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R. Sabesan, G. Yoon; Role of Native Spherical Aberration in the Extended Depth of Focus. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6345.
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The purpose of this study is to investigate how long-term visual experience with one’s own native spherical aberration (SA) influences the depth of focus with induced SA.
Through focus high contrast visual acuity was measured after correcting all aberrations and imposing each of +0.5µm and -0.5µm SA for a 6 mm pupil using an adaptive optics system. Six cyclopleged normal eyes (mean age in years: 49.5 ± 6.5) with different magnitudes of positive native SA were enrolled in this study. The induction of SA was maintained in real time during the visual acuity measurements. The focus position for distance vision was first optimized at which visual acuity was best. Depth of focus was determined as the near dioptric range from the best focus for which visual acuity was better than 0.3logMAR corresponding to 20/40 Snellen acuity.
The mean native SA of subjects for a 6 mm pupil was 0.40 ± 0.24 µm (range: 0.17-0.8 µm). Correction of aberrations and induction of SA were performed reliably with adaptive optics with a residual error below 0.08 µm in all cases. The average depth of focus (2.14 ± 0.33D) with positive SA was larger than that (1.86 ± 0.30D) with negative SA, the difference between the two ranging from 0.35D to -0.04D. The difference in depth of focus between positive and negative SA was observed to obey a quadratic (R2 = 0.98) relation with the native SA of subjects. This difference tended to be significantly higher when subject’s native SA was closer to the induced SA and the maximum difference was observed when the native SA was equal to the induced positive SA of +0.5 µm.
The magnitude of native SA has a significant influence on the depth of focus extended by artificially induced SA. This might be attributed to neural adaptation to one’s own native SA.
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