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Xiaoyun Jiang, James Kuchenbecker, Zhaojie Yao, Ramkumar Sabesan; Longitudinal Chromatic Aberration(LCA) compensation for adaptive optics vision testing and imaging. Invest. Ophthalmol. Vis. Sci. 2018;59(9):655.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular longitudinal chromatic aberration(LCA) impedes vision testing and high-resolution imaging with multiple wavelengths simultaneously. Adaptive optics(AO) vision simulation(AOSIM) systems (with no imaging) and AO scanning laser ophthalmoscopes(AOSLOs) typically use the average population vergence between different wavelengths to compensate LCA. Here, we explore the feasibility of a badal system based on wavelength-selective filters for individualized LCA correction in both AOSIM and AOSLO platforms.
A Badal optometer consisting of two mirrors on a translation stage was placed between the focusing elements of a telescope in an AOSIM and an AOSLO. A pair of long-pass filters with 600nm(AOSIM) and 685nm(AOSLO) cut-off wavelengths were placed statically in the same telescope. Altering the distance dynamically between the mirrors and the filters introduced defocus in the transmitted wavefront sensing/longer wavelengths relative to the reflected shorter wavelength, thus offering customizable LCA compensation between the two channels.The AOSIM used 900nm for wavefront sensing, custom LED illumination(centered at 526nm and 661nm) and DMD display for vision testing. Luminance contrast sensitivity functions(CSF) were measured serially for 526 and 661nm using the quick CSF method over a 6mm AO-corrected pupil. In the AOSLO, a supercontinuum source provided multi-wavelength illumination(543nm, 578nm and 840nm for retinal imaging,900nm for wavefront sensing). All wavelengths had zero vergence at each pupil plane, except at the eye’s pupil where LCA was individually compensated. AOSLO images were obtained in all imaging channels at the fovea, 0.5 and 1deg temporal eccentricity.
The individual luminance AO-corrected CSFs at 526nm and 661nm aligned with each other after LCA correction and had no significant differences. The cut-off spatial frequency was ~30cyc/deg. AOSLO imaging power at the eye were: 3.7μW for 543nm, 4.4μW for 578nm and 62.3μW for 840nm. Images obtained by registering 3-10 second LCA corrected videos showed good correlation and comparable resolution compared to images obtained without the Badal system, but by introducing population average LCA at the entrance pupil.
Individualized LCA compensation is demonstrated for vision testing systems enabling high-resolution, multi-wavelength imaging and stimulation across a range of human subjects.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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