Correlation of the Retinal Parapapillary Perfusion and the Retinal Vessel Oxygen Saturation in Glaucoma Patients

Reduced perfusion of the retinal parapapillary tissue is well documented in glaucoma patients. Whether or not this is a cause or result of the disease is however unknown. Studying the correlation of this perfusion and the retinal vascular oxygen saturation (O2S) could give clues to the retinal O2 consumption/demand and provide an answer to this question.

Seventeen eyes of 17 healthy controls and 32 eyes of 32 patients with primary open angle glaucoma were prospectively recruited. Global and sectoral nerve fiber layer (NFL) thickness was measured with optical coherence tomography (OCT); parapapillary OCT-angiography was performed and quantified into vascular density (VD) and perfusion density (PD). Retinal vascular O2S was measured.

Global and sectoral NFL thickness, VD, PD (except for temporal sector of VD), and arteriovenous difference of O2S (AV-D) were lower in glaucomatous eyes compared with controls (P < 0.05 for all). A significant inverse correlation of venous O2S with global VD (r = -0.37, P = 0.04) and PD (r = -0.37, P = 0.04) and a direct correlation of the AV-D with global VD (r = 0.50, P = 0.004) and PD (r = 0.49, P = 0.004) were observed. In sector analysis, the strongest correlation of AV-D with VD and PD was seen in inferior (VD: r = 0.52, P = 0.001; PD: r = 0.55, P = 0.002) and superior (VD: r = 0.454, P = 0.009; PD: r = 0.46, P = 0.008) segments.

In glaucomatous eyes, there exists a direct correlation of the AV-D to the VD and PD with the strongest correlation being in superior and inferior segments where typically tissue loss occurs. This could possibly be explained by the loss of tissue being followed by the reduced density.