Purpose The Pascal dynamic contour tonometer (DCT) allows measurement of intraocular pressure (IOP) independently of corneal properties.
It records, simultaneously, haemodynamic IOP fluctuations and the difference between the systolic and the diastolic IOP corresponding
to the ocular pulse amplitude (OPA). The OPA indirectly reflects choroidal perfusion and could be considered as an independent
risk factor in glaucoma. We aimed to establish the physiological diurnal variability of the OPA and its correlations with
other biophysical parameters because its characteristics remain partly unclear.
Method Prospective study including 52 eyes of 28 normal subjects with Goldmann applanation tonometry (GAT) IOPs < 22 mmHg. Subjects
treated with systemic medications that could interfere with blood pressure or heart rate were excluded. IOP was measured at
9:00 am, 1:00 pm, and 4:00 pm by GAT and DCT. Two consecutive GAT followed by three consecutive DCT measurements were performed
in each session by the same clinician (SP). Only DCT measurements with quality 1 and 2 were taken into account. Blood pressure,
pulse rate, and central corneal thickness (CCT) were recorded after the last IOP measurements. Spearman correlation coefficient
was used for assessment of correlations.
Results Mean age was 40 ± 14 years. Mean DCT values were significantly higher than GAT readings (mean = 16.8 ± 2.0 vs. 15.2 ± 2.8 mmHg,
P < 0.02). The mean OPA was 2.2 ± 0.7 mmHg (range: 1–3.4 mmHg). The mean amplitude of diurnal OPA fluctuations was 0.4 mmHg.
There was no significant difference in the mean OPA values at each time of the diurnal curve. The intraclass correlation (ICC)
of only one OPA measurement in relation to part of total variance due to inter-measurement variation was 78%. Averaging over
three independent readings of OPA improved ICC to 91%. The OPA was correlated with GAT (
r = 0.31,
P < 0.0001) and DCT IOP measurements (
r = 0.49,
P < 0.0001). It was correlated neither with blood pressure nor with age. OPA values of both eyes of the same individual were
highly correlated (
r = 0.89,
P < 0.0001).
Conclusion In normal healthy eyes, the ocular pulse amplitude remains stable during normal outpatient office hours and was not correlated
with blood pressure or age of patients.
Keywords Intraocular pressure - Dynamic contour tonometry - Goldmann applanation tonometry - Ocular pulse amplitude