THE EFFECT OF AN INTERRUPTED DAILY PERIOD OF NORMAL VISUAL-STIMULATION ON FORM DEPRIVATION MYOPIA IN CHICKS

The aim of this study was to determine whether an integrator of neural activity influences the amount of myopia and axial elongation resulti ng from deprivation of form vision. The effects on ocular parameters o f a continuous period of 30 min per day of normal vision was compared to two exposures of 15 min duration each, or three exposures of 10 min each. For the remaining time, chicks had monocular translucent occlus ion in a 12 hr light/12 hr dark diurnal cycle, for either 2 or 3 weeks . Fellow eyes and the eyes of bilaterally unoccluded chicks were used as controls. We found that several short periods of normal visual stim ulation per day were more effective in preventing the development of f orm deprivation myopia and axial elongation than was one single period of the same total duration, after both 2 and 3 weeks of treatment. Th is study suggests that the level of neural activity in the retina may have a cumulative effect in influencing ocular growth. (C) 1997 Elsevi er Science Ltd.