Risk factors associated with progressive nerve fiber layer thinning in open-angle glaucoma with mean intraocular pressure below 15 mmHg

The purpose of this study was to identify risk factors associated with progressive retinal nerve fiber layer(RNFL) thinning of open-angle glaucoma(OAG) in patients whose intraocular pressure(IOP) was maintained low with medical treatment. Based on a retrospective review of medical records, OAG patients with >= 60 months of follow-up and mean IOP below 15 mmHg were recruited. All eyes underwent IOP measurement with Goldmann applanation tonometer(GAT), standard automated perimetry(SAP), and cirrus optical coherence tomography(cirrus OCT) at 6 month or 1 year intervals. RNFL thinning was assessed using the Guided Progression Analysis(GPA) software. Forty-one eyes of 41 patients (mean age 54.9 +/- 13.5) were followed up for 77.8 +/- 7.8 months. GPA detected 20 eyes (48.8%) with progressive RNFL thinning(-1.5 +/- 0.5 um/year), who were subsequently classified as the 'rapid progression group.' Those whose rate of change in RNFL thickness was slower than -1.00 mu m/year was classified as the 'slow progression group' (n = 21, -0.0 +/- 0.4 um/year, P < 0.001). Mean IOP after initiating therapy was 13.2 +/- 1.1 mmHg in the rapid progression group and 13.1 +/- 1.3 mmHg in the slow progression group (P = 0.300; 14.8 +/- 10.0% vs. 19.6 +/- 12.4% reduction, P = 0.155). Disc hemorrhage was found to more frequently occur in the rapid progression group (P = 0.001). Multivariate logistic regression analysis showed that patients with disc hemorrhage were at a higher risk for progressive RNFL thinning in OAG (OR 37.529 95% CI 2.915-483.140) after adjusting for baseline co-variates (P = 0.005). In conclusion, disc hemorrhage is associated with progressive RNFL thinning in OAG with well-maintained IOP. Factors other than IOP appear to also play a role in OAG progression.