V 291
Retinal vessel reaction to O2 breathing in branch vein occlusion patients
I. M. Lanzl 1, B. Witta 1, K. Kotliar 1, W. Vilser 2
Purpose: Healthy retinal veins constrict after O2 breathing provocation. The aim of this study was to investigate changes in the regulatory potential of retinal veins after branch vein occlusion (BRVO) using the vessel constriction after O2 breathing as a model.
Methods: 14 patients affected by unilateral branch vein occlusion were studied. The Retinal Vessel Analyzer (RVA by Imedos) was used to assess the vessel diameter in real time mode. A baseline recording was obtained for 1 minute. Recording continued during the subsequent 5 minutes of 100% O2 breathing provocation period and the ensuing 5 minutes of room air breathing. Measurements were taken in the affected eye along the affected branch vein and on the fellow eye along a corresponding venous segment.
Results: 5 minutes of O2 breathing lead to a mean constriction in the affected venous segment of 5.3 + 2.5% and to a mean constriction of 5.1 + 1.1% in the corresponding vein in the contralateral eye. The variance of the measurements was 27.6 in the BRVO eye and 14.2 in the fellow eye.
Discussion: 100% O2 breathing is a potent vasoconstrictor in healthy normal subjects. Venous vessel diameter as measured by RVA according to our previous findings in those subjects decreases around 15% after O2 provocation. In the present study the venous reaction to O2 is decreased in the diseased eye as well as in the contralateral eye. The higher variance of measurements in the BRVO eye could be explained by different regulatory mechanism trying to compensate for the insult by BRVO which eventually lead to either the ischemic or non ischemic late form of the disease. The less than expected constriction in the affected eye as well as the partner eye in comparison to normal volunteers could also be explained by a systemic affection of patients with BRVO or by generalized changes in vessel behaviour due to the ageing process. These suspected changes should be clarified in further studies.
1
Augenklinik der TU München, Ismaninger Str. 22, D-81675 München