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A Roorda, F Romero-Borja, WJ Donnelly III, TJ Hebert, H Queener; Dynamic Imaging of Microscopic Retinal Features with the Adaptive Optics Scanning Laser Ophthalmoscope . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4377.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Scanning laser ophthalmoscopes (SLO) provide high contrast images and axial sections of the ocular fundus, but with limited spatial resolution due to the aberrations of the eye. We present a custom-built SLO that uses adaptive optics (AO) to correct the higher order aberrations of the eye, and present the first dynamic images that use AO to push the limits of resolution in the living human eye to a microscopic level. Methods: The AOSLO captures 512 X 512 pixel images at 30 frames per second. The imaging field is adjustable from 4 X 4 to 1 X 1 degrees. Initial measurements were made with a 0.0175 NA collection lens focusing onto a confocal pinhole with a diameter of 80 micrometers. The AO system uses a Shack-Hartmann wavefront sensor coupled with a Xinetics 37-channel deformable mirror to correct the monochromatic aberrations in the eye over a 7 mm pupil. Aberrations are corrected on both the ingoing and outgoing light path. The AOSLO uses a common light source and optical path for both retinal imaging and wavefront sensing, thereby reducing non-common path wavefront errors and simplifying the instrument design. Axial sectioning is done by applying a focus adjustment directly onto the deformable mirror. The imaging system uses all-digital image acquisition and storage on a PC desktop computer. Results: Real-time images with the AOSLO reveal the dynamic microscopic structure of the retina. The flow of single white blood cells through the smallest capillaries near the fovea is directly visible in the unprocessed digital video images. Individual photoreceptors are also visible. Axial sections reveal the fine structure of the capillary network around the foveal avascular zone. Adaptive optics increase lateral and axial resolution, and also increase the amount of light that is collected through the confocal pinhole. Conclusion: Adaptive optics can be used effectively in a scanning laser ophthalmoscope to facilitate dynamic imaging of microscopic structure in the living human retina.
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