Peripapillary Blood Flow After Use of Anti-glaucoma Medications: An OCT Angiography Study
Condition: Glaucoma; Drugs; Normal Tension Glaucoma; Primary Open-angle Glaucoma
MeSH terms: Glaucoma; Glaucoma, Open-Angle; Low Tension Glaucoma
Study type: Interventional
Phase: Phase 4

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.
    

Intervention name(s): Timolol Maleate; Brimonidine Tartrate
Intervention type(s): Drug; Drug
Intervention description(s): Instillation of one drop in each eye, one-time. Obtaining of OCT angiography scans after 2 hours of instillation.; Instillation of one drop in each eye, one-time. Obtaining of OCT angiography scans after 2 hours of instillation.
Other intervention name(s): Timolol; Brimonidine
Intervention MeSH terms: Timolol; Brimonidine Tartrate
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Diagnostic