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SARA AISSATI, Palash Bharadwaj, Emily Slezak, Xiaoyun Jiang, Sierra Schleufer, Susana Marcos, Ramkumar Sabesan; Investigating the factors limiting visual acuity at different wavelengths.. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2561 – F0515.
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© ARVO (1962-2015); The Authors (2016-present)
Visual performance across the visible spectrum is limited by many factors, including monochromatic & chromatic aberrations,differences in spectral sensitivity across cone types, and post-receptoral processing of spatial & chromatic contrast.We sought to investigate the interplay between these factors using a combination of adaptive optics(AO) psychophysics & computational modeling
Four cyclopleged subjects were measured in a tumbling ‘E-letter’ visual acuity(VA)4AFC experiment under dynamic AO correction.The visual display consisted of a digital micromirror device (DMD) & two LEDs 427±13nm & 630±16nm(luminance for both=5.7cd/m2).Subjects set subjectively the best focus at each tested wavelength.VA was measured under 4 different stimulus conditions with variations in spatial & chromatic contrast: black ‘E’ on either a blue and red background (BKG); red ‘E’ on blue BKG and blue 'E' on red BKG.These conditions were also simulated using ISETBio(Image Systems Engineering Toolbox for Biology)computational pipeline.The simulations incorporated the effects of the calibrated display,human eye’s optics,absorption by the anterior segment of the eye,macular pigment & cone photoisomerizations.To verify the relative contributions of spatial(L+M modulation) & chromatic(L-M modulation) contrast to the visual task, these were calculated from the resultant cone photoisomerizations
VA improved as expected in all conditions after correcting HOAs.The mean LogMAR VA with AO was -0.20±0.04 & -0.06±0.02 for monochromatic red and blue BKG respectively.The mean VA with AO was -0.17±0.05 & 0.03±0.02 for polychromatic targets(red ‘E’ on blue BKG,and vice-versa respectively).The improvement was typically lower for blue letters (11%) compared to red (16%).Simulations verified that once optical aberrations are removed with AO,VA was better under conditions where both spatial & chromatic contrast were high,i.e.the red letters.Conversely,VA was poorer when either of the contrasts were low, for eg.,the monochromatic blue target where the spatial and the chromatic contrast were high(>95%) & low(<10%) respectively
A combination of AO psychophysics experiments and ISETBio simulations enabled us to understand the factors limiting VA at different wavelengths.Similar experimental & modeling platforms,paired with ideal observer analysis,may give insights on the optical,retinal & neural limitations to spatial & chromatic vision
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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