Fundus reflectometry is a common in-vivo, noninvasive method to estimate the macular pigment optical density (MPOD). The measured density, however, can be affected by the individual’s intraocular scattering. Scattering causes a reduction in the contrast of the fundus image, which in turn leads to an underestimation of the measured density. Intraocular scattering was measured optically in a group of seven young, healthy subjects using the method of optical integration and was subsequently used to correctly estimate the MPOD from fundus images. It was shown that when scattering is not considered, the measured optical density using fundus reflectometry can be underestimated by as high as 16% for our group of subjects.
Light scattering in the human eye can deteriorate image quality and limit visual performance especially at the presence of
a glare source. Optical measurement of straylight in the human eye is a challenging task where issues related to various
inherent artifacts must be addressed. We report on a novel instrument based on the principle of double-pass optical
integration that has been adapted for fast measurements suitable for a clinical setting. The instrument utilizes a light
source formed by an array of green light emitting diodes that is projected onto the ocular fundus. The source has two
concentric parts, a disk (field angle 0-3 degrees) and an annulus (3 - 8 degrees) that are modulated at different
frequencies. A silicon photomultiplier receives the light reflected from the central part of the fundus and the Fourier
transform of the signal reveals the contribution of each part of the source. Their relative amplitude is used to quantify
light scattering by means of the straylight parameter. The instrument was initially validated using known diffusers.
Straylight in a cohort of cataract patients (N=39) was measured. The optically measured straylight parameter was
correlated to the clinical cataract grade as well to the psychophysically estimated value. The measurement method,
utilizing rotational symmetry and coding filed angles with different frequencies eliminates the need for a highperformance
camera and allows fast measurements. This approach can be further advanced with multiple wavelengths
and field angles to perform other measurements such as that of the macular pigment density.