Abstract
Purpose :
Objective refraction optimizes aspects of image quality, but may do so at the cost of one versus another and thus may not correspond to patients’ perceived optimal visual quality despite improved acuity. The purpose of this study was to determine the relative impact of 3 features (blur, contrast, ghosting) on perceived overall image quality and to evaluate which features were related to measured visual acuity.
Methods :
14 cyclopleged adult observers viewed logMAR acuity charts displayed on an LCD monitor monocularly through a unit magnification telescope with a 3mm aperture. Acuity charts were created from wavefront measures of 30 adult subjects with Down syndrome (DS). For each DS eye, a series of acuity charts were produced to simulate retinal image quality when applying various metric-derived sphero-cylindrical refractions. 10 unique chart sets, comprised of ~65 aberrated and one clear chart, were each viewed by 5 of 14 observers. Observers rated blur, ghosting, and contrast on a 10 point scale (10=poorest), overall image quality on a 0-100 point scale (100=best) and read each chart until 5 total letters were missed (logMAR technique). Multilevel modeling was used to estimate each feature’s influence on overall perceived image quality and letters lost (acuity relative to clear chart).
Results :
Mean clear chart acuity was -0.1±.06 logMAR. Among all charts read with measured acuity < 0.7 logMAR, perceived image quality spanned the entire scale (mean=59±22) and average letters lost was 2 lines (-0.2±.14 logMAR). Perceived blur, ghosting, and contrast were individually correlated with overall perceived image quality and letters lost (p<0.001). In an adjusted analysis for all features, blur, contrast, and ghosting have unique effects on overall perceived image quality (p<0.05) whereas for letters lost, contrast did not exert an effect over and above the other two (p=.8223). Finally, blur (b=-.009, p<0.001) and ghosting (b=-.003, p<0.001) influence letters lost over and beyond their effects on image quality (b=.001,p<.0001).
Conclusions :
Refractions that are objectively identified would ideally have high contrast and low blur and ghosting, but in individuals with elevated aberrations (e.g., individual with DS) compromises may be needed. These data suggest that blur and ghosting may be given priority over contrast when the goal is to improve acuity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.