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Kai L. Yew, Sabrina Chan, Christine F. Wildsoet; Negative 30 D lenses behave like occluders in inducing myopia in young chicks. Journal of Vision 2002;2(10):43. doi: 10.1167/2.10.43.
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© ARVO (1962-2015); The Authors (2016-present)
PURPOSE: Form deprivation (FD; e.g. with diffusers), produces exaggerated axial eye growth and myopia, as do negative lenses. The response to low-powered lenses is compensatory, increasing in proportion to the defocus imposed. Previous studies suggest that these lens and FD effects involve different mechanisms. Here, we investigated whether high powered negative power lenses induce myopia, at least partly by FD.
METHODS: Three treatments were used: − 5 D and − 30 D lenses, and opaque white occluders. They were monocularly applied to 4-day-old chicks, and worn for 2 weeks (n ≥ 6 per group). Refractive errors (RE) were measured by photoretinoscopy; axial ocular dimensions were recorded by high frequency A-scan ultrasonography under anesthesia.
RESULTS: Excess axial eye growth and myopia were found in all 3 groups. The responses to the −30 D lens and occluder were very similar at all time points while the response to the −5 D lens was consistently smaller. The vitreous chamber depth (VCD) accounted for most of the axial changes. Significant differences exist between the responses to −5 D lens versus the −30 D lens and occluder (Tukey's test, p < 0.005). The mean interocular difference data were:
Time − 5 D lens − 30 D lens Occluder
Day 4 RE (D) =t- 5.00±0.36 − 11.13±1.34 − 10.64±1.74
Day 11 RE (D) − 4.56±1.30 − 9.25±0.74 − 11.49±1.84
Overall rates of VCD change (mm day-1) 0.027±0.005 0.097±0.039 0.099±0.04
CONCLUSION: Our data show that the −30 D lens and occluder had similar effects that were greater than the effect of the −5 D lens. These results suggest that the −30 D lens and occluder activate the same mechanism, in contrast to the conclusions of others that negative lenses and diffusers stimulate different mechanisms.
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