Abstract
Purpose :
Clinical optical coherence tomography (OCT) is an indispensable tool for managing glaucoma but may lack the resolution and sensitivity to detect progression at the level of retinal ganglion cells. Here, we investigate the use of adaptive optics optical coherence tomography (AO-OCT) to spatially and temporally resolve change in ganglion cell layer (GCL) somas located in glaucomatous arcuate damage and compare to clinical OCT measurements.
Methods :
The Indiana AO-OCT system was used to acquire volumetric images (1.5°x1.5°) at three adjacent retinal locations traversing into the arcuate defect (4-6° inferior-nasal to the fovea) of a glaucoma subject on a stable antihypertensive medication regimen. Spectralis OCT scans (30°x30°; B-scans spaced at 134 µm) were also acquired. All retinal locations were reimaged two years later with both instruments. For analysis, four subregions were selected from the AO-OCT images that sampled into the arcuate defect. Spatial coordinates of GCL soma centers were identified and marked manually in three dimensions. Soma counts were compared across the two-year interval to determine annual loss rate (%/yr). The distribution of soma coordinates projected axially was used as a cellular-level metric of GCL thickness and compared at the two time points to determine GCL thickness change. GCL thickness change was also measured with Spectralis OCT using local B-scans and local thickness maps averaged over a 1-mm diameter region centered at the AO-OCT retinal location.
Results :
A total of 1,221 GCL somas were identified in the baseline and 2-years-later AO-OCT images with soma counts decreasing in all four subregions: 195→183, 242→212, 145→134, and 57→53 somas. Count decreases correspond to annual loss rates of 3.1%, 6.2%, 3.8%, and 3.5%, which are 20-40X higher than expected due to aging (0.15%). The 2X variation in annual loss across the arcuate defect (3.1-6.2%) indicates that different regions of the defect may progress differently. The distribution of somas in depth across GCL was either uni- or bi-modal and decreased in width by 6.5% (2 µm) and 9.2% (3 µm) in the first two subregions and did not change in the two deeper subregions where fewer somas were found. Spectralis OCT revealed 2-3µm (B-scan) and 1µm decreases (thickness map) in GCL thickness.
Conclusions :
AO-OCT detects glaucoma progression at the level of somas and to a higher degree of discriminability than clinical OCT.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.