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A. Ho, S. M. Delgado, A. Martinez, P. Sankaridurg; Change in Asymmetry of Peripheral Refraction With Accommodation: Myopes versus Emmetropes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):806.
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© ARVO (1962-2015); The Authors (2016-present)
We investigated the change in asymmetry in peripheral refraction RPR with accommodation, especially the differences between myopes and emmetropes, as both of these factors have been postulated to be relevant to myopia progression.
Emmetropes (n=20, +0.625 to-0.375D) and myopes (n=20, -0.50D to -3.875D) aged 18 to 35 yr were enrolled for this study. Single-vision AirOptixTM soft contact lenses were used to correct distance central refractive state in all subjects during measurements. A modified Shin-Nippon Nvision-K5001 autorefractor was used to measure refraction at central and 20°, 30° and 40° nasal and temporal field (presented randomly) and at target distances of 2 m, 40 cm, 30 cm and 21 cm (counterbalanced presentation sequence). All measurements were the mean of five repeats. RPR were calculated as the difference in mean sphere (M) between a given peripheral refraction and the central refraction at the same target distance. For each subject and accommodative distance, the set of RPR across all peripheral angles were fitted to a 2nd-order polynomial. Asymmetry and curvature of RPR were defined as the 2nd-order and 1st-order coefficients respectively.
Multi-way ANOVA was used to analyse the data. Both emmetropes (-1.58 ± 0.14 deg-2×10-4) and myopes (-1.48 ± 0.20 deg-2×10-4) showed small but significant change (p<0.001) in curvature of RPR (more myopic) with accommodation. The change in curvature with accommodation was not different between emmetropes and myopes (p=0.70). Only emmetropes showed a significant change (emmetropes = -1.45 ± 0.31 deg-1×10-3, p<0.001, myopes = 0.31 ± 0.36 deg-1×10-3, p=0.40) in asymmetry of RPR with accommodation. The change in asymmetry with accommodation was statistically significantly different between emmetropes and myopes (p<0.001).
These results suggest a lenticular or accommodative component in the differences between emmetropic and myopic eyes.
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