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Lene Aarvelta Hagen, Solveig Arnegard, Jon V. B. Gjelle, Stuart J. Gilson, James A Kuchenbecker, Maureen Neitz, Jay Neitz, Rigmor C Baraas; Differences in L:M cone ratios obtained with a spatio-chromatic measure and full-field ERG.. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate covariance between the L:M cone ratio obtained with a psychophysical measure of perifoveal single letter acuity with L- and M-cone isolating stimuli, and the L:M cone ratio obtained with full-field ERG.
Fifty-three healthy color normal self-reported Norwegian Caucasians (16–44 yrs; 22 males), were included. All had normal logMAR acuity and no observed ocular abnormalities. Color vision was deemed to be normal when fewer than 3 errors were made on the HRR (4th ed., 2002) and Ishihara pseudo-isochromatic plates (24 pl ed.).Spectral sensitivity functions were measured with full-field ERG in the dominant eye. L- and M-opsin genes were sequenced, and the amino acids specified at spectral tuning sites were used to determine the peak sensitivities for the L- and M-cones. Peak sensitivities were used to calculate the cone ratios. Separately, isolated L-, M-cone and achromatic minimum angle of resolution (MAR) were measured monocularly in the same eye as for ERG with a Sloan E letter at 23% cone contrast and 90% achromatic contrast. Thresholds were measured employing a 4AFC staircase procedure. The mean luminance was 10 cd/m2. The Sloan E was presented at 5 deg eccentricity from a distance of 2.3 m with fixation verified with an eye-tracker. All were corrected to best logMAR acuity.
MAR and ERG L:M ratios ranged between 0.6–3.8 and 0.5–24.0, respectively. There was no correlation between the two measures for the whole group, but a slight correlation for subjects with genes expressing a single L- and M- peak sensitivity (21 of 53) (r2=0.18, p=0.054). There was no correlation, however, between measures of L- and M-cone MAR and L- and M- peak sensitivities, nor ERG %L and L- and M- peak sensitivities. Achromatic, L- and M-cone MAR values (arcmin) ranged between 2.0–4.0, 2.2–7.3 and 2.5–14.5, respectively. The MAR values are within the range of what is expected from estimates of midget cell densities at 5 deg eccentricity [Drasdo et al. (2007) Vis Res 47: 2901–2911].
It appears that when obtaining L:M ratios with spatio-chromatic stimuli in the perifovea, presumably involving chromatic processing, it yields different L:M ratios than those obtained with full-field ERG. This could be down to a change in gain in the retinal circuitry through the chromatic pathway, as suggested for foveal vision [Kremers et al. (2000) JOSA A 17: 517–526], even at this eccentricity.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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