Optic nerve head diurnal vessel density variations in glaucoma and ocular hypertension measured by optical coherence tomography angiography.

ABSTRACT

BACKGROUND/AIMS: To evaluate diurnal variations in optic nerve head (ONH) vessel density assessed by optical coherence tomography angiography (OCT-A) in healthy subjects, ocular hypertension (OHT), and open-angle glaucoma (OAG) patients. METHODS: Forty subjects (OAG, 21; OHT, 6; healthy, 13) were assessed for vessel density percentage (VD%) and flow index in the ONH (NH VD%, NH index), and in the radial peripapillary capillary layer (RPC VD%, RPC index) at 900, 1100, 1400, 1600, and 1800 on a single day. Repeated measures ANOVAs were used to test for changes in the parameters measured at multiple time points. RESULTS: All OCT-A parameters analyzed at the different time points were statistically lower in the OAG patients compared to both the OHT and healthy groups (p < 0.05). In the OAG group, the NH index, RPC index, NH VD%, and RPC VD% were statistically lower at 1800 compared to 1400, and the RPC VD% was statistically lower at 900 than 1400. In the OHT group, the RPC index was statistically lower at 900 than 1100. In the healthy group, the NH VD% and RPC VD% were statistically lower at 1600 than 1800, and the RPC index was statistically lower at 900 than 1100. No other statistically significant difference was found in none of the three groups comparing any other time point (p > 0.05). CONCLUSION: In healthy subjects, OHT and OAG patients, the variations in the OCT-A derived parameters were relatively small. These results suggest that in the clinical practice the OCT-A assessment can be performed independently of the time of the day, contrasting IOP evaluation.