Correlation Among Choroidal, Parapapillary, and Retrobulbar Vascular Parameters in Glaucoma

Abstract

To study and compare the correlation among choroidal, parapapillary, and retrobulbar vascular parameters in healthy subjects, glaucoma suspects, and open-angle glaucoma (OAG) patients. Prospective observational clinical study. The study included one randomly selected eye from 21 normal subjects, 30 glaucoma suspects based on optic disc appearance, and 22 OAG patients. The pulsatile ocular blood flow (POBF), a measure of choroidal blood flow, was assessed using ocular blood flow analyzer whereas parapapillary blood flow and blood velocity of retrobulbar blood vessels were measured using scanning laser Doppler flowmetry and color Doppler imaging, respectively. All vascular parameters along with blood pressure and intraocular pressure measurements were obtained within a 2-hour period. Univariate regression analyses were used to evaluate the correlation of POBF values with parapapillary blood flow values, retrobulbar blood flow velocities, and resistive index, which represents vascular resistance, in each group. Two multiple linear regression models were created based on results of univariate analyses and included POBF, mean parapapillary blood flow, age, and mean ocular perfusion pressure; and POBF, temporal short posterior ciliary artery resistive index, age, and mean ocular perfusion pressure. POBF was significantly associated with parapapillary blood flow (r2 = 0.54; P < .001, positive correlation) and temporal short posterior ciliary artery resistive index (r2 = 0.39; P < .001, negative correlation) in normal subjects. Results were consistent when corrected for age, intraocular pressure, and blood pressure parameters. POBF values did not correlate with parapapillary blood flow values or temporal short posterior ciliary artery resistive index in glaucoma suspects or OAG patients. The relationships of POBF with parapapillary blood flow and calculated retrobulbar vascular resistance differs among normal subjects, glaucoma suspects, and OAG patients. This provides further evidence of vascular dysregulation in OAG.