Decreasing Retinal Capillary Perfusion and Increasing Retrobulbar Blood Flow Are Correlated With Structural Changes in Patients With Glaucoma

Abstract

Purpose: : To examine changes in retinal capillary blood flow and retrobulbar blood flow in relation to changes in retinal nerve fiber layer (RNFL) thickness after one year in patients with primary open-angle glaucoma (OAG).

Methods: : Retrobulbar blood flow and retinal capillary perfusion were examined in relation to RNFL thickness after one year in 76 patients (age 67.7, 43 females) with OAG participating in the Indianapolis Glaucoma Progression Study (IGPS). Color Doppler imaging (CDI) of retrobulbar blood vessels and retinal capillary perfusion was examined with confocal scanning laser Doppler flowmetry (HRF). RNFL thickness was assessed with both optical coherence tomography (OCT) and Heidelberg Retinal Tomograph.The change from baseline to one year was calculated for each parameter and Pearson correlation analysis examined the relationship between changes in retinal capillary blood flow in relation to changes in RNFL thickness. P <0.05 were considered statistically significant.

Results: : Changes in ophthalmic artery peak and end-diastolic blood flow velocities were significantly negatively correlated with changes in average RNFL thickness and superior, nasal and inferior regions (r=-0.37 to -0.24, p=0.001 to 0.036). Central retinal artery peak systolic velocity was negatively correlated with average and superior region RNFL thickness (r=-0.27, p=0.02; r=-0.24, p=0.036), respectively. Temporal short posterior ciliary artery end diastolic velocities were negatively correlated with superior RNFL thickness (r=-0.23, p=0.04) while changes in nasal peak systolic velocity was negatively correlated with changing nasal RNFL (r=-0.30, p=0.01).A decrease in mean retinal capillary blood flow in both the superior and inferior retina significantly correlated with increasing ophthalmic artery peak systolic velocity (r=-0.24, p=0.047; r=-0.26, p=0.025).Mean retinal capillary perfusion in the superior retina was associated with thinning of the mean RFNL (r=0.24, p=0.047) measured by HRT and RNFL thickness (superior, r=0.29, p=0.014; inferior r=0.37, p=0.001; and average r=0.44, p=0.000) as measured by OCT.

Conclusions: : Decreasing retinal capillary blood flow is associated with thinning of the RNFL. The increase in retrobulbar blood flow may represent an attempt to augment diminished retinal capillary blood flow in order to maintain perfusion to retinal ganglion cells and prevent structural damage in patients with OAG.

Keywords: retina • blood supply • clinical (human) or epidemiologic studies: risk factor assessment