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Unlabelled: A new instrument for the measurement of choroidal blood flow in the fovea is presented. It is based on the laser Doppler method and a confocal optical system with an indirect detection of the Doppler shifted light., Method: The intensity of the laser beam (785 nm) at the cornea is 90 microW. Measurements were obtained from a normal population of 21 subjects under resting conditions without dilating the pupil., Results: The reproducibility of the choroidal blood flow, based on 5 measurements of 10 s each in 5 randomly selected subjects, is 9%. The minimum detectable change for a statistical significance of p < or = 0.05, based on a population of 21 subjects and 10 s measurements, is 9%., Conclusion: This new compact instrument appears to be suitable for the investigation of the physiology and pharmacology of choroidal blood flow and the effect of age-related macular degeneration.

The structure of arteries changes with age. Gradual disappearance of elastic fibres facilitates dilatation of the arterial lumen and increase in length of the vessels. Simultaneously, the arterial wall becomes thicker, but it is often difficult to distinguish the changes due to ageing from those caused by atherosclerosis. These structural alterations result in a greater rigidity of the arteries, which can now be evaluated by non-invasive segmental methods. This shows that ageing does not have the same functional effects on wide-caliber elastic arteries and on middle-sized muscular arteries. The increase of systolic arterial pressure observed in the elderly is a consequence of structural and functional changes in the arterial system.

The aim of this study was to assess the intra-observer reproducibility at short and medium term of three non-invasive methods of arterial measurement: in the same day eight volunteers underwent five successive measurements of brachial artery diameter by two dimensional pulsed Doppler of the carotido-femoral pulse wave velocity by a piezoelectric transducer. The measurements were repeated three times at two weeks' interval. The short term (same day) and medium term (after several weeks) reproducibility of the first two methods of measurement was good: 4.69 +/- 2.37%/4.24 +/- 1.90% and 4.09 +/- 1.16%/5.02 +/- 1.71% respectively for brachial artery diameter and carotido-femoral pulse wave velocity. The reproducibility of the method of measuring digital pulse wave velocity was 10.64 +/- 3.50%/11.62 +/- 4.25%, confirming the greater variability of this parameter. Our results with these noninvasive techniques indicate that they may be used to study the arterial system and could be clinically useful in the surveillance of hypertensive patients.