Red/green sensitivity in normal vision

Abstract

Red/green sensitivity was measured in 197 normal subjects by two different methods. In the first a fixed yellow light ( λ=590 mμ) was matched by a mixture of red and green in an anomaloscope and the red/green ratio found. This depends upon the nature of the red and green cone pigments but not upon the amount of each present. In the second test the brightness of a green light was equated to that of a fixed red light by flicker photometry. This might be expected to depend upon the relative amounts of red and green cone pigments as well as upon their nature. To learn whether relative red/green brightness did depend upon the relative amounts of red/green-sensitive pigments on the fovea, these were measured by retinal densitometry in some twenty subjects who were specially red-sensitive or green-sensitive by flicker measurements. With one exception all those who were red-sensitive had a high red/green pigment ratio; all who were green-sensitive a low red/green pigment ratio. The variations in flicker settings in our population show a standard deviation about four times that of the anomaloscope settings, and there was little association between the two.