Diagnostic Potential of Ganglion Cell Layer to Inner Plexiform Layer Thickness Ratio in Distinguishing Branch Retinal Vein Occlusion from Primary Open-Angle Glaucoma.

Purpose: To investigate the diagnostic utility of the ganglion cell layer (GCL) to inner plexiform layer (IPL) thickness ratio, in differentiating branch retinal vein occlusion (BRVO) from primary open-angle glaucoma (POAG) exhibiting hemifield defects. Given the impact of POAG on the ganglion cell complex (GCC), we hypothesized that POAG wound show disproportionately greater thinning in the GCL and tested if the GCL:IPL ratio could differentiate between these two conditions. Methods: We conducted a retrospective case series of macular OCT images (Spectralis [Heidelberg Engineering, Heidelberg, Germany]) from patients with old BRVO/HRVO and POAG. Inclusion criteria were 1) BRVO/HRVO Diagnosis at least 6 months, without macular edema at the time of imaging, and 2) POAG with an arcuate or altitudinal hemifield defect on Humphrey Visual Field (Carl Zeiss Meditec, Inc., Dublin, CA). Exclusion criteria were the presence of poor-quality OCT scans, history of pan-retinal photocoagulation (PRP), corneal, retinal or neuroophthalmological conditions. Using the Heidelberg automated segmentation analysis of the macular cube, a 20-degree PMB grid was centered over the foveal pit and utilized to generate a 6×10 grid to provide a comprehensive assessment of the retinal layers in the macular region. The GCL:IPL ratio was calculated by dividing the GCL by the corresponding IPL thickness. Calculation of the inner retina:total retina ratio was done in an identical manner, and the average thicknesses and ratios were then compared using the Wilcoxon rank-sum test (MedCalc Statistical Software, Ostend Belgium). Results: Final analysis included 60 eyes of 60 patients (mean age 67 ± 13 years; 57% female; 42% African American, 28% Hispanic, 12% White, 18% as others) diagnosed with old BRVO/HRVO (n = 30) or POAG (n = 30). Patients with POAG had an average visual field mean deviation of -16.22dB ± 5.02. The GCL:IPL ratio was significantly lower in patients with POAG was 0.91 (95% CI [0.85, 0.94]) compared to RVO with 1.14 (95% CI [1.09, 1.17], ( Conclusions: There was disproportionately greater thinning in the GCL compared to the IPL in patients with POAG compared to those with RVO as evidenced by the observed differences in GCL:IPL ratios. Our findings characterized by high AUC and sensitivity suggest that the GCL:IPL ratio has potential to be a marker for distinguishing between old BRVO and POAG with hemifield defects.