Differential detection of retinal directionality.

Salihah Qaysi,Brian Vohnsen,Denise Valente

doi:10.1364/boe.9.006318

Salihah Qaysi, Brian Vohnsen + Show 1 more

Open Access

https://doi.org/10.1364/boe.9.006318

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Abstract

An adaptive optics fundus camera has been developed that uses simultaneous capture of multiple images via adjacent pupil sectors to provide directional sensitivity. In the chosen realization, a shallow refractive pyramid prism is used to subdivide backscattered light from the retina into four solid angles. Parafoveal fundus images have been captured for the eyes of three healthy subjects and directional scattering has been determined using horizontal and vertical differentials. The results for the photoreceptor cones, blood vessels, and the optic disc are discussed. In the case of cones, the observations are compared with numerical simulations based on a simplistic light-scattering model. Ultimately, the method may have diagnostic potential for diseases that perturb the microscopic structure of the retina.

Highlights

Vision is sensitive to the angle of incidence of light on the retina as evidenced by the psychophysical Stiles-Crawford effect of the first kind (SCE-I) [1,2,3,4,5]
Only light in the outer photoreceptor segments matter, whereas for imaging scattering from refractive index inhomogeneities at any location within the eye may contribute to images
We have reported on a new directional sensitive fundus camera that uses a refractive pyramid in the conjugate pupil plane to allow simultaneous capture of four images corresponding to light scattered by the retina into adjacent solid angles in the horizontal and vertical directions

Summary

Introduction

Vision is sensitive to the angle of incidence of light on the retina as evidenced by the psychophysical Stiles-Crawford effect of the first kind (SCE-I) [1,2,3,4,5]. The causes of scattering within photoreceptors remain a topic of debate with likely contributions from inner/outer segment junctions and outer segment terminations [13,14,15,16]. One such contribution is the refractive index contrast between densely packed high-index mitochondria organelles and the surrounding cellular matrix in the ellipsoid [17] and gaps, or lack of membrane invaginations (defects), have been suggested to cause reflections [18]. The methods allow determination of an effective directionality parameter for light scattering that is similar, though not identical, to the directionality found by psychophysical means [2,4,10]

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