from incandescent (IC) lighting, such as photon source, continuity of photon emission, and spectral light distribution. In this experiment, we evaluated the effect of ambient light intensity of FL light on chicks' emmetropization, and compared the developing refractions of chicks reared under IC or FL lighting.
Newly hatched white leghorn chicks were raised under FL light (low-, n=18; medium-, n=16; high-, n= 16, intensity of light, respectively). Streak retinoscopy, keratometry, and b-scan ocular ultrasound were sequentially performed from 10 until 90 days post-hatching. Refractive development data under FL light was compared to IC light data (low, n=13; medium, n=14; high, n= 13, intensity of light, respectively) previously reported (Cohen et al., 2011).
The refractions correlated with log intensity of FL light (day 20 r=0.75, p<0.0001; day 90 r=0.92, p<0.0001). Under both FL and IC light, lower ambient light intensity was associated with longer axial lengths, corneal flattening, lens thinning, and deepening of both anterior and vitreous chambers. After 90 days, all chicks exposed to low intensity of FL light developed myopia, with a mean refraction of -1.86±1.1 diopter (D), as compared to -2.4±1.2 D under low intensity of IC light (p=0.09). High intensity FL light resulted in slower ocular growth and a mild hyperopic refraction. On day 90, the hyperopia developed under high intensity of FL light was 0.6 D greater than the hyperopia measured under high intensity of IC light (p<0.0001).
Chicks' emmetropization is influenced by the ambient intensity of both FL and IC light, with minor refractive differences under high intensity light. Like IC light, high and low intensities of FL light are associated with the development of hyperopia and myopia, respectively.
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