Theoretical Impact of Chromatic Aberration Correction on Visual Acuity

Abstract

Purpose : The purpose of this project was to characterize the theoretical impact of chromatic aberration correction on foveal visual acuity (VA).

Methods : Modelling tools were developed that enable simulations of the optical impact of physiologically relevant amounts of chromatic aberration in real human eyes and computation of VA of an ideal observer. A total of 882 polychromatic eye models were generated leveraging foveal monochromatic wavefronts and longitudinal chromatic aberration (LCA) and transverse chromatic aberration (TCA) measurements from the literature to bound and define the model eye parameters. Performance simulations were performed using ISETBio. Low contrast (20%) VA was computed for both low (4 cd/m²) and high (160 cd/m²) luminance conditions. Acuity experiments were simulated using the Poisson-noise-limited ideal-observer model for a four alternative forced choice tumbling-E task. The impact of LCA and TCA correction on VA, and the impact of monochromatic Strehl ratio on VA improvements due to LCA and TCA correction were characterized.

Results : Generally, the trends and effect magnitudes regarding the impact of LCA and TCA are quite similar when comparing high and low luminance. Simulations indicate an improvement in ideal-observer VA when LCA is corrected. Improvements in VA are greater in simulated subjects with less monochromatic aberrations and with less foveal TCA. With TCA of 0.4 arcmin and LCA of 2.2 D (nominally population average), VA improved by -0.04 to -0.16 logMAR. Improvements in VA appear to be (mostly) linear with respect to the magnitude of LCA. Simulations indicate modest changes in VA when TCA is corrected. Improvements in VA are manifest when large amounts of TCA are present, and when LCA is fully corrected, but in the known physiological range, changes in VA with TCA correction are negligible. With TCA of 2.76 arcmin (between the population mean and maximum) and LCA of 2.2D, VA improved by 0 to -0.04 logMAR.

Conclusions : Simulations indicate that correction of chromatic aberrations can improve ideal-observer VA significantly, and thus such improvements might be expected for real observers. However, more of an improvement in VA is expected with LCA correction than with TCA correction, and the magnitude of the improvement in VA is greater for subjects with less monochromatic aberrations.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.