VARIATIONS IN CONE POPULATIONS FOR RED-GREEN COLOR-VISION EXAMINED BYANALYSIS OF MESSENGER-RNA

IN the central human retina, there are estimated to be nearly two L co ne photoreceptors for each M cone. The extent to which this value vari es across individuals is unclear and little is known about how the M:L cone ratio might change with retinal location. To address these quest ions, the ratio of M:L cone pigment mRNA was examined at different loc ations. For patches of central retina, the average M:L ratio was about 2:3 which decreased to about 1:3 for patches 40 degrees eccentric. Th ere were also large individual differences among the 23 eyes examined. The extremes differed in central M:L mRNA ratio by a factor of > 3. T he measured differences in mRNA ratio are proposed to reflect differen ces in photoreceptor ratio. Such variations provide unique opportuniti es for understanding how the neural circuitry for color vision is affe cted by changes in cone ratio. (C) 1998 Rapid Science Ltd.