Abstract
Purpose: :
To determine if change in logMAR visual acuity (VA) is highly correlated with change in key image quality (IQ) metrics in both normal and highly aberrated eyes.
Methods: :
15 normal, best corrected wavefront errors (WFEs) were randomly selected from the Thibos et al (J Opt Soc Amer A 19, 2329-48; 2002) 100 normal eye data set and 7 keratoconic (KC) WFEs from the Marsack et al data set (Optom Vis Sci 2007;84: 463-470). All WFEs were rescaled to a 4mm pupil. These 22 WFEs were scaled in magnitude up and down to yield 12 levels of WFE and in turn to calculate 30 IQ metrics. The wavefront error of 2 normal subjects was measured through their best corrections. For each subject, for each of the 264 WFEs, 3 unique acuity charts of 30% contrast were simulated after pre-compensating for the measured residual aberrations over a 3mm pupil, yielding 792 (22 * 12 * 3) unique logMAR chart simulations for each subject. For each chart, VA was measured on the 2 subjects up to the 5th letter missed through a 3mm pupil placed conjugate with the subject’s dilated pupil. VA was recorded as the change in VA (VA for test chart of interest - average VA obtained on 3 unaberrated charts). The resulting ΔVA was linearly regressed against change in each of the 30 IQ metrics in normal and KC eyes separately and in combination.
Conclusions: :
Change in logMAR acuity is highly correlated (R2 greater than 0.75) with change in 3 log IQ metrics (neural strength, visual Strehl, light in the bucket) regardless of whether the eye is normal or highly aberrated supporting each IQ metric's role as a viable objective surrogate for visual acuity.
Keywords: visual acuity • aberrations • keratoconus