Abstract:
The ocular fundus offers a unique non invasive possibility to visualize vessels and their reactions to stimuli. By image analysis it is possible to perceive vessels in their dynamic state online. Vessel diameters can be characterized along a given vessel segment. Retinal vessels react to flicker stimulation. Whether there is a difference in reaction to a flicker stimulus in healthy persons of different age is investigated in our study.
10 healthy volunteers of the age group of 20–30 (25.3 +1.9) years and 60–70 (72.6+9.5) years each were examined by retinal vessel analyzer (RVA by IMEDOS, Jena, Germany). After baseline assessment for 1 minute a monochromatic (530–600nm) rectangular luminance flicker of 12.5 Hz was applied for 60 sec. In arterial segments of a length of approximately 1 mm vessel diameters were measured in order to obtain a longitudinal vessel cross section profile. Differences in amplitude and frequency of vessel widths change was characterized by the calculated parameter 'spectral edge frequency' (SEF) before during and after stimulation.
Spectral edge frequency for both age groups in measuring units–1:
SEF was statistically significantly different (p<0.05, U–test) between both examined age groups in each phase of the arterial reaction. We found no statistically significant difference within the same age group for the different phases (p>0.2).
Retinal branch vessels possess alternating vessel diameters which constitute the vessel crossectional profile. Using the retinal vessel analyzer the frequency and amplitude of diameter differences can be assessed. We describe the parameter SEF, which we termed ‘vessel thickness frequency change’. In the group of older volunteers this parameter is significantly different from younger volunteers. This means, that vessels in the elderly assume a less regular profile. We think this might be an expression of endothelial damage.
Keywords: aging • clinical (human) or epidemiologic studies: natural history • imaging/image analysis: clinical