Retinal blood flow in nonischemic central retinal vein occlusion.

Abstract

The authors studied the changes in retinal blood flow (RBF) and oxygen reactivity in a major temporal vein in patients with central retinal vein occlusion (CRVO). Eleven patients with nonischemic CRVO approximately 7 weeks from onset of disease. Laser Doppler velocimetric measurement of RBF and vessel reactivity to inhaling 60% oxygen. Measurements were performed at baseline and 3 months. Flow velocity in the affected eye had increased significantly by 3 months, from 1.6 +/- 0.4 cm/second to 2.0 +/- 0.4 cm/second (P = 0.02). Retinal blood flow, however, remained unchanged (13.7 +/- 5.8 microl/minute versus 15.0 +/- 6.5 microl/minute). The two comparable RBF values, despite differing velocity values, suggest that the relatively normal baseline value was achieved through higher intravascular pressure at baseline (Bernoulli's principle). This is supported by the fact that oxygen reactivity had improved from 2.1% +/- 3.6% at baseline to 3.8% +/- 3.1% (P = 0.001) at 3 months, which suggests an improved ability to respond to hyperoxia from reduced intravascular pressure. Intravascular pressure in CRVO appears to continue to decrease during the first 5 months after the onset of CRVO, indicating continuing reduction in the degree of outflow obstruction during this time.