A bipartite field (retinal irradiance ratio 2:1 on the two sides) was imaged on the retina of an albino rat. Following exposure to the visual stimulus, the retina was dissected from the eye and placed in an incubation medium which selectively stains the ellipsoid portion of photoreceptors which have been exposed to light. In this study, the optical density of stain was measured as a function of stimulus magnitude. It was shown that the density of stain increased with increasing retinal irradiance over the range of values tested. The indicator system tended to underestimate differences in stimulus magnitude, and showed evidence of approaching an asymptote at higher stimulus levels. Many technical problems encountered in this experiment made this a difficult exercise.
JAY M. ENOCH, "Validation of an Indicator of Mammalian Retinal Receptor Response: Density of Stain as a Function of Stimulus Magnitude," J. Opt. Soc. Am. 56, 116-123 (1966)