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K.K. Liedel, J.A. Campin, G.H. Pettit; Visual Quality Metrics for Refractive Surgery . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4367.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate potential wavefront–derived metrics to provide a better means of assessing visual quality. Methods: Human data was obtained from 366 eyes enrolled in LASIK clinical trials. This population included both myopic and hyperopic eyes treated either with conventional or wavefront–guided surgery. Exam data including wavefront measurements and mesopic visual acuity measures were obtained at the 3–month post–op visit. A computer program processed the wavefront data and calculated retinal plane parameters (PSF, MTF, and PTF), as well as numerous single value metrics. The software analysis was performed over different pupil diameters and with configurable neural threshold and simulated Stiles–Crawford effects. The measured vision performance parameters were compared to simple RMS error as well as the calculated metrics under various simulation conditions. Results: Tested metrics included both novel and previously published parameters (e.g., Strehl ratio, PSF peak, MTF volume, etc.). Low contrast cycloplegic uncorrected visual acuity (lccUCVA) was typically better correlated to wavefront metrics than were other tested acuities. Looking at the optimal wavefront diameter, best correlation between lccUCVA and most of the metrics was observed for pupil diameters between 4.5 and 5.0 mm. For RMS error the peak correlation coefficient was 0.74. Better correlation was seen with several of the calculated metrics. In some instances including a simulated neural threshold effect improved correlation still further. Correlation between lccUCVA and post–neural PSF entropy was 0.79. Including a simulated Stiles–Crawford effect (as opposed to simply constraining the wavefront analysis diameter) did not significantly improve metric correlations to lccUCVA unless the radial apodization factor was assumed to be significantly larger than values reported in the literature. Conclusions: Several of the metrics evaluated exceed the correlations established with wavefront RMS and other known metrics published to date. With refinement these parameters should yield useful information regarding vision quality and calculation of the effective clinical refraction.
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