RGC Morphology of Eyes With POAG
By Lynda Seminara
Selected By: Prem S. Subramanian, MD, PhD
Investigative Ophthalmology & Visual Science
Liu et al. set out to describe the morphologic changes in retinal ganglion cells (RGCs) that occur in patients with primary open-angle glaucoma (POAG) associated with hemifield defect. Using adaptive optics (AO) OCT, they found that these patients had lower ganglion cell layer (GCL) soma density and symmetry, greater soma size, and more variation of GCL soma reflectance compared with healthy controls.
The study included six patients with early or moderate POAG and hemifield defect (mean age, 58 years) and six age-matched healthy controls (mean age, 61 years). All participants received in vivo high-resolution AO-OCT imaging of RGCs at the same primary locations of the macula. GCL somas were counted manually, and the morphologic parameters of GCL soma density, size, and symmetry were calculated. From these data, the relationship between RGC characteristics and functional visual field measurements was explored.
At 3, 6, and 12 degrees, GCL soma density was 12,799 ± 7,747 cells/mm2, 9,370 ± 5,572 cells/mm2, and 2,134 ± 1,494 cells/mm2 (respectively) in the glaucoma group, compared with 25,058 ± 4,649 cells/mm2, 15,551 ± 2,301 cells/mm2, and 3,891 ± 1,105 cells/mm2 (respectively) in the control group (p < .05 for all locations). These data represent reductions of 49%, 40%, and 45% for patients with glaucoma relative to controls. Soma diameter was significantly larger in glaucomatous eyes (mean, 14.20 ± 2.30 μm vs. 12.32 ± 1.94 μm in controls; p < .05 for all locations). Symmetry values were 0.36 ± 0.32 and 0.86 ± 0.13 for the glaucoma and control cohorts, respectively. AO-OCT also was useful for detecting subcellular reflectance changes in GCL somas and for tracking inner retinal changes in some eyes with POAG.
These results indicate that RGCs are equally affected by glaucoma throughout the macula but that loss of these cells affects vision more in the periphery, said the authors. This is likely due to reduced RGC density and decreased cone-to-RGC ratio in that region. The morphologic changes noted in this study are characteristic of hemifield defects, and the cellular-level structural loss in glaucomatous eyes correlated with loss of visual function. Therefore, the authors believe that AO-based morphologic parameters have the potential to be biomarkers for glaucoma.
The original article can be found here.