Velocity of ophthalmic arterial flow recorded by Doppler ultrasound in normal subjects.

Transcranial Doppler ultrasound (2 MHz) was used to measure ophthalmic arterial blood flow velocity in 60 normal subjects whose mean age (+/- standard deviation) was 54.9 +/- 17.3 years (30 women, mean age, 56.3 +/- 17.5 years and 30 men, mean age, 53.5 +/- 17.3 years). Three or more measurements were recorded from each eye at reference depths of 40 to 45 mm. The peak systolic flow velocity was 45.1 +/- 7.8 cm/sec, mean-enveloped flow velocity was 22.6 +/- 5.1 cm/sec, end diastolic flow velocity was 12.0 +/- 3.4 cm/sec, pulsatility index was 1.5 +/- 0.4, and resistivity index was 0.7 +/- 0.1. No significant differences of flow variables were found between genders. Statistically significant age-related losses of mean-enveloped flow velocity and end diastolic flow velocity were shown (P = .003 and .038). There were no significant differences of flow velocities between right and left eyes when comparing means. Differences greater than 20% between eyes were found in ten subjects (16.7%) for peak systolic flow velocity, in 18 subjects (30.4%) for mean-enveloped flow velocity, and in 21 subjects (34.8%) for end diastolic flow velocity, but resistivity indexes were comparable in all cases. Ten subjects had flow velocities measured at two different depths separated by 10 mm (40 to 45 mm vs 50 to 55 mm) in the same orbit and showed that peak systolic flow velocity and mean-enveloped flow velocity were significantly higher (P = .006 and .021) at the greater depth. Recognizable differences in shape of the spectrograms obtained from the younger subjects (< or = 30 years) and the older subjects (> or = 70 years) were found.