Comparing rates of retinal nerve fibre layer loss with GDxECC using different methods of visual-field progression

BACKGROUND: This prospective analysis was designed to examine the rate of RNFL loss using scanning laser polarimetry (GDx enhanced corneal compensation (GDxECC)) in progressing versus non-progressing eyes using various methods to define functional progression. METHODS: Glaucoma suspect and glaucomatous eyes with ≥3 years of follow-up participating in the Advanced Imaging for Glaucoma Study were enrolled. All eyes underwent standard automated perimetry (SAP) and GDxECC imaging every 6 months. The annual rate of RNFL loss with GDxECC was calculated using linear regression analysis. Functional progression was determined using the Early Manifest Glaucoma Trial (EMGT) criterion, SAP Visual Field Index (VFI) and Progressor software. RESULTS: Fifty-three eyes (30 glaucoma suspect, 23 glaucoma) of 53 patients (mean age 64.5±10.7 years, range 42-79) were enrolled. Eighteen eyes (40%) demonstrated SAP progression during the follow-up period using the Progressor criterion, 10 eyes (18.9%) using the VFI criterion, and 3 eyes (5.7%) using the EMGT criterion. The annual rate (μm/year) of mean RNFL loss was significantly greater (p<0.05) in progressing versus non-progressing eyes using Progressor (-1.24±0.99 vs -0.18±0.49), EMGT (-1.95±0.99 vs -0.46±0.78) and VFI (-1.11±0.64 vs -0.41±0.85) criteria. CONCLUSION: Despite differences in the criteria used to judge functional progression, progressing eyes have a significantly greater rate of RNFL loss measured using GDxECC as compared with non-progressing eyes.