Abstract
Purpose::
Image analysis by the Retinal Vessel Analyser (RVA) observes vessels in their dynamic state online non-invasively along a chosen vessel segment. Longitudinal vessel diameter profiles can be determined. Previously we found that the roughness (high-frequency diameter changes) along longitudinal vessel profiles increases significantly in anamnestically healthy volunteers with increasing age and in glaucoma patients during vascular dilation. This might be an expression of endothelial damage. Whether longitudinal retinal arterial profiles in systemic hypertension are altered is investigated here.
Methods::
15 untreated patients with systemic hypertension (age 50.9+11.9 years) and 15 age matched anamnestically healthy volunteers were examined by RVA (IMEDOS, Jena, Germany). After baseline assessment for 1 min a monochromatic (530-600nm) rectangular luminance flicker of 12.5 Hz was applied for 20 sec. In arterial segments of approximately 1 mm in length vessel diameters were measured in order to obtain a longitudinal vessel profile. Differences in amplitude and frequency of vessel diameter change were analysed using Fourier transformation.
Results::
Power spectra of healthy subjects do not change significantly during all stages of the arterial response to flicker stimulation: longitudinal arterial diameter profiles show mainly low frequency waves with a period of 480-625 microns (one peak). In hypertensive patients the power spectrum demonstrated two peaks with low frequency waves with a period of 310 microns and mid frequency waves with a period of 225 microns at baseline, constriction and relaxation phases of the reaction to flicker with a significant difference to healthy subjects (p<0.05). Low frequency waves with a mean period of 550 microns are characterising the longitudinal arterial diameter profiles in hypertensive patients during dilation. This is significantly different to baseline in hypertensive patients (p<0.05).
Conclusions::
Retinal arteries possess alternating vessel diameters which constitute the vessel longitudinal section profile. Microstructural changes in longitudinal profiles of retinal arteries in patients with systemic hypertension might be an indication for alterations in the vascular endothelium and smooth muscle cells in this disease, leading to impaired perfusion and regulation.
Keywords: imaging/image analysis: clinical • retina • blood supply