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G. Dai, K.–M.A. Tuan; Correlation of Optical Metrics to Visual Performance: . Invest. Ophthalmol. Vis. Sci. 2004;45(13):201.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Myopic eyes which received LASIK treatments were studied to determine the correlation of optical metrics to visual performance. The optical metrics included root mean squares (RMS) error, modulation transfer function (MTF), encircled energy (EE), and Strehl ratio. The impact of high order aberrations (represented by Zernike polynomials) on visual performance was also examined. Methods: A polychromatic point spread function model with chromatic aberrations, Stiles–Crawford effect, and retinal spectral response was used to calculate MTF. One hundred and sixty–six myopic patients received wavefront–driven LASIK procedures. Three hundred nine wavefront exams were conducted pre–operatively; 239 exams were given 1 month post–op; 252 exams at 3 months post–op; and 67 exams at 6 months post–op. Various optical metrics were calculated from the exam data. Multiple regression analysis was used to examine the correlation to visual performance in terms of uncorrected visual acuity and contrast sensitivity. Results: Among the various optical metrics, EE and RMS error had the highest correlation with uncorrected visual acuity. Multiple regression analysis indicates that combining some of the optical metrics results in an even higher correlation. Simulation of individual Zernike terms showed that symmetrical terms have a higher impact on visual performance than asymmetrical terms. Conclusions: Multiple regressions show that the best correlation to visual acuity is achieved by combining EE and RMS. Symmetrical aberrations have a stronger impact on visual performance than asymmetrical aberrations.
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