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Zhuolin Liu, Kazuhiro Kurokawa, Furu Zhang, Donald T Miller; In vivo imaging of human retinal ganglion cells with AO-OCT. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3430.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is a neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and is a leading cause of blindness worldwide. While effective therapeutics exist, early detection of RGC loss has remained elusive regardless of method. Here we propose a new method based on adaptive optics optical coherence tomography (AO-OCT) that permits visualization of individual RGC soma in vivo and thus the potential for direct detection of cell loss.
Four healthy subjects (age: 24-50 yrs) were imaged at five macular locations (1.5°-3°, 3°-4.5°, 6°-7.5°, 8°-9.5°, and 12°-13.5°) temporal to the fovea using the Indiana AO-OCT system. Corresponding nasal locations were also imaged for one of the subjects. For each retinal location, 1.5°x1.5° field-of-view AO-OCT videos were acquired with system focus at the RGC layer. Volumes were registered in three dimensions with subcellular accuracy and averaged to increase image contrast of RGC somas. In post processing, spatial coordinates of RGC soma centers were identified and marked manually using custom software. Soma coordinates were used to determine soma stack depth, density, and diameter. Voronoi analysis was used for RGC density measurement with exclusion of blood vessels.
A 3D mosaic of RGC somas was observed in every subject and retinal eccentricity imaged, a total of 25 locations. The stack depth reached a maximum of 4 to 5 somas near 3°, decreased rapidly towards the fovea and more slowly to a minimum stack depth of one further away. A stack depth of two or more somas was observed up to 8°-9.5° and a single depth at 12°-13.5°. In the two subjects processed to date, average soma densities (cells/mm2) were 16,741 (1.5°-3°), 19,824 (3°-4.5°), 12,921 (6°-7.5°), 8,928 (8°-9.5°), and 3,743 (12°-13.5°). The distribution (average ± stdev) of soma diameter increased from 13.0±2.8μm at 1.5°-3° to 14.5±3.3 μm at 12°-13.5°. The vast majority of the somas were of small size (12-15 μm), but notably larger somas (20-22 μm) were also observed and became more numerous with retinal eccentricity. Our measurements of soma stack depth, density, and diameter are consistent with histologic reports .
AO-OCT imaging permits visualization and quantification of human RGC somas across the macula. To the best of our knowledge, this is the first report of the 3D distribution and size of RGC soma in the living human eye. Curcio CA, et al. J.Comp.Neurol. 1990.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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