A Method to Estimate the Amount of Neuroretinal Rim Tissue in Glaucoma: Comparison with Current Methods for Measuring Rim Area – Accepted Manuscript

Abstract: Purpose: To test whether the minimum rim area assessed by spectral domain optical coherence tomography (SD-OCT), based on the shortest distance from Bruch’s Membrane Opening (BMO) to the inner limiting membrane, corresponds more closely to retinal nerve fiber layer (RNFL) thickness and visual field mean deviation (MD) than current rim measures in early glaucoma.Design: Prospective cross-sectional study.Methods: 221 participants with non-endstage glaucoma or high-risk ocular hypertension performed standard automated perimetry, and received SD-OCT and confocal scanning laser ophthalmoscopy (CSLO) scans, on the same day. Rim area measured by CSLO was compared with three SD-OCT rim measures from radial B-scans: horizontal rim area between BMO and ILM within the BMO plane; mean minimum rim width (BMO-MRW); and minimum rim area (BMO-MRA) optimized within sectors and then summed. Correlations between these measures and either MD from perimetry or RNFL thickness from SD-OCT were compared using Steiger’s test.Results: RNFL thickness was better correlated with BMO-MRA (r=0.676) or BMO-MRW (r=0.680) than with either CSLO Rim Area (r=0.330, p<0.001) or Horizontal Rim Area (r=0.482, p<0.001).MD was better correlated with BMO-MRA (r=0.534) or BMO-MRW (r=0.546) than with either CSLO Rim Area (r=0.321, p<0.001) or Horizontal Rim Area (0.403, p<0.001). The correlation between MD and RNFL thickness was r=0.646.Conclusions: Minimum rim measurements from SD-OCT are significantly better correlated to both RNFL thickness and MD than rim measurements within the BMO plane, or based on the clinical disc margin. They provide new structural parameters for both diagnostic and research purposes in glaucoma.