Effects of Dorzolamide and Timolol on Optic Nerve Head Blood Flow Assessed With the HRF – Comparison of Data Evaluation

Abstract

Abstract: : Purpose: Several techniques to evaluate data as obtained with the Heidelberg Retina Flowmeter (HRF) were proposed. The aim of the present study was to compare the standard procedure used by Heidelberg Engineering with the recently described AFFPIA algorithm for automatic evaluation of data on a set of HRF images taken in a clinical trial comparing the effects of dorzolamide and timolol on ocular blood flow. Methods: In 140 patients with either primary open angle glaucoma or ocular hypertension the effect of a 6 months treatment period of dorzolamide versus timolol on ocular hemodynamic parameters was studied. The design of the trial was randomized (1:1), double–masked in two parallel groups. Blood flow in the rim of the optic nerve head was measured with scanning laser Doppler flowmetry using the HRF. Data were evaluated by either using a 20x20 pixel area at the neuroretinal rim and applying the standard software or by using the AFFPIA algorithm and automatic data evaluation. Results: With both methods for evaluating HRF data at the neuroretinal rim a significant difference between effects of dorzolamide and timolol was observed (p < 0.001 each). Using the conventional algorithm the effect of timolol was +1.2 ± 1.5% and using the AFFPIA algorithm the effect was –0.2 ± 1.7%. The effect of dorzolamide was +8.5 ± 1.6% and 10.9 ± 1.7% with the conventional and AFFPIA algorithm, respectively. Conclusions: In the data of a clinical trial comparing the effect of dorzolamide and timolol on ocular blood flow both algorithms employed were capable of detecting differences between dorzolamide and timolol. This indicates that the conventional and the AFFPIA algorithm provide consistent results.

Keywords: blood supply • optic disc • clinical (human) or epidemiologic studies: systems/equipment/techniques