Abstract
Purpose: :
Previous studies have concluded that the packing arrangement of L and M cones near the center of the human fovea is not distinguishable from random in most eyes. We sought to determine whether this is also true for extrafoveal retina.
Methods: :
We classified the L, M, and S cones in one female color-normal subject with adaptive optics imaging combined with retinal densitometry at 1.25 , 4, and 10 deg in the temporal retina. We evaluated the packing arrangement of the 3 cone classes by comparing the frequencies of distances between all cones of the same type with those expected based on a random pigment assignment rule.
Results: :
314 cones were classified at 10 deg, 739 at 4 deg, and 1456 at 1.25 deg. The number of misidentified L and M cones at each location was estimated at 3.9 %, 2.8 %, and 2.5 % respectively. Though the ratio of L to M cones did not differ significantly across the eccentricities tested, peripheral L and M cones exhibited significant clumping whereas those at 1.25 deg did not.
Conclusions: :
The organization of L and M cones outside the fovea, at least in one subject, shows a clear tendency toward clumping of cones of like type. This clumping may have implications for the strength of red-green color vision in peripheral retina since it increases the probability that peripheral midget cell centers will be driven by predominantly one class of cone.
Keywords: retina • color vision • receptors