Abstract
While fluorescent contrast is widely used in ophthalmology, three-dimensional (3D) fluorescence retinal imaging over a large field of view (FOV) has been challenging. In this paper, we describe a novel oblique scanning laser ophthalmoscopy (oSLO) technique that provides 3D volumetric fluorescence retinal imaging with only one raster scan. The technique utilizes scanned oblique illumination and angled detection to obtain fluorescent cross-sectional images, analogous to optical coherence tomography (OCT) line scans (or B-scans). By breaking the coaxial optical alignment used in conventional retinal imaging modalities, depth resolution is drastically improved. To demonstrate the capability of oSLO, we have performed in vivo volumetric fluorescein angiography (FA) of the rat retina with ~25μm depth resolution and over a 30° FOV. Using depth segmentation, oSLO can obtain high contrast images of the microvasculature down to single capillaries in 3D. The multi-modal nature of oSLO also allows for seamless combination with simultaneous OCT angiography.
Highlights
Fluorescence retinal imaging is an essential tool in vision science, and has important clinical applications in ophthalmology
We first compressed the axial scale of the optical coherence tomography (OCT) image assuming a 1.33 refractive index in the gel and warped the oblique scanning laser ophthalmoscopy (oSLO) image to match OCT using the method in our previous publication [28]
As the refractive index is a constant within the gel, OCT provides an absolute scale for characterization of the axial resolution of oSLO
Summary
Fluorescence retinal imaging is an essential tool in vision science, and has important clinical applications in ophthalmology. Four major forms of fluorescent contrasts are utilized. Fluorescein angiography (FA) has been a gold-standard imaging technique for evaluation of the retinal vasculature for more than 50 years [1]. Indocyanine green angiography (ICGA) is utilized in cases where retinal hemorrhage may block FA signal or when the choroidal vasculature is the suspected area of pathology. Blue light and NIR fundus autofluorescence (FAF), techniques not requiring exogenous contrast agents, take advantage of the intrinsic autofluorescence (AF) of retinoids in photoreceptors [2] and lipofuscin and melanin in the RPE [3, 4] to image areas of pathology in non-exudative age-related macular degeneration [5] and detect photoreceptor damage indicative of retinal dystrophies and degenerations [6]
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