PI quantification in the human eye arterioles

What is it about?

The Pulsatility Index (PI) was quantified for the first time in the human conjunctival pre-capillary arterioles in vivo. In 30 arterioles with diameters ranging between 6 and 12 μm, from 15 healthy humans, peak to peak velocity ranged from 0.2 up to 4.8 mm/s with a mean value equal to 1.4 ± 0.2 (SE) mm/s. The PI ranged from 0.4 to 1.5 and the overall mean value was 0.8 ± 0.1 (SE). The linear correlation between PI and diameter was practically zero (Spearman’s correlation coefficient, rs ≈ 0) for the range of arteriolar diameters examined here. In this work, a first step was made towards the complete PI mapping of the human carotid arterial tree.

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Why is it important?

1) The normal range of RI (Resistive Index) and PI (Pulsatility Index) values is still unknown in most areas of the human body. 2) Most of the ultrasound instruments used in clinical practice estimate automatically the value of the PI. 3) The PI was quantified for the first time in the human precapillary arterioles of the eye in vivo (0.8 +/- 0.1). 4) It would be interesting to see how the normal PI value changes in pathological conditions such as carotid stenosis, sickle cell disease, ischaemic stroke or in other situations such as contact lens wearing.

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