Purpose To determine factors influencing color Doppler imaging (CDI) measurements, to compare retrobulbar flow velocities between patients with glaucoma and healthy controls, and to describe the correlation between CDI and ocular pulse amplitude (OPA). Methods Patients with normal tension (n=28) or primary open angle glaucoma (n=19) and healthy controls (n=22) underwent CDI and OPA measurements. Intraocular pressure, corneal thickness, blood pressure, and heart rate were also measured. Spearman correlations were used to explore relations among these variables. A regression model for repeated measures was applied to compare between diagnostic groups the flow velocity indices in the retrobulbar vessels. Results Retrobulbar diastolic blood flow velocities correlated with diastolic blood pressure and perfusion pressure (range of Spearman rho [ρ] coefficients=0.25–0.28; P=0.044–0.013 for the different vessels). Corneal thickness showed a positive correlation with systolic and diastolic flow velocities in the central retinal artery (ρ=0.29 and 0.31; P=0.017 and 0.011 for peak systolic and end diastolic velocity, respectively). Systolic and diastolic blood flow velocities were reduced in the retrobulbar vessels of patients with normal tension glaucoma (P=0.0004) as well as primary open angle glaucoma (P=0.003) compared to healthy controls. A correlation was found between OPA and the resistive index in the retrobulbar vessels of the healthy controls (range ρ=0.42–0.53; P=0.059–0.014). Conclusions Retrobulbar blood flow velocities are reduced in patients with primary open angle glaucoma and normal tension glaucoma. Blood pressure and corneal thickness may influence CDI measurements. OPA correlates with the resistive index in CDI.
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