• Cone pigment density difference refers to a change in light absorption by cones before and after bleaching of their visual pigments. With a television ophthalmoscope image processor, we measured the foveal cone pigment density difference in patients with retinitis pigmentosa (RP), good central vision, and no clinically apparent foveal lesion. Foveal reflectance was obtained at 12 different wavelengths of illumination. Compared with similar-aged normal subjects, most patients with dominantly inherited RP had normal or minimally reduced cone pigment density difference within the central fovea, relatively lower than normal density difference at the foveal margin, and increased foveal reflectance. Compared with these normal subjects, patients with recessively inherited RP had significantly reduced cone pigment density difference within the central fovea, relatively more normal density difference at the foveal margin, and normal foveal reflectance.
Kilbride PE, Fishman M, Fishman GA, Hutman LP. Foveal Cone Pigment Density Difference and Reflectance in Retinitis Pigmentosa. Arch Ophthalmol. 1986;104(2):220-224. doi:10.1001/archopht.1986.01050140074023