Visual pigment density in single primate foveal cones.

The feasibility is demonstrated of microspectrophotometric studies on primate photoreceptors aligned at right angles to the test beam, rather than axially illuminated. Pigment densities, and hence absorption per unit thickness, are approximately equal in primate rods and foveal cones. These pigment densities are similar to those reported for frog rods and fish cones.