Assessing the wavelength dependence of intraocular scattering by a new optical approach

Abstract

AbstractPurpose The wavelength dependence of the light scattering is related with the characteristics of the inhomogeneities in the ocular media, and therefore, an objective assessment could be used to the early detection of underlying ocular pathologies. We developed a new optical instrument for measuring light scattered in the human eye at different wavelengths.Methods Using a double‐pass configuration, series of disks of uniform radiance with an increasing angular dimension are sequentially projected on to the retina. As a light source, a white light halogen lamp is spectrally filtered by using a liquid crystal tunable filter, selecting three different wavelengths: 550, 600 and 650 nm (FWHM = ± 50 nm). The disk’s retinal images are recorded by a cooled electron‐multiplied CCD camera. The derivative of intensity at the center of each disk’s retinal image with respect to its radius provides the eye’s wide‐angle double‐pass point‐spread function (PSF). The method was applied in an artificial eye with different levels of induced scattering, and in a group of normal subjects.Results In the artificial eye, the increasing scattering induced is successfully discriminated at the more eccentric angular domain of the wide‐angle PSFs. In the group of subjects, the estimated wide‐angle PSFs differ from the lower to the larger wavelengths. The PSF at 550 nm is characterized by more intense light scatter in the angular range between 5 and 10 degrees, while the PSF at the 650nm showed a relatively increased scattered light between 0 and 2 degrees. This would be related to the deeper interaction of thConclusion An optical objective method is sensitive enough to detect consistently differences in light scatter for different wavelengths.