Effect of brimonidine on retinal vascular autoregulation and short-term visual function in normal tension glaucoma

Abstract

Purpose: To assess whether brimonidine 0.15% alters retinal vascular autoregulation and short-term visual function in normal tension glaucoma patients who demonstrate retinal vascular dysregulation.

Design: Nonrandomized clinical trial.

Methods: In this prospective study, 46 normal tension glaucoma patients not previously treated with brimonidine underwent retinal vascular autoregulation testing and visual function assessment using frequency doubling technology perimetry and equivalent noise motion sensitivity testing. We measured blood flow in a major temporal retinal artery with subjects seated and then while reclined for 30 minutes. Patients having a change in retinal blood flow with posture change outside the range previously found in healthy subjects were classified as having retinal vascular dysregulation. They were treated with brimonidine 0.15% for 8 weeks and designated for retesting.

Results: Twenty-three patients demonstrated retinal vascular dysregulation at the initial visit. Younger age (P = .050) and diabetes (P = .055) were marginally significant risk factors for retinal vascular dysregulation. After the 8-week course with brimonidine, 14 of the 17 patients who completed the study showed a return of posture-induced retinal blood flow changes to levels consistent with normal retinal vascular autoregulation (P < .0001). We found no significant changes in frequency doubling technology perimetry or in motion detection parameters following treatment with brimondine (P > .09 for all tests performed).

Conclusions: Brimonidine significantly improved impaired retinal vascular autoregulation in normal tension glaucoma patients, but short-term alteration in visual function could not be demonstrated.

Trial registration: ClinicalTrials.gov NCT01105065.

Copyright © 2014 Elsevier Inc. All rights reserved.

Figures

FIGURE 1.

Motion sensitivity in patients with normal tension glaucoma. Box plots of the logarithm of the internal noise parameter measured following 8 weeks of treatment with brimonidine 0.15% 3 times a day in both eyes minus the logarithm of that measured before brimonidine treatment in the foveal area, the parafoveal inferior visual field, and the parafoveal superior visual field in patients with normal tension glaucoma. Horizontal lines, bottom to top: 25th, 50th (median), and 75th percentiles. Upper and lower vertical lines indicate data within1.5 IQR (interquartile range) of the upper and lower quartiles. Data outside these ranges are plotted as points.

FIGURE 2.

Motion sensitivity in patients with normal tension glaucoma. Box plots of the logarithm of the sampling efficiency parameter measured following 8 weeks of treatment with brimonidine 0.15% 3 times a day in both eyes minus the logarithm of that measured before brimonidine treatment in the foveal area, the parafoveal inferior visual field, and the parafoveal superior visual field in patients with normal tension glaucoma. Horizontal lines, bottom to top: 25th, 50th (median), and 75th percentiles. Upper and lower vertical lines indicate data within1.5 IQR (interquartile range) of the upper and lower quartiles. Data outside these ranges are plotted as points.