We present evidence for the wavelength dependence of the directionality of light reflected from cone receptor cells (optical Stiles–Crawford effect): Blue light is more directional than red. According to the waveguide-scattering model of Marcos et al. [J. Opt. Soc. Am. A <b>15</b>, 2012 (1998)], directionality is the sum of a waveguide component and a scattering component. The latter is proportional to 1 over wavelength squared, and it is related to the row-to-row spacing of the cone lattice. Our results allow a firm confirmation of Marcos et al.’s theory. For a 1.9-deg foveal area, group mean (<i>n</i> = 18) cone spacing was 3.42 μm, in good agreement with anatomical data. Group mean waveguide directionality was 0.077 mm<sup>−2</sup>.
© 2003 Optical Society of America
(170.6510) Medical optics and biotechnology : Spectroscopy, tissue diagnostics
(290.5880) Scattering : Scattering, rough surfaces
(330.4300) Vision, color, and visual optics : Vision system - noninvasive assessment
(330.5310) Vision, color, and visual optics : Vision - photoreceptors
(330.5370) Vision, color, and visual optics : Physiological optics
Niels P. A. Zagers, Tos T. J. M. Berendschot, and Dirk van Norren, "Wavelength dependence of reflectometric cone photoreceptor directionality," J. Opt. Soc. Am. A 20, 18-23 (2003)