Laser Doppler velocimetry in retinal arteries of infants

The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (f_max) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1–f_max.dia/f_max.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of f_max. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.