Abstract
Purpose :
Previous research (Rucker et al., 2015) has shown that exposure to yellow light (without a blue light component in the light source) at low temporal frequencies induces myopic increases in eye growth compared to white light (with a blue light component). Given that different color temperatures of commercially available artificial illuminants produce varying ratios of long- (L), medium- (M), and short-wavelength (S) cone excitation, we tested the effect of simulating these light sources on the emmetropization of chicks.
Methods :
49 two-week-old chicks (Gallus gallus domesticus) were exposed to 0.2 Hz square-wave luminance modulation (mean= 985 lux, contrast= 80%) for 3 days. LED strips that simulated General Electric (GE) LED “Softwhite” (low S, high L), GE LED “Daylight” (medium S, high L), and a novel “Equal” condition (equal S, M, and L) were used. Refractive error was measured with automated infrared photoretinoscopy (Schaeffel et al., 1987) and ocular components with an ocular biometer (Lenstar LS 900).
Results :
Birds exposed to the “Equal” condition showed a reduction in axial length growth (0.183± 0.029 mm) compared to “Soft” (0.340± 0.028 mm, Cohen’s d= 1.44, t= 3.44, p < 0.001) and “Daylight” (0.377± 0.023 mm, Cohen’s d= 2.01, t= 4.69, p < 0.001). Vitreous chamber depths were also reduced (both p < 0.001). The “Equal” condition showed a greater refractive error shift towards hyperopia (+1.24 ± 0.21D) compared to “Soft” (+0.17± 0.23D, Cohen’s d= 1.47, t= 3.37, and p< 0.001) and “Daylight” (+0.08 ± 0.23D, Cohen’s d= 1.30, t= 3.41, p < 0.001).
Conclusions :
Changes in eye growth and refraction were dependent on the relative S-cone excitation. The spectra of common commercially-available light bulbs stimulated myopic eye growth, while equal cone excitation stimulated hyperopic growth changes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.