The Relationship Between Ocular Perfusion Pressure and Ocular Blood Flow in Glaucoma Patients: The Indianapolis Glaucoma Progression Study

Abstract

Purpose: : To examine the relationship between ocular perfusion pressure and retrobulbar blood flow in open angle glaucoma (OAG) patients.

Methods: : 194 study visits (101 patients, mean age 65.6 SD 10.2 years, 57.4% female) of OAG patients participating in the Indianapolis Glaucoma Progression Study (IGPS) were analyzed. IOP was measured by Goldmann tonometry. Blood pressure was measured with an automated pressure sensing cuff. Ocular (OPP), systolic (SPP), and diastolic (DPP) perfusion pressures were calculated. Systolic (PSV) and diastolic (EDV) blood flow velocities and Pourcelot’s resistivity index (RI) were measured with color Doppler imaging (CDI) in the ophthalmic (OA), central retinal (CRA), and nasal and temporal short posterior ciliary arteries (N/TPCA). Correlation between CDI and perfusion pressure was determined by linear regression. Pearson correlation coefficients were utilized to assess the strength of the associations, and P values <0.05 were considered significant.

Results: : In the OA, the OPP and DPP positively correlated with the PSV (r=0.24 p=0.0004; r=0.17 p=0.009) and EDV (r=0.20 p=0.003; r=0.21 p=0.001). In the CRA, the OPP positively correlated with the PSV (r=0.14 p=0.03) and EDV (r=0.15 p=0.02 OPP), and the DPP positively correlated with the EDV (r=0.16 p=0.01). In both PCAs, the OPP was found to positively correlate with the PSV (r=0.14 p=0.02 NPCA; r=0.16 p=0.01 TPCA). In both PCAs, the OPP also positively correlated with the RI (r=0.15 p=0.02 NPCA; r=0.12 p=0.05 TPCA).

Conclusions: : In OAG patients, an increase in perfusion pressure is paralleled by an increase in PSV and EDV of the OA and CRA. Based on in vitro models, PSV and EDV increases are suggestive of volumetric blood flow increases. In the PCAs, an increase in perfusion pressure correlates with an increase in PSV and RI. Our data suggests that in OAG patients, the PCAs do not autoregulate in response to perfusion pressure as the retinal vasculature does. The optic nerve may therefore be vulnerable to IOP and blood pressure fluctuations.

Keywords: blood supply • intraocular pressure • imaging/image analysis: clinical