Influence of betaxolol and timolol on the venous tone in glaucoma patients

The aim of this study was the assessment of physiological venous reflexes in 40 glaucoma patients treated with topically applied timolol maleate 0.50% and betaxolol HCL 0.50%. They were divided into two groups of twenty each; one group being given timolol and the other betaxolol. The assessment of the venous tone was performed by testing venous reflexes. We found no statistically significant difference between timolol and betaxolol; however, when the influence of circulating catecholamines and the other vasoactive substances was excluded by suprasphygmatic insufflation of a pediatric cuff, a significant difference was found in the Valsalva's maneuver (125.5 +/- 8.1 vs 85.0 +/- 34.3 venoconstrictive units VCUs, p = 0.03). The IOP was significantly decreased in both treatment group, although the pressure reduction effect was more pronounced in the timolol group. Our study suggests that timolol and betaxolol have a slightly different mode of action on the venous side of circulation under topical medications. It is possible that the use of betaxolol topically may reduce a systemic venoconstriction.