RETINAL VESSEL ANALYZER (RVA) - A NEW METHODW. Vilser
Vessel diameter controls blood flow, velocity and blood pressure distribution across the microcirculation network and influences substance exchange between capillaries and surrounding tissue. Retinal Vessel Analyzer (RVA) from Zeiss Jena is a new technique to analyse the behaviour of vessel diameter in dependence on time and place along the vessel.
Method: Intelligent measuring technique of RVA analyses remission profiles of vessels, finds vessels automatically, controls and corrects errors and estimates vessel diameters independent of eye movements, brightness and contrast changes in fundus pictures. Examiner chooses interesting vessel segments ( up to 2 mm length) on monitor screen. RVA takes 25 measuring values per second. Diameters are recorded and on line presented graphically in dependence on time during measurements. Local and temporal diameter changes are analysed and presented by RVA.
Results: Examinations of volunteers in different studies show local diameter changes up to 10%. Temporal changes (pulsations: 0,5-2%, vasomotions: 1-4%, circadian changes), blood pressure dependencies, and provoked vessel responses can be detected to CO2-, 02- and rebreathing, intraocular pressure and light changes on single vessel segments (depended on kind of provocation: -14 to +10% ). Diameter changes are different for place along vessel segment. In dependence on measuring conditions and medical questions detectable limits of diameter changes can amount to 1%.
Conclusion: By use of RVA there are new possibilities for studies and clinical examinations of retinal microcirculation and its control mechanisms. Especially RVA allows to get reliable information for single case, even for single vessel segments and is suitable to study individual variability of vessel responses.
Supported by TMWFK: B303-96144
Technical University llmenau, BMTI, PF 100565, D-98684 Ilmenau