Abstract
Confocal scanning laser ophthalmoscopy (cSLO) enables high-resolution and high-contrast imaging of the retina by employing spatial filtering for scattered light rejection. However, to obtain optimized image quality, one must design the cSLO around scanner technology limitations and minimize the effects of ocular aberrations and imaging artifacts. We describe a cSLO design methodology resulting in a simple, relatively inexpensive, and compact lens-based cSLO design optimized to balance resolution and throughput for a 20-deg field of view (FOV) with minimal imaging artifacts. We tested the imaging capabilities of our cSLO design with an experimental setup from which we obtained fast and high signal-to-noise ratio (SNR) retinal images. At lower FOVs, we were able to visualize parafoveal cone photoreceptors and nerve fiber bundles even without the use of adaptive optics. Through an experiment comparing our optimized cSLO design to a commercial cSLO system, we show that our design demonstrates a significant improvement in both image quality and resolution.
Highlights
The confocal scanning laser ophthalmoscope is capable of producing high-contrast retinal images by raster scanning a laser spot and detecting backscattered light through a confocal pinhole.[1,2,3] High-contrast images are achieved because both the method of raster scanning and the use of a confocal pinhole allow for the minimization of optical cross talk, defined as unwanted light scattered from areas outside the focal volume.[4]cSLO systems have been widely adapted for various clinical applications
The relative location of a retinal image is given by the eccentricity which is defined as the distance in degrees between the fovea and the center of the image
We describe pinhole size in terms of the times-diffraction-limited spot size (TDL), which is the pinhole size normalized with respect to the Airy disc diameter of the collection optics (TDL 1⁄4 pinhole size∕Airy disc diameter)
Summary
The confocal scanning laser ophthalmoscope (cSLO) is capable of producing high-contrast retinal images by raster scanning a laser spot and detecting backscattered light through a confocal pinhole.[1,2,3] High-contrast images are achieved because both the method of raster scanning and the use of a confocal pinhole allow for the minimization of optical cross talk, defined as unwanted light scattered from areas outside the focal volume.[4]cSLO systems have been widely adapted for various clinical applications. Integration of adaptive optics with cSLO has enabled visualization of individual cone photoreceptors including those at the fovea where they are most closely packed,[11,12,13] and more recently rod photoreceptors,[14] which are smaller than foveal cone photoreceptors. Many of these exciting advances in cSLO application are achieved with relatively more expensive, complex, and larger-footprint designs (especially in the case of adaptive optics-based-systems).
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