Binocular Visual Acuity with Combined Correction of Spherical and Longitudinal Chromatic Aberrations

Investigative Ophthalmology & Visual Science
Christina Schwarz; Silvestre Manzanera; Pedro M. Prieto; Pablo Artal

Purpose:A previous study (Artal et al., Optics Express 2010) showed that monocular visual acuity (VA) improved by correcting spherical aberration (SA) and longitudinal chromatic aberration (LCA). However, the effect of their combined correction on binocular visual performance has not been investigated yet. Here, we measured both monocular and binocular VA when correcting SA and LCA separately or in combination.
Methods: We used a binocular adaptive optics visual analyzer to measure binocular and monocular VA at an intermediate contrast of letters (30%). The instrument (Schwarz et al., Optics Letters, 2011) allows for modifying the magnitude and phase of the eye’s complex pupil function. It incorporates two liquid-crystal spatial light modulators for both wavefront shaping and to create the artificial pupil. A micro-display presents letters through the controlled eye’s optics to measure monocular and binocular VA for 4 different cases: 1) natural conditions (LCA and SA present), 2) LCA removed, 3) SA corrected, 4) LCA removed and SA corrected. In the cases where SA is present, the average SA value found in pseudophakic patients was induced (0.149µm for a 4.8mm pupil). LCA was removed by using monochromatic (532nm) instead of polychromatic light. The three subjects that took part in this study had also participated in the previous.
Results: The main tendencies of the previous monocular study were reproduced, although a different instrument was used and the technique to correct for LCA was different. Average monocular VA increased gradually form condition 1) 0.68±0.05; 2) 0.75±0.05; 3) 0.82±0.06 and 4) 1.2±0.2. Average binocular VA for the three subjects increased from 0.80±0.04 for the case when LCA and SA were present to 1.2±0.1 for the case when LCA and SA were corrected. The average binocular summation ratio ranged between 1.0±0.2 and 1.4±0.2, being the smallest in the all-corrected case.
Conclusions: We studied how binocular VA is affected by correcting longitudinal chromatic aberration and spherical aberration in combination. The best performance was attained binocularly when both aberrations were removed. This result may indicates that bilateral implantation of IOLs correcting both SA and LCA could further improve binocular spatial vision.