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Kazuhiro Kurokawa, James A. Crowell, Furu Zhang, Ayoub Lassoued, Donald Thomas Miller; Measuring neuron loss in the retinal ganglion cell layer in healthy subjects. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1781.
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© ARVO (1962-2015); The Authors (2016-present)
Ganglion cells (GCs) are the primary cell type lost in diseases of the optic nerve such as glaucoma. There are established intervention strategies but assessing an individual patient’s glaucoma risk is limited by our inability to directly assess GC degeneration and loss. Furthermore, we need adequate measurement sensitivity to distinguish glaucomatous loss from normal aging-related loss. We test the efficacy of adaptive optics optical coherence tomography (AO-OCT) to track individual GCL somas, detect their loss over a period of one year in normal healthy subjects, and estimate the adequacy of our methods for studying glaucomatous GC loss.
Four eyes of four subjects (37±14 (average±SD) years old) were imaged with the Indiana AO-OCT system. AO-OCT volumes were acquired of 1.5°×1.5° (h×v) retinal patches at five different retinal locations temporal to fovea (1.5°-3°, 3°-4.5°, 6°-7.5°, 8°-9.5°, 12°-13.5°). An additional two nasal locations (1.5°-3°, 3°-4.5°) were imaged in one of the subjects. To visualize the GCL somas, 150 to 200 AO-OCT volumes were acquired of the same GCL soma patch, registered to each other using an improved 3D strip-wise registration algorithm, and averaged. From the registered and averaged AO-OCT volumes, we identified individual GCL somas and quantified their morphometry (e.g., soma density and diameter). We repeated the measurements one year later and identified lost GCL somas. Soma loss rate was defined as the ratio of the total number of somas lost to the total number of somas present. We analyzed repeated measures of GCL soma loss in a subset of the AO-OCT volumes using three graders.
The GCL soma loss rate across all retinal locations and subjects was 0.15%±0.05%/yr (average±SD), less than reported in cross-sectional histologic studies (~0.5%) and more than 30X smaller than the ~5% expected from glaucoma progression. Four pairs of volumes were examined for repeatability (baseline and one year later) and the graders were 100% consistent in identifying lost somas (0-2 losses per pair).
AO-OCT provides exquisite sensitivity to measure GCL soma loss and thus offers the potential for extremely early detection of disease onset.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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