Poster Session II: Understanding scattering in high-resolution retinal imaging.

Abstract

In conventional fundus images the contrast relates to scattering and absorption of light. Here, we report on modeling of high-resolution retinal imaging to understand the role of mitochondria light scattering in the ellipsoid of photoreceptors. We evaluate the directionality appearance of the photoreceptors, and its relation to drusen appearance in age-related macular degeneration (AMD). The refractive index contrast of the mitochondria collectively resembles that of micron-sized reflectors. Obliqueness of the scattering results in vignetting by the pupil that impacts on the brightness of the photoreceptors. Our hypothesis is that in early-stage AMD, drusen will perturb the photoreceptor alignment and thus cause oblique scattering and reduced brightness on the slope of the drusen in high-resolution retinal images. We model how this affects the observable photoreceptor mosaic both in the healthy eye and in eyes with AMD. The results confirm that the annular dark ring around drusen is likely caused by oblique scattering. We use a model eye to test the hypothesis with a reflective mask emulating the photoreceptor mosaic An SLM is used for amplitude modulation in the pupil and differential imaging allows for capturing off-axis images with an appearance like that of phase contrast images. Further refinement of the model eye may be a valuable way to test new imaging modalities prior to their implementation in the real eye.