Local Retinal Vein Reaction To Increased Intraocular Pressure In Normals And Glaucoma Patients

Abstract

Abstract: : Purpose:Glaucoma patients might display a different vessel reaction compared to normal subjects to stimuli such as short term increase of IOP. The Retinal Vessel Analyzer (RVA) allows to examine vessel reactions along a given vessel segment over time. Different behavior in each location can thus be assessed. Methods:9 untreated open angle glaucoma patients with a mean IOP of 23.3 ± 1.9 mmHg and a mean age of 55.7 ± 8.5 years and 9 age matched controls with a mean IOP of 13.7 ± 1.6 mmHg were examined. Baseline measurements with RVA were obtained for 2 minutes. IOP was artificially increased by suction cup (method described by Ulrich) to a suprasystolic level for 45 sec then suction was released. On-line RVA measurements continued during the whole experiment for a total of 10 minutes. Data was analyzed according to local retinal vein diameter changes over time along a segment of about 1.5 mm length. Results:During baseline measurements the mean differences of local vessel diameter between local maximum and minimum along retinal veins was 4.1% ± 2.4% in the glaucoma group and 7.9% ± 3.6% in normals, a statistically significant difference with p=0.02 by Mann-Whitney test. Mean dilation of vessel diameter after pressure provocation compared to baseline in the glaucoma group for local maxima amounted to 5.4% ± 4.1% (p< 0.01) and for local minima to 6.3% ± 5.0% (p< 0.01). In the group of normals dilatation after pressure provocation for local maxima amounted to 11.9% ± 5.0% (p< 0.01) and for local minima to 14.6% ± 4.0% (p< 0.01) Conclusion:Normals show more pronounced minimal and maximal diameters along retinal veins under normal circumstances than glaucoma patients. The dilatory reaction after pressure provocation is of a higher magnitude in normals than that observed in the glaucoma group. Especially the small diameter segments (minima) dilated more than the wide diameter segments (maxima) in normals while in glaucoma patients reactions were similar in small and wide diameter segments. These findings might represent an intact autoregulatory response to pressure provocation in normals and an impaired vessel reaction in the observed glaucoma population.

Keywords: 430 imaging/image analysis: clinical • 444 intraocular pressure • 554 retina