Conditions: Glaucoma; Drugs Normal Tension Glaucoma Primary Open-angle Glaucoma
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 35
Healthy volunteers: no

Brief summary:
This study evaluates the possible acute changes in peripapillary blood flow after instillation of antiglaucoma medications in patients with primary open angle glaucoma (POAG), normal tension glaucoma (NTG), or ocular hypertension (OHTN) using Optical Coherence Tomography (OCT) angiography.

Detailed description:
Reduction of intraocular pressure (IOP) with topical antihypertensive medications is the mainstay of initial treatment in patients with OHTN, POAG, and NTG. Many patients, however, continue to experience disease progression despite IOP reduction. Alternative mechanisms of neurodegeneration, including vascular dysregulation and structural susceptibility of the lamina cribrosa, have been proposed as important mechanisms in progression, particularly in cases of NTG.

Prior studies have also found decreased calculated mean ocular perfusion with the use of timolol compared to other antiglaucoma medications in patients with normal tension glaucoma. Visual field deterioration has also been shown to be associated with systemic nocturnal arterial hypotension in patients with NTG, POAG, and after anterior ischemic optic neuropathy. The use of ophthalmic topical beta-blockers has been shown to lower nocturnal diastolic blood pressure and heart rate. Thus, topical beta blockers are often avoided in the treatment of NTG due to the potential risk of reduced optic nerve head perfusion

Studies evaluating optic nerve head (ONH) perfusion are limited. Earlier studies evaluated indirect measurements, such as calculated mean ocular perfusion pressure or systemic hypotension, as indications of optic nerve hypoperfusion. Direct measurements of ocular perfusion have been attempted using retrobulbar color Doppler imaging, which demonstrated decreased short posterior ciliary artery flow velocity in patients with glaucomatous visual field progression. This technique, however, has yielded inconsistent results in other studies, and is only capable of detecting gross changes to ocular blood flow.

Optical Coherence Tomography Angiography (OCTA) is a novel technique first introduced in 2014 using a custom swept-source OCT system.No studies currently exist to evaluate the effects of antiglaucoma medications on peripapillary blood flow using OCTA.

Arms:
arm 1: Timolol maleate 0.5% ophthalmic solution Instillation of one drop in each eye, once. arm 2: Brimonidine tartrate 0.2% Instillation of one drop in each eye, once.

Interventions: intervention 1: Timolol Maleate intervention 2: Brimonidine Tartrate
Intervention descriptions: intervention 1: Instillation of one drop in each eye, one-time. Obtaining of OCT angiography scans after 2 hours of instillation. intervention 2: Instillation of one drop in each eye, one-time. Obtaining of OCT angiography scans after 2 hours of instillation.

Protocol document:
Prot_SAP_000.pdf: