Abstract
Purpose:
A reduction of the flicker response of retinal vessels in glaucoma patients after a washout period compared to controls is reported in the literature. We tested the hypothesis that local medication might influence this response. The study was done in 30 glaucoma patients and 30 age matched control subjects.
Methods:
Prospective, clinical, diagnostic study in 30 glaucoma patients under local pressure lowering solutions vs 30 control subjects: No significant differences (p>0.05): Age: 64±7 vs 65±7. Gender, m/f: 11/19 vs 13/17. OD/OS: 18/12 vs 21/9. Intraocular pressure (IOP):16±2.5 vs 16±2.9. Blood pressure: 143±18/81±9 vs 136±16/79±12. Assessment of flicker response of retinal vessels by Dynamic Vessel Analyzer (DVA) (IMEDOS, Germany) (Zeiss 450 FF Fundus camera combined with a computer for process control and signal analysis). Procedure: On the camera display a 1 mm section of an arteriole and of a venole was marked in which the diameter was continuously measured for 350s. First 50s: baseline , next 20s: flicker illumination (push-push interruption of the illumination beam, frequency 12 Hz), next 80s continuous illumination. Two times repetition of the 20 s and 80 s periods. Averaging of the three 20s and 80s periods. Static vessel analysis was done afterward. Statistics: Paired t-test and χ2-test.
Results:
Parameters are given as mean±standard deviation. Dilation in response to flicker, % of baseline diameter: Glaucoma/controls: Arteriole: 3.4±2.3/2.5±1.7 (p=0.11). Venole:4.6±2.2/3.2±1.5 (p=0.01). Static vessel analysis, diameter in µm: Central retinal artery equivalent (CRAE): 171±15/182±14 (p=o.o1). Central retinal vein equivalent. (CRVE):200±17/208±20 (p=0.12). Diameter of the vessel section measured, µm: Arteriole: 107±12/114±13 (p=0.04), venole:128±20/137±21 (p=0.09).
Conclusions:
In this study the flicker response of the vessels measured by DVA is higher in glaucoma patients than in age matched control subjects. In previous studies glaucoma patients were examined after a washout period. Their retinal vessels showed comparable baseline diameters to those of control subjects We examined patients under topical glaucoma therapy. Static vessel analysis showed narrower vessels in glaucoma patients than in controls. It may be hypothesized that narrower vessels in glaucoma patients allow a more pronounced dilation than the vessels in the control subjects.
Keywords: 468 clinical research methodology •
550 imaging/image analysis: clinical •
549 image processing