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Yasuki Yamauchi, Keisuke Yatsu, James Kuchenbecker, Maureen Neitz, Jay Neitz; L:M Cone Ratio of Japanese Derived with ERG Flicker Photometry Method. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6119.
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© ARVO (1962-2015); The Authors (2016-present)
It is well known that the L/M cone ratio varies widely among humans. In preliminary experiments we found that Asian subjects tended to have smaller L/M cone ratios compared to Caucasian subjects, which led us to predict that there will be significant difference in L/M cone ratio between races. The purpose of this study was to test this prediction, by estimating the L/M cone ratio in Japanese subjects using a newly developed electroretinogram (ERG) flicker photometry method.
L/M cone ratio for each subject was estimated from L- and M- cone spectral sensitivity functions derived from the ERG signal. The peak sensitivity of the L and M cone were obtained from genetic analysis. The subject was asked to observe a flickering stimulus at 30Hz A 530 nm light was used as the reference, while 470, 630 and 650 nm lights were used as the test stimuli. The intensity of the test light was varied until the difference of the ERG response for the reference and test light nulled. Using a simple additive model, we found the weighting factors of the L and M cone spectral sensitivities that gave the best fit of the ERG spectral sensitivity. This weighing factor expresses the L/M cone ratio for the subject.
In our method, the derived L/M ratio is similar to those obtained in our previous method, which used 30 lights of different wavelength. The L/M ratio of the 6 Japanese subjects had a wide distribution, but the average was smaller than that obtained from Caucasian subjects.
Our results indicate that the average L/M cone ratio of Japanese is lower than that of Caucasians. There is a possibility that the low L/M cone ratio is a factor contributing to the high frequency of myopia among Japanese.
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