Enhanced retinal vasculature imaging with a rapidly configurable aperture.

Kaitlyn A Sapoznik,Stephen A Burns,Ting Luo,Raymond L Warner,Lucie Sawides,Alberto De Castro

doi:10.1364/boe.9.001323

Abstract

In adaptive optics scanning laser ophthalmoscope (AOSLO) systems, capturing multiply scattered light can increase the contrast of the retinal microvasculature structure, cone inner segments, and retinal ganglion cells. Current systems generally use either a split detector or offset aperture approach to collect this light. We tested the ability of a spatial light modulator (SLM) as a rapidly configurable aperture to use more complex shapes to enhance the contrast of retinal structure. Particularly, we varied the orientation of a split detector aperture and explored the use of a more complex shape, the half annulus, to enhance the contrast of the retinal vasculature. We used the new approach to investigate the influence of scattering distance and orientation on vascular imaging.

Highlights

When illuminated, retinal structures may directly scatter light back through the system pupil, and be captured directly by the imaging system, or may scatter light in other directions [1]
In current adaptive optics scanning laser ophthalmoscope (AOSLO) systems, two main approaches are utilized to capture multiply scattered light: 1) an offset aperture displaced from the center of the point spread function (PSF) [4] and 2) a split detector in which the center of the PSF is removed and light in two directions is collected [5]
When placed at a retinal conjugate plane, an spatial light modulator (SLM) can effectively be used as a configurable aperture

Summary

Introduction

Retinal structures may directly scatter light back through the system pupil, and be captured directly by the imaging system, or may scatter light in other directions [1]. Chui et al [4] first utilized multiply scattered light imaging within an AOSLO by using an offset aperture to improve imaging of vascular wall structures that were not readily observed in confocal imaging. Pathological changes to the vessel wall structure are of particular interest in subjects with diabetes and hypertension and have been observed with this technique [7, 8] This approach has proven useful in characterizing the murals cells of the retinal vasculature [9]; to detect subclinical vascular and cystic changes in subjects with diabetes [7]; characterize wall-to-lumen ratios (WLR) in normo-, hypo-, and hypertensive subjects [8]; provide perfusion maps comparable to AOSLO fluorescein angiography [10]; and detect erythrocytes in small capillaries to compute blood flow velocity [11]. The use of multiply scattered light photoreceptor imaging is expanding rapidly and is currently being investigated as a potential biomarker for therapeutic interventions in some hereditary retinal degenerations [18]

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Discussion

Conclusion