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IJ Murray, J Kremers, NR A Parry; Mid-peripheral L and M cone distributions implied from flicker ERGs . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3763.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure L and M cone driven ERGs generated from different regions of the retina and compare these with histological data on cone density distributions. Methods: L, M, and L+M cone driven 30Hz ERGs were measured to a series of stimuli with one of 3 basic configurations: A) Circular stimuli of different angular subtense up to 70° diameter; B) Annuli with 70 deg outer diameter but variable inner diameter; C) Annuli of constant area but increasing eccentricity. Cone contrasts were equalised for each stimulus condition. The modulated and non-modulated regions of the screen had the same mean hue and luminance. Results: The cumulative number of cones in the human retina increases exponentially with stimulus diameter between 0 and 40 degrees eccentricity (Curcio et al.,1990, J. Comp. Neurol. 292: 497-523). The L+M cone ERG amplitude increases with stimulus diameter in direct proportion to the number of cones stimulated. Furthermore, the total L+M responses can be predicted from individual L and M responses by simple linear addition for both the disc and annular stimuli. The ratio of L to M cone driven responses changes systematically with retinal eccentricity, but is different for different subjects. At large eccentricities, the L to M cone ratio decreases, contradicting some genetic studies. Conclusion: The ERG allows us to estimate the relative spatial distribution of L and M cones in the living eye, thereby complementing anatomical studies.
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