Effect of topical betablockers on human retinal vessels diameters

Purpose: To measure the effect of topical betaxolol 0.5% and timolol 0.5% on retinal vessels diameters by means of photographic enlargment. Methods: Thirteen glaucomatous patients (primary open angle glaucoma (POAG) and ocular hypertensive (OH)) were treated twice daily with betaxolol 0.5% for one year. These same patients were subsequently treated with timolol 0.5% during the following year. Fundus photographs were taken with Canon camera 30 degrees angle at baseline and two hours after instillation at 3, 6 and 12 months of treatment for each drug. The diameters of the superior and inferior temporal vessels (arteries and veins) were measured at one and two disc radii from the margin of the disc using photographic enlargment (x 66.7) of the right eye and were analysed under double masked fashion during the same session. Results: A significant increase of the mean arterial diameter (+ 7.4% p = 0.000 paired t) was found after 12 months of betaxolol treatment, while no persistent further difference (+ 1.3% NS) was found after 12 months of timolol treatment. No modification was found in venous diameter. Conclusion: Betaxolol treatment is associated with a beneficial effect on retinal arteries width whereas Timolol does not yield the same amplitude of benefit.