Figure 2. Distribution of cones and opsin expression in mouse and human retina.

A. In the mouse, cones are scattered throughout the retina, with M-cones (green) predominating in the dorsal retina and S-cones (blue) predominating in the ventral retina. Many cones express both opsins. B. M-opsin and S-opsin are expressed in complementary dorsal (D) to ventral (V) gradients across the mouse retina, likely in response to a gradient of thyroid hormone (TH), which is established between P4 and P10, and is highest in the dorsal retina as indicated. C. This graph shows the spatial density of rods (blue) and cones (orange) in a horizontal strip of human retina across the fovea (centered at position 0) and optic disc. Cones are concentrated in the fovea, and rods are excluded from this region. Elsewhere in the retina, rods predominate and cones are sparse. D. Within the fovea, cones expressing either green or red opsin predominate, with cones expression blue opsin found sparsely around the peripheral fovea region. Human cones only express a single type of opsin.

Panels A and B are from (Applebury et al., 2000), reprinted by permission from Cell Press, with TH gradient added from (Roberts et al., 2006). Panel C is from (Rodieck, 1998), pg. 43, reprinted by permission from Sinauer Associates, Inc. Panel D is from (Cepko, 2000), Figure 2, reprinted by permission from Macmillan Publishers, Ltd: Nature 24: 99−100, copyright 2000.