Optical coherence angiography of optic disc in eyes with primary open‐angle glaucoma and normal tension glaucoma with equal levels of structural damage

Abstract Purpose: To compare visual field (VF), nerve fibre and ganglion cell loss and changes in peripapillary vasculature in age matched patients with normal‐tension (NTG) and high tension glaucoma (HTG) at an equal level of glaucomatous structural damage of the optic nerve head (ONH). Methods: For the present study a retrospective analysis of patients with NTG and HTG was performed. One eye of each patient was randomly assigned for further analysis. To provide a reliable case by case match of HTG and NTG eyes, an equal optic disk size as measured by available spectral‐domain OCT system (RTVue XR OCT Avanti System; Optovue Inc., Fremont, CA) and an equal estimated excavation of the optic disk were chosen. Optic nerve head parameters, retinal nerve fibre layer (RNFL) ganglion cell (GCC) thickness and vessel densities (VD) in the peripapillary area were measured automatically by OCT with a respective software. Forty eyes with NTG, were matched according to the same glaucomatous ONH damage based on cup to disc ratio rim area and disc size with 40 eyes with HTG. Results: Mean age of patients was 68.5 ± 12 (27–84) years. The visual field index, RNFL, GCC thickness and peripapillary VDs in the HTG eyes were similar to those in the NTG eyes (mean VFI 79.6 vs. 78.8 p = 0.84, mean RNFL thickness 71.5 vs. 72.05 μm p = 0.87, mean GCC thickness 76.2 vs. 74.5 μm p = 0.62, mean peripapillary VD 43.6 vs. 43.8% p = 0.87). There was no difference in sectoral RNFL thickness and peripapillary VDs between HTG and NTG. In both groups, univariate regression analysis using the Pearson correlation coefficient showed VFI significantly correlated with RNFL thickness (NTG r = 0.423 p = 0.006 HTG r = 0.514 p = 0.002), and peripapillary VD (NTG r = 0.793 p < 0.001 HTG p = 0.534 p = 0.001) in both groups but with GCC thickness (NTG r = 0.585 p < 0.001) only in eyes with NTG. Conclusions: At an equal level of glaucomatous structural damage of the ONH indicated by cup to disk ratio and RNFL thickness, NTG patients seem to have same losses of peripapillary vasculature. Visual field index correlated with RNFL thickness and peripapillary vessel density in both groups.