Abstract
Purpose :
Our previous work showed that the eyes of birds that viewed gray-scale dynamic noise patterns grew longer which resulted in increased myopia (Taylor et al., 2017 ). Gray-scale dynamic visual noise produces a random luminance signal on the retina. We hypothesized that randomizing the color signal, in addition to the luminance signal, would increase eye-growth beyond that observed with gray-scale noise.
Methods :
24 one-week old chicks were exposed to visual stimulation presented during a 12h light/dark cycle for three days. An Eizo computer monitor placed outside a Plexiglas cage was used to present the stimuli. The two stimulus conditions were i) gray-scale noise: a dynamic noise with no color variation ii) RGB noise: noise with the same, average luminance, contrast, spatial and temporal characteristics as gray-scale noise but with randomized red, green, and blue stimulation. Both stimuli were presented at 110 cd/m2 with a peak temporal frequency of 10 Hz, peak spatial frequency 1.6 cycles/degree, and an RMS contrast of 0.56. Ocular biometry (Lenstar LS 900) and refraction (Schaeffel et al., 1993) were measured before and after stimulus exposure. Mean changes and standard error in growth and refractive error were calculated, one-sided t-tests performed, and effect sizes (Cohen’s d) computed.
Results :
Birds exposed to RGB noise showed increased eye growth (0.143 ± 0.013 versus 0.122 ± 0.015 mm/day, p < .05, t = 1.97, d = 0.82) and refractive error (-0.386 ± 0.086 versus -0.09 ± 0.097 D/day, p < .01, t = 3.5, d=1.48) over those birds exposed to gray-scale noise. Eye growth in the gray-scale noise condition in this experiment (0.122 ± 0.015 mm/day) replicated those in an identical condition presented in Taylor et al., 2017 (0.135 ± 0.058 mm/day).
Conclusions :
The emmetropization system is further disrupted when randomized color information is combined with randomized luminance information. These results emphasize the importance of predictable color and luminance cues in guiding emmetropization and imply that exposure to environments that contain a low visual signal to noise ratio may induce myopia.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.