Purchase this article with an account.
Jens Buehren, Hendrik Jungnickel, Wolfgang Raab, Daniel Weigel, Michael Gebhardt, Richard Kowarschik, Thomas Kohnen; Influence of aberration-induced blur on contrast sensitivity: comparison of different optotype sizes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1280.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To compare the decrease of contrast sensitivity (CS) due to defocus and higher-order aberration (HOA) blur measured with optotypes of different size.
Thirty-three emmetropic healty volunteers were included. In a first experiment (defocus blur), CS was measured in 31 eyes. Experimental fogging was performed with spherical trial lenses of 0, +0.25, +0.5 and +0.75 diopters (D). In a second experiment (HOA blur), CS was measured in 3 eyes at an adaptive optics (AO) visual simulator. Besides the correction of lower-order aberrations (LOA) and full correction, subjects were presented 6 wavefront errors of different blur strength and characteristics (3 keratoconus eyes, 3 post-LASIK eyes). In total, 8 different wavefront errors with a VSOTF (visual Strehl ratio based on the optical transfer function) range of -0.05 to -1.70 log units were presented. In both experiments, CS was measured with Landolt rings of 1.3 and 0.3 logMAR using FrACT software. The impact of defocus blur (D) or HOA blur (VSOTF) on CS was assessed using linear regression analysis. The regression coefficient b and the coefficient of determination R2 reflect the sensitivity of the CS contrast test to aberration-induced blur.
Experiment 1: Unfogged photopic CS was 1.93±0.06 logCS (1.3 logMAR) and 1.56±0.05 logCS (0.3 logMAR). Regression coefficients were higher for the 0.3 logMAR (b=-0.88, R2=0.70) than for the 1.3 logMAR Landolt ring (b=-0.39, R2=0.28). Experiment 2: CS was 1.98±0.17 (0.3 logMAR optotype: 0.95±0.14) log units with full AO correction. Also in this experiment, CS was more sensitive to optical blur if measured Landolt rings of 0.3 logMAR (b=0.63, R2=0.74) compared to those of 1.3 logMAR (b=0.34, R2=0.34).
CS tests with large optotypes such as the Pelli-Robson test may not pick up subtle, yet notable aberration-induced changes in retinal image quality. Therefore, for the assessment of effects of optical aberrations, CS testing should be performed at higher spatial frequencies (e.g., 0.3 logMAR Landolt ring).
This PDF is available to Subscribers Only