الفهرس 
Vascular Theory as a Pathophysiological Hypothesis in POAGOnly 14 pages are availabe for public view
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Abstract
Aim: To study the hemodynamic effects of brimonidine on optic nerve head and retinochoroidal vasculature in eyes with primary open angle glaucoma using optical coherence tomography angiography.
Design: A prospective longitudinal uncontrolled interventional study.
Patients and methods: 41 Brimonidine-naiive primary open angle glaucoma patients were recruited and started on topical brimonidine tartrate 0.2% bid as part of their ocular hypotensive glaucoma treatment (either as monotherapy or as add-on to other topical antiglaucoma for better control of IOP). All patients had a baseline OCT-A imaging prior to commencing topical brimonidine in the form of OCT-A ONH 4.5*4.5 mm and OCT-A macula 6*6 mm and then monthly imaging for 3 consecutive months thereafter in a seated position and after 20 minutes of assuming a right recumbent position. Seated and recumbent measurements of arterial blood pressure as well as IOP were also recorded for baseline and each visit thereafter.
Results: Topical brimonidine 0.2% bid was associated with a statistically significant increase in DRI (deep resistance index) P-value 0.012 as well as a decrease in SRI (superficial resistance index) which was however statistically insignificant P-value 0.409. Also, the S/D resistance ratio (superficial to deep resistance ratio) showed a statistically significant decrease P-value 0.001. Other findings were a decrease in DFI (deep flow index) P-value 0.116, an increase in the SFI (superficial flow index) P-value 0.064 and an increase in the S/D flow ratio (superficial to deep flow ratio) P-value 0.133.
Conclusion: Brimonidine showed multiple potentially beneficial long-term hemodynamic effects on the retina and ONH in patients of POAG most notably the redistribution of macular blood flow in a way that favors better perfusion of the SVP which is responsible for metabolic sustenance of GCL. This can be one of the mechanisms through which brimonidine exerts its neuroprotective action on RGCs