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Myoung Joon Kim, Len Zheleznyak, Ramkumar Sabesan, Scott MacRae, Geunyoung Yoon; Improving Through-Focus Visual Performance Using Primary And Secondary Spherical Aberrations. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6332.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate relative contribution of Zernike primary and secondary spherical aberration (SA) to through-focus visual performance.
A theoretical simulation was conducted using correlation coefficient of convolved images as a retinal image quality (RIQ) metric. Through-focus RIQ was obtained with various combinations of Zernike primary and secondary SAs of different signs and magnitudes. The peak of through-focus RIQ was shifted to distance (0D defocus) and the area under RIQ between 0 and 2.5D was calculated. We then determined the values of SAs that maximize the area RIQ under each of the three conditions, (1) primary SA alone, (2) secondary SA alone and (3) both primary and secondary SAs. Through-focus visual performance under these conditions was evaluated by measuring through-focus high contrast visual acuity with a 4mm pupil in 2 cyclopleged subjects. An adaptive optics vision simulator was used to correct the subjects’ native aberrations and to induce SAs.
In a theoretical simulation with exclusively primary or secondary SA, the best average RIQ was obtained when primary and secondary SA were positive; specifically +0.275µm and +0.2µm, respectively. When primary (+0.10µm) and secondary SAs (+0.15µm) were combined, the simulation showed improved average RIQ. Overall, primary SA interacting with positive secondary SA provides better average RIQ than with negative secondary SA. The interaction between primary and secondary SAs to maximize through-focus RIQ between 0 and 2.5D was expressed by the linear equation, secondary SA = 0.4 x primary SA + 0.15. A combination of the two SAs above/below the equation line optimizes near/intermediate visual quality, respectively. Combining primary and secondary SA showed a benefit in average VA between 0 and 2D (-0.12+0.04logMAR) compared to primary only or secondary only SA (0.00+0.17 and -0.04+0.09logMAR, respectively).
Relative magnitudes of primary and secondary SA determine optimal object distances which receive an improvement in visual quality. Interactions of primary and secondary SA can further improve through-focus RIQ compared to individual SAs alone, resulting in improved multifocal ophthalmic lens designs for presbyopia.
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