Abstract
Previous research (Hess et al., 2008) suggested that high spatial frequency information in static noise reduces development of myopia. We tested whether a high frequency dynamic noise stimulus would also slow myopic eye growth in white and yellow light.
118 one-week old chicks were exposed to stimuli presented on a computer monitor (12h light/dark cycle) for three days. All stimulus conditions had a mean luminance of 110 cd/m2 and a frequency of 0, 0.2 or 10 Hz with RMS 0.56: i) Flicker: full-screen sinusoidal flicker, ii) Noise: a dynamic full-screen noise, iii) Control: a steady full-screen. Conditions were presented in White or Yellow light. Ocular biometry and refraction were measured before and after three days of stimulus exposure.
Eye growth showed a main effect of stimulus (F=5.275, p < 0.01) and an interaction between stimulus and the spectral characteristics (F = 6.245, p < 0.01). Frequency did not interact with the other variables or show a main effect. Birds exposed to White Noise showed more eye growth than those in the White Control condition (0.036 mm/day, p < 0.05). Birds exposed to 10Hz White Flicker showed less eye growth than birds under the White Control (−0.03 mm/day, p < 0.05) or White Noise condition (−0.06 mm/day, p < 0.001). This difference was not seen in Yellow light.
Inconsistent with previous research, broad-spectrum dynamic noise produced longer eyes at both 10Hz and 0.2Hz. The data are consistent with the idea that unreliable, spatially local short-wavelength spatial contrast induces the eye to grow.