Abstract
Purpose :
The differential responses of S, M, and L cones to short, medium, and long wavelengths of light produce human color vision. Objective methods have been developed to examine cone spectral responses but remain limited. Previously, we developed an adaptive optics optical coherence tomography (AO-OCT) method that used the cone optoretinogram to identify spectral types of individual human cones with unprecedented sensitivity, accuracy, and efficiency [1]. Here, we extend this approach to measuring cone sensitivities across the visible spectrum by controlling the wavelength and strength of stimulation with a supercontinuum laser.
Methods :
AO-OCT volumes of 1°×0.8° at 3.8° temporal retina were acquired repeatedly over 5s at 10 Hz for one color normal subject. AO-OCT cone optoretinograms were observed 2.5s after stimulation with flashes of 450, 480, 520, 545, 570, 600, and 635 nm light. Flashes consisting of 5-8 power levels (0.23-31μW) were generated by a supercontinuum laser and controlled by an acousto-optic tunable filter, both spectrally (<1.8 nm bandwidth) and temporally (60 ms flash duration except at 450 and 480 nm that needed longer exposures). Cone spectral types were classified and the mean cone response following stimulus was obtained for the different flash strengths and wavelengths. After compensating for lenticular and macular absorption, the mean cone response as a function of flash strength was fit to a power law from which cone spectral sensitivities were extracted.
Results :
Twenty spectral sensitivity measurements were acquired in total. We compared our measurements to Stockman & Sharpe’s well-recognized psychophysical cone fundamentals using an iterative function to find the offset producing the minimum total difference between our sensitivity measurements and that of the normalized psychophysical data. Our measurements produced a least-squared error for S, M, and L cones of 0.00, 0.017, and 0.022, respectively, using all seven wavelengths with the exception of 480 nm for S cones. To date we have determined confidence intervals (CIs) for L and M cones of <0.083 and <0.074, respectively, for 545, 570, and 600 nm and for L cones of ±0.034 at 635 nm.
Conclusions :
We have developed an objective method that provides highly specific and sensitive measurements of cone sensitivity across the visible spectrum.
[1] Zhang, et al. PNAS 2019 116 (16) 7951-6
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.