Purpose: To use optical coherence tomography (OCT) to investigate the qualitative and quantitative differences in the defects of the retinal nerve fiber layer (RNFL) in subjects with high tension primary open angle glaucoma and subjects with normal tension glaucoma.
Methods: RNFL was assessed with OCT in 21 eyes with high-tension glaucoma (HTG) and 20 eyes with normal-tension glaucoma (NTG). Regression analyses were performed to investigate the interaction of disease group and location for localized RNFL loss, and to predict diffuse and localized RNFL loss as a function of age, mean defect, spherical equivalent, disease group, and location. Local RNFL thicknesses for superior clock-hour regions were estimated after adjustment for the thicknesses of symmetrically opposed locations.
Results: There were no differences in mean age, visual field defect mean deviation, and refractive error between subjects in HTG and NTG groups. Diffuse RNFL thickness was not significantly different between the two groups [mean RNFL for NTG > HTG by 3.48 mum, 95% confidence interval (CI) -3.9 to 10.9 microm, p = 0.092]. There was no significant interaction of group and location for localized RNFL loss (p = 0.916). Local RNFL thickness at superior regions was not significantly different in the two groups, after adjustment for RNFL thickness at corresponding inferior locations (mean RNFL for NTG > HTG by 6.30 microm, 95% CI -1.08 to 13.7 microm, p = 0.34). RNFL thickness decreased, on average (1.88 microm/dB mean deviation, 95% CI 1.21 to 2.55 microm, p < 0.0001) and locally (1.37 microm/dB mean deviation, 95% CI 0.79 to 1.96 microm, p < 0.0001), with increasing severity of glaucoma.
Conclusion: There is no difference in the spatial pattern of RNFL defects, as assessed by the OCT, between HTG and NTG.