Tip of the Month
Publishing date: June 2012
Tip Editors: Ann Hoste, John Salmon and John Thygesen
Tip reviewer: Roger Hitchings
The Science behind the Tip
A recent study has shown that visual function is more likely to be preserved with brimonidine 2% than with timolol 0.5% in patients with normal tension glaucoma despite similar intraocular pressure lowering effects (1).
The problem with brimonidine is a significant incidence of ocular allergy, 20.2% at one year (1) increasing to 32.3% after several years (2).
The beneficial effect of brimonidine is presumably the consequence of neuroprotection, mediated by an interaction with alpha2-adrenergic receptors in the retinal ganglion cells. Although the exact mechanism is not fully understood, there is experimental evidence in the rat model to support this hypothesis (3). It is unlikely that a change in diastolic perfusion pressure is responsible for the difference between brimonidine and timolol (4).
Contributor: John Salmon, Oxford
1. Krupin T, Liebmann J, Greenfield DC, et al. A randomised trial of brimonidine versus timolol in preserving visual function: results from the Low-Pressure Glaucoma Treatment Study. Am J Ophthalmol. 2011;151:671-81.
2. Rahman MQ, Ramaesh K, Montgomery DM. Brimonidine for glaucoma. Expert Opin Drug Saf. 2010;9:483-91.
3. Wheeler L, WoldeMussie E, Lai R. Role of alpha-2 agonists in neuroprotection. Surv Ophthalmol. 2003;48:S47-51.
4. Quaranta L, Gandolfo F, Turano R, et al. Effects of topical hypotensive drugs on circadian IOP, blood pressure and calculated diastolic ocular perfusion pressure in patients with glaucoma. Invest Ophthalmol Vis Sci. 2006; 47:2917-23.