Effect of Cosopt Versus Combigan on Retinal Vascular Autoregulation in Primary Open Angle Glaucoma (POAG)

Effect of Cosopt Versus Combigan on Retinal Vascular Autoregulation in Primary Open Angle Glaucoma (POAG)

Effect of Cosopt Versus Combigan on Retinal Vascular Autoregulation in Primary Open Angle Glaucoma (POAG)

We have completed a study in which we examined the response of the retinal circulation to changes in posture from sitting to lying down in patients with primary open angle glaucoma (POAG). This alteration in position produces changes in the local blood pressure at the entrance to the retinal vasculature. In a healthy retina, the vasculature adapts by dilating and constricting in order to maintain a steady blood flow rate. In an eye with POAG, this often does not occur. As a result, there are large fluctuations in blood flow which may produce the retinal neuronal damage associated with glaucoma. The purpose of this study is to demonstrate that topical anti-glaucoma treatments with agents that have vasoactive as well as IOP-lowering effects can have a beneficial effect on maintaining a steady retinal blood flow rate even when there are changes in local blood pressure.

Patients using timolol were switched to brimonidine tartrate / timolol maleate 0.2%/05% 1 get BID OU for six weeks.

Patients using timolol were switched ti dorzolamide hydrochloride / timolol 0.5% 2%/0.5% bid OU for six weeks

We determined whether RVD was present in the following way. The difference between the retinal blood flow measured while reclining for 30 minutes and the baseline retinal blood flow measured while seated was calculated. In a previous study, we found that among healthy subjects the change in the blood flow while reclining compared to baseline was +6.5% ± 12%. For this study, we defined the normal range of blood flow autoregulation as ± 2 standard deviations about the mean percentage change found in the control group in the initial study (6.5% ± 24.0%); that is, as -17.5% to +30.5%. Participants with a change in retinal blood flow induced by posture change outside this range were randomized to either dorzolamide-timolol fixed combination BID OU or brimonidine-timolol fixed combination BID OU for 6 weeks.

Inclusion Criteria: POAG Age 40 to 80 years Untreated IOP greater than 21 mm Hg Exclusion Criteria: More than two IOP lowering medications Exfoliation or pigment dispersion syndrome Diabetic retinopathy History of ocular surgery

Feke GT, Pasquale LR. Retinal blood flow response to posture change in glaucoma patients compared with healthy subjects. Ophthalmology. 2008 Feb;115(2):246-52. doi: 10.1016/j.ophtha.2007.04.055. Epub 2007 Aug 8.