Abstract

The inside of the eye has the potential to act as an integrating sphere, since once in the eye there is little opportunity for light to exit the eye. This tendency is canceled over much of the spectrum by the presence of pigments, especially melanin, which absorb light and decrease the effective path length of light inside the eye. However, since long wavelengths of light penetrate more deeply into the retina and choroid (Norren and Tiemeyer; 1986, Delori and Pflibsen 1989, Eisner et al.;1996), being absorbed to a lesser extent by melanin, blood and other ocular pigments, there is a potential for the contrast of images to be decreased by scattering of light in the RPE and choroid. In patients this is more likely, since in many retinal diseases there are marked changes in the melanin content and distribution and, as a result, potentially increased scattering. One factor that is believed to decrease the sensitivity of the eye to stray light is the alignment of the cones such that their long axis points toward the center of the pupil (Laties and Enoch; 1971). Since the cones act as waveguides, aiming the cones towards the pupil should increase their sensitivity to light entering the eye from the pupil, and decrease sensitivity to light illuminating them from the sides. In addition, the cones are tapered, with the inner segments (where the presumed optical aperture resides) being larger than the outer segments. This tapering may also decrease the sensitivity of the cones to light illuminating them from behind. In the current paper we test this idea by “generating” a light which illuminates the retina from behind and measuring whether this light is guided by the cones back towards the pupil.

© 1997 Optical Society of America