Pascal Tonometry: Ocular Pulse Amplitude As It Relates To Mean Ocular Perfusion Pressure.

Purpose: To investigate the validity of the ocular pulse amplitude (OPAl using the Pascal dynamic contour tonometer (DCT) in a healthy population. Previous studies, considered the choroidal perfusion, which is indirectly measured by OP A, as a method that could be established as an independent risk factor in primary open angle glaucoma (POAG). Pulsatile blood flow into the eye causes a rhythmic fluctuation of the steady-state intraocular pressure (lOP). Ocular pulse measurements primarily reflect the difference between the systolic and diastolic blood pressure in the choroidal vascular bed. Methods. Twenty five young healthy subjects were recruited for participation. Both eyes were selected for measurement of data. The study was approved by the Human Subjects Review Committee at Ferris State University. OPA and lOP was measured using the Pascal DCT. MOPP was obtained using the formula, MOPP = 2/3 [DBP + 1/3 (SBPDBP)]
-lOP, from Sehi, et al. The subjects' systolic and diastolic blood pressures were measured on the left arm, using the sphygmomanometer. The lOP used to calculate MOPP was measured by Goldmann applanation tonometry (GAT). Results. Pearson's correlation coefficient of OPA and MOPP, which was R =0.231, was determined. It shows a low positive correlation and is not statistically significant. According to both Pearson's correlation coefficient and the paired samples t-test, there was a moderate positive correlation between GAT lOP and DCT lOP. However, despite the statistical significance (R = 0.492), there is a statistically significant difference in their means (P =0.032). This suggests that DCT data is not interchangeable to the GAT data, and one measurement cannot substitute for the other.
Conclusion. Overall, the results from this study have provided additional evidence that OP A cannot be considered an independent risk factor for glaucoma, such that there is no relationship between the OPA value and the MOPP in a normal population.