Visual Function Correlates with Blood Flow in Primary Open Angle Glaucoma

Abstract

Abstract: : Purpose: To assess the effects of brimonidine versus timolol on retrobulbar hemodynamics and visual function in patients suffering from primary open angle glaucoma (POAG). Methods: All procedures were approved by an IRB, and informed consent was obtained. Fifteen patients with POAG (58.4 ± 7.2 years, 7 male, 8 female) were recruited for this double blind randomized cross–over study. All patients received a 4 week timolol (bid) run in before baseline measurements and drug therapies. Treatment regimes consisted of 8 weeks of 0.2% brimonidine (tid) or continuation of 0.5% timolol (bid) and placebo (qd) for 8 weeks. Color Doppler imaging (CDI) using a Siemens Quantum 2000 (Siemens Quantum, Inc., Issaquah WA) with a 7.5 MHz linear probe was performed in a randomly chosen eye. Retrobulbar flow was assessed by measuring the peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) of the short posterior temporal and nasal ciliary arteries (PCA), ophthalmic artery (OA), and central retinal artery (CRA). Contrast sensitivity (CS) was measured using a rear–illuminated CS chart (CSV 1000). Linear regression analysis was used to determine the correlation between retrobulbar blood flow and contrast sensitivity. Results: As OA PSV and EDV blood flow measures improved, CS improved (p=0.008, r²=0.48 and r² =0.49, p=0.008, respectively). Accordingly, a negative correlation was found between increased OA resistance measured by RI and decreased contrast sensitivity (r²=0.423, p=0.016). Conclusions: A significant correlation between ophthalmic artery hemodynamics and CS was demonstrated in POAG patients. This suggests a possible association of retrobulbar hemodynamics with visual function.

Keywords: contrast sensitivity • visual acuity • blood supply