Abstract
An adaptive optics scanning laser ophthalmoscope (AO-SLO) is adapted to provide optical coherence tomography (OCT) imaging. The AO-SLO function is unchanged. The system uses the same light source, scanning optics, and adaptive optics in both imaging modes. The result is a dual-modal system that can acquire retinal images in both en face and cross-section planes at the single cell level. A new spectral shaping method is developed to reduce the large sidelobes in the coherence profile of the OCT imaging when a non-ideal source is used with a minimal introduction of noise. The technique uses a combination of two existing digital techniques. The thickness and position of the traditionally named inner segment/outer segment junction are measured from individual photoreceptors. In-vivo images of healthy and diseased human retinas are demonstrated.
Highlights
The invention of scanning laser ophthalmoscopy (SLO) [1,2] and optical coherence tomography (OCT) [3] represents two major advances in ophthalmoscopy
The lateral resolution is inversely proportional to the numerical aperture (NA) and the axial resolution is inversely proportional to the square of the NA
The function method provides a coherence profile that is of a near perfect Gaussian shape, but at the cost of a decreased SNR
Summary
The invention of scanning laser ophthalmoscopy (SLO) [1,2] and optical coherence tomography (OCT) [3] represents two major advances in ophthalmoscopy. Confocal gating [4] bestows SLO with the ability to discriminate in depth, (moderately) improved lateral resolution, and significantly enhanced imaging contrast. For an eye with perfect optical quality, when the confocal pinhole is optimized, the lateral and axial resolutions for a 6 mm pupil and 600 nm light are about 1.9 μm and 33 μm, respectively [5]. Rather than being limited by the NA of the eye, the depth resolution of OCT is dependent on the spectral bandwidth of the imaging light source being used [3]. By using broadband sources in-air axial resolutions of 1.5 μm have been reported [6,7]. The lateral resolution of OCT is dependent on the NA of the eye
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