INCREASED VASCULAR-RESISTANCE FOR VENOUS OUTFLOW IN CENTRAL RETINAL VEIN OCCLUSION

Purpose: The authors quantified the vascular resistance for venous out flow in central retinal vein occlusion (CRVO). Methods: The blood velo city in the central retinal vein (CRV) and central retinal artery (CRA ) was measured by pulsed Doppler sonography (4-Mhz probe), and the pul se curve of the intraocular pressure (IOP) was evaluated by pneumotono metry. With multichannel data acquisition and storage software, the ve locity-pulse curve of the CRV and CRA, the IOP-pulse curve, the arteri al blood pressure, and the electrocardiogram were measured simultaneou sly in real-time mode. The relationships between the pulse curves of t he blood velocity in the CRV and CRA and the IOP were calculated off-l ine. The onset time, the time of half maximum, and the time to the max imum of the pulse curves were evaluated. A relative index R' for the r etinal outflow resistance was calculated by R' = Delta IOP/Delta V-crv . 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 signific ant difference between the mean age of the control group (46 +/- 16 ye ars) and that of the CRVO group (54 +/- 20 years). Results: In eyes wi th CRVO, the authors found significantly lower systolic, diastolic, an d mean outflow velocity. The amplitude of the CRV velocity pulse was s ignificantly decreased compared with control eyes. In CRVO, the mean C RV velocity pulse amplitude (Delta V-vein) was 1.77 +/- 1.0 cm/second, and in controls, it was 2.08 +/- 0.61 cm/second (P < 0.005). There wa s no significant difference in the mean IOP, but the IOP pulse amplitu de (Delta IOP) was significantly higher in CRVO compared with controls (Delta IOP: CRVO 2.82 +/- 1.45 mmHg, control 1.96 +/- 0.56 mmHg, P < 0.005). The relative resistance index R' for venous outflow was signif icantly 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 eye s with CRVO, the systolic, diastolic, and mean velocity and the amplit ude of the CRV velocity-pulse curve were significantly decreased and t he resistance for retinal venous outflow was significantly increased c ompared with controls.