Abstract
Purpose :
Spatial, temporal, and spectral characteristics of visual stimulation are known to influence emmetropization in the chick. Previous research (Hess et al., 2008) has suggested that the high spatial frequency information in static noise stimuli can act to slow eye growth and reduce the development of myopia. In this experiment, we tested whether high spatial frequency information has the same effect when the noise stimulus is dynamic and whether the spectral content of the stimulus is relevant in controlling eye growth.
Methods :
66 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 three stimulus conditions were i) Control: a steady full-screen of average luminance (110 cd/m2), ii) Flicker: full-screen sinusoidal flicker (frequency 10Hz, Michelson Contrast 0.82, RMS Contrast 0.56) iii) Noise: a dynamic full-screen noise stimulus (peak temporal frequency 10Hz; RMS contrast 0.56). Two spectral conditions, White and Yellow, were used for six conditions total. The White spectral condition used the red, green, and blue monitor components while the Yellow condition used only the red and green components. The average luminance for all stimulus conditions was equated. Ocular biometry (Lenstar LS 900) and refraction (Hartinger Coincidence Refractometer) were measured before and after three days of stimulus exposure.
Results :
Eye growth showed a main effect of stimulus (F=6.58 , p < 0.01) and an interaction between stimulus and the spectral characteristics (F=11.58, p < 0.001). 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). Birds exposed to White Noise showed more eye growth than those in the White Control condition (0.036 mm/day, p < 0.05). There was no difference in eye growth among the birds exposed to the stimulus conditions with Yellow light.
Conclusions :
Consistent with previous research, broad-spectrum high-frequency flicker produced shorter, less myopic eyes than a steady light. Inconsistent with previous research using static noise, broad spectrum dynamic noise patterns produced longer eyes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.