Effect of isovolemic hemodilution in central retinal vein occlusion

Hemorheologic abnormalities have recently been shown to play a role in the pathogenesis of retinal vein occlusion (RVO), and several studies have demonstrated the efficacy of isovolemic hemodilution in these eyes. This study was designed to investigate further the effects of hemodilution, with regard to the duration of symptoms before the treatment.

In a prospective study, 142 eyes with central or hemicentral RVO were treated by isovolemic hemodilution. The target hematocrit value was 35%. Mean duration of follow-up was 10 months. A subgroup of 50 patients treated within 2 weeks of the onset of symptoms was compared first with patients treated later by hemodilution, and then retrospectively with controls with central RVO and without hemodilution.

Hemodilution therapy resulted in a decrease in hematocrit level from 42% to 32% on average, with no major side effect. After treatment, a significant decrease was observed in hemorheologic parameters (fibrinogen, erythrocyte aggregation), except in plasma viscosity. Retinal circulation times were significantly shortened. Visual acuity (VA) improvement immediately after treatment (in 43% of eyes) was correlated with better final visual outcome (P<0.05). At the end of follow-up, VA was better in patients treated within the first 2 weeks than in those treated later and in controls (41% had VA of 20/40 or more in the early-treatment group versus 23% in the late-treatment group, P<0.01). Final retinal ischemia was also greater in the late-treatment group and in controls. Hemodilution in 12 patients with long-standing RVO and macular edema was ineffective.

Our study is consistent with previous investigations that confirmed the efficacy of isovolemic hemodilution in RVO on hemorheologic parameters, retinal circulation times and final VA. It also underlined strongly the benefit of early treatment within the first 2 weeks of the RVO. Further studies are required to confirm these results.