Purpose: The authors quantified the vascular resistance for venous outflow in central retinal vein occlusion (CRVO).
Methods: The blood velocity in the central retinal vein (CRV) and central retinal artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe), and 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 CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were measured simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in 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 index R' for the retinal outflow resistance was calculated by R' = deltaIOP/deltaVcrv. The authors examined 23 eyes of 23 patients with CRVO not older than 2 weeks and 23 eyes of 23 age-matched controls. There was no significant difference between the mean age of the control group (46 +/- 16 years) and that of the CRVO group (54 +/- 20 years).
Results: In eyes with CRVO, the authors found significantly lower systolic, diastolic, and mean outflow velocity. The amplitude of the CRV velocity pulse was significantly decreased compared with control eyes. In CRVO, the mean CRV velocity pulse amplitude (deltaVvein) was 1.77 +/- 1.0 cm/second, and in controls, it was 2.08 +/- 0.61 cm/second (P < 0.005). There was no significant difference in the mean IOP, but the IOP pulse amplitude (deltaIOP) was significantly higher in CRVO compared with controls (deltaIOP: CRVO 2.82 +/- 1.45 mmHg, control 1.96 +/- 0.56 mmHg, P < 0.005). The relative resistance index R' for venous outflow was significantly increased in eyes with CRVO (2.0 +/- 1.1 mmHg/cm/sec) compared with controls (1.1 +/- 0.44 mmHg/cm/s, P < 0.001).
Conclusion: In eyes with CRVO, the systolic, diastolic, and mean velocity and the amplitude of the CRV velocity-pulse curve were significantly decreased and the resistance for retinal venous outflow was significantly increased compared with controls.