Effect of wavelength on in vivo images of the human cone mosaic.

In images of the human fundus, the fraction of the total returning light that comes from the choroidal layers behind the retina increases with wavelength [Appl. Opt. 28, 1061 (1989); Vision Res. 36, 2229 (1996)]. There is also evidence that light originating behind the receptors is not coupled into the receptor waveguides en route to the pupil [S. A. Burns et al., Noninvasive Assessment of the Visual System, Vol. 11 of 1997 Trends in Optics and Photonics Series, D. Yager, ed. (Optical Society of America, 1997), p. al; Invest. Ophthalmol. Visual Sci. 38, 1657 (1997)]. These observations imply that the contrast of images of the cone mosaic should be greatly reduced with increasing wavelength. This hypothesis was tested by imaging the light distributions in both the planes of the photoreceptors and the pupil at three wavelengths, 550, 650, and 750 nm, with the Rochester adaptive optics ophthalmoscope. Surprisingly, the contrast of the retinal images varied only slightly with wavelength. Furthermore, the ratio of the receptorally guided component to the total reflected light measured in the pupil plane was found to be similar at each wavelength, suggesting that, throughout this wavelength range, the scattered light from the deeper layers in the retina is guided through the receptors on its return path to the pupil.