Retinal Arteriolar Vascular Reactivity in Untreated and Progressive Primary Open-Angle Glaucoma

Abstract

Purpose. To determine (1) the magnitude of retinal arteriolar vascular reactivity to normoxic hypercapnia in patients with untreated primary open-angle glaucoma (uPOAG) or progressive (p)POAG and in control subjects and (2) the effect of treatment with 2% dorzolamide on retinal vascular reactivity in uPOAG. Methods. The sample comprised 11 patients with uPOAG (after undergoing treatment, they became treated (t)POAG), 17 patients with pPOAG (i.e., manifesting optic disc hemorrhage), and 17 age-similar control subjects. The partial pressure of end-tidal CO(2) (PetCO(2)) was stabilized at 38 mm Hg at baseline. After baseline (10 minutes), normoxic hypercapnia was then induced (15 minutes) with an automated gas flow controller. Retinal arteriolar and optic nerve head (ONH) blood hemodynamics were assessed. The procedures were repeated after treatment with 2% dorzolamide for 2 weeks in tPOAG. Results. Baseline arteriolar hemodynamics were not different across the groups. In control subjects, diameter, velocity, and flow increased (P < 0.001) in response to normoxic hypercapnia. There was no change in all three hemodynamic parameters to normoxic hypercapnia in uPOAG, whereas only blood flow increased (P = 0.030) in pPOAG. Vascular reactivity was decreased in uPOAG and pPOAG patients compared with that in control subjects. After treatment with topical 2% dorzolamide for 2 weeks, the tPOAG group showed an increase in diameter, velocity, and flow (P </= 0.04) in response to normoxic hypercapnia. Similar trends were noted for ONH vascular reactivity. Conclusions. A reduced magnitude of arteriolar vascular reactivity in response to normoxic hypercapnia was shown in uPOAG and in pPOAG. Vascular reactivity improved after dorzolamide treatment in POAG.

Effect of Brimonidine on Retinal Blood Flow Autoregulation in Primary Open-Angle Glaucoma

“…We cannot rule out, however, that other topical agents may also improve retinal vascular autoregulaton. Venkataraman et al 48 have reported an improvement in retinal vascular reactivity to hypercapnia after dorzolamide treatment in patients with POAG. It is our intention is to conduct a prospective study of the effect of brimonidine as well as other topical agents on retinal vascular autoregulation in POAG patients.…”

Glaucoma and ocular blood flow: an anatomical perspective

“…Moreover, patients with glaucoma have faulty autoregulation in response to the lowering of IOP [111]. A study looking at ONH vascular reactivity to normoxic hypercapnia showed that patients with untreated POAG had reduced vascular Review reactivity to healthy controls, thus supporting the concept of vascular dysregulation in glaucoma [112].…”

Farbduplexsonographie der retrobulbären Gefäße und Hyperkapnie bei Normaldruckglaukom

“…Sines et al [27] berichteten über einen Anstieg der EDV der A. centralis retinae unter Hyperkapnie bei Patienten mit POWG, während die Blutfließgeschwindigkeiten der A. ophthalmica sogar sanken. Venkataraman et al [28] fanden hingegen eine verminderte Antwort der retinalen Gefäße und der Perfusion des Sehnervs mithilfe der Laserdoppler-Flowmetrie bei Patienten mit unbehandeltem und fortschreitendem POWG unter Hyperkapnie. Dies wurde analog zu den hier vorgestellten Ergebnissen als verminderte vaskuläre Reaktivität dieser Patienten interpretiert.…”