Relationship between Ocular Pulse Pressures and Retinal Vessel Velocities

Abstract

The authors quantified the relationship between ocular pulse pressures and retinal vessel velocities. The blood velocity in the ophthalmic artery (OA), the central retinal vein (CRV), and artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe). The pulse curve of the intraocular pressure (IOP) was evaluated by pneumotonometry. With multichannel data acquisition and storage software, the velocity pulse curve of the OA, the CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were recorded simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in the OA, the CRV and CRA, and the IOP were calculated off-line. The onset time, the time of half maximum, and the time to the maximum of the pulse curves were evaluated. A relative retinal venous outflow resistance index (R') was calculated by R' = deltaIOP/deltaVcrv. We examined 23 eyes of 23 healthy subjects. The mean age of the group was 46 +/- 16 years. In all eyes, the outflow in the CRV was pulsatile and ran in synchrony with the IOP pulsation. The CRV velocity- and IOP-pulse curve showed a significant mean delay of 0.024 second compared with the CRA and OA velocity-pulse curve. The relative resistance index R' for venous outflow was 1.0 +/- 0.44 mmHg/cm/seconds. In all eyes, the authors found a significant linear relationship between the blood velocity in the CRV and the IOP pulsation. The CRV velocity- and IOP-pulse curve were significantly delayed compared with the CRA and OA velocity-pulse curve.