Peripapillary Blood Flow After Use of Anti-glaucoma Medications: An OCT Angiography Study

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.

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.

Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of ocular hypertension, primary open angle glaucoma, or normal tension glaucoma in the study eye(s)
* Age 18-90
* Best corrected visual acuity of 20/60 or better

Exclusion Criteria:

* Current use of either brimonidine or timolol
* Other disease, ophthalmic or systemic, that is likely to significantly affect the OCT test in the study eye(s) including:

  * More than moderate grade cataract that significantly reducing OCTA scan signal level
  * Macular degeneration other than mild drusen or pigmentary changes
  * Diabetic retinopathy other than mild background non proliferative retinopathy
  * Prior or current macular edema
  * Prior laser treatment to the retina
  * Prior retinal detachment
  * Prior central serous retinopathy
  * Prior retinal vein or artery occlusion
  * Prior inflammatory retinopathy or choroidopathy
  * Keratoconus or other corneal ectasia
  * Corneal scarring in central 4 mm
  * Prior penetrating keratoplasty
  * Ischemic optic neuropathy
  * Dementia beyond early/mild memory loss
  * History of cerebrovascular accident
  * History of severe carotid stenosis
  * History of previous ocular surgery other than non-complicated cataract extraction