Purchase this article with an account.
C.M. Liu, D. Rushforth, R.M. Douglas, K.L. Schmid, W.K. Stell; Lack of Spatial-Frequency Dependency of Myopia-Prevention by Computer-Generated Sine-Wave Gratings in Chicks . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1980.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Ocular growth is regulated by visual feedback mechanisms in the retina. Depriving the eye of high-quality vision results in form-deprivation myopia (FDM), which can be prevented by diffuser removal for ≤ 3 hr/da (Napper et al., 1997). Panoramic vertical sine-wave gratings printed on a rotating drum, viewed for 20 min/da, inhibit FDM optimally at ~1 cyc/deg but less at other frequencies (Schmid & Wildsoet, 1997). Here we tested whether computer-generated gratings have the same effect. Methods: Sine-wave gratings were displayed on a pair of video monitors, each aligned with the visual axis of one eye of a chick restrained without anesthesia 30 cm away. Mean luminance was 2-8 cd/m2 (equivalent illuminance ~15-60 lux) and Michaelson contrast was 85%. The screens subtended ~30 deg horizontally and were surrounded by black borders and shielding. One eye was form-deprived with a goggle at P7. For the next 4-5 days the chick was ungoggled for 1 hr/da at randomly chosen times between 10:00 am and 4:00 pm and treated as follows: (1) goggle on, stay in cage; (2) goggle off, stay in cage; (3) goggle off, 1 hr of video stimulation (0 [uniform grey], 0.1, 1.0 or 5.0 cyc/deg grating, all of the same mean luminance), then back to cage. One day after the last treatment all eyes were refracted and measured. Results: Goggling for 12 hr induced a myopic refractive error (-13.5±0.82 D goggled vs -2.0±1.8 D goggle-free [interocular difference, (goggled-open)], mean±SD) and increases in vitreal chamber depth (0.62±0.12 vs 0.27±0.11 mm) and anterior chamber depth (0.25±0.13 vs 0.01±0.10 mm) (Tukey test: all P<0.0005). Unrestricted vision in the cage, gratings at all spatial frequencies, and uniform grey reduced to a similar degree the effects of FD on refractive error (e.g.: -7.5±2.2 D @1.0 cyc/deg vs -8.5±0.5 D @0 cyc/deg), vitreal chamber depth (0.15±0.12 mm @1.0 cyc/deg vs 0.20±0.04 mm @0 cyc/deg) and anterior chamber depth (0.03±0.07 mm @1.0 cyc/deg vs 0.06±0.02 mm @0 cyc/deg)(all P>>0.05). Conclusions: The lack of dependence of FDM-prevention on grating frequency was unexpected. Activation of myopia-preventing mechanisms by light alone, independent of texture, is unlikely since ample light intensity without texture (FD) causes myopia. Therefore, under conditions of our experiments myopia may be prevented by very low and very high spatial frequencies (lighted screen surrounded by a dark border, approximating a square-wave grating), or by ON-OFF effects due to scanning of gaze across the light-dark border.
This PDF is available to Subscribers Only