Role of haemorheological factors in patients with retinal vein occlusion (original) (raw)

Increased red blood cell aggregation in retinal vein occlusion

British Journal of Haematology, 1990

Reversible aggregation of red blood cells (RBC) plays an important role in determining the flow properties of blood, and is the cause of the increase in blood viscosity at low shear rates. Retinal venous circulation is characterized by the combination of a low flow state and a high vascular resistance which might severely limit its capacity to adjust to high blood viscosity. These characteristics make the venous circulation in the retina particularly dependent on haemorheological factors. To test the possibility that high RBC aggregation could predispose to the onset and development of retinal vein occlusion (RVO), RBC aggregation and disaggregation (SEFAM erythroaggregameter, France) were measured in 64 patients with RVO. Results were compared to those of a group of 64 controls, similar in age, sex, smoking habit and associated pathologies. Increased RBC aggregation was observed in 52% of the patients, and the mean values showed a highly significant elevation of RBC aggregation parameters in RVO patients (+14%) when compared with controls (P less than 0.001). Subgroups were compared to study the influence of site (central versus branch), form (ischaemic versus non-ischaemic), duration and severity of the occlusion on the aggregation parameters. No significant differences were found between these various subgroups. An increase in RBC aggregability and in the shear resistance of RBC aggregates, by predisposing to circulatory stasis, is likely to contribute to the onset of RVO.

Fibrinolytic activity in retinal vein occlusion

International Ophthalmology, 1997

Purpose: Impaired fibrinolytic function is a common finding in patients with thrombotic disease. The present study was initiated to evaluate the fibrinolytic response to a venous occlusion test (VOT) in patients with retinal vein occlusion. Methods: Euglobulin clot lysis time (ECLT), tissue plasminogen activator (t-PA) activity, and plasminogen activator inhibitor (PAI) activity were measured before and after VOT in a group of 26 consecutive patients presenting with retinal vein occlusion and in 15 healthy age- and sex-matched controls. Results: Before VOT (baseline), a higher proportion of patients (54%) had an ECLT of more than 5 h compared with controls (6.7%)(p = 0.0027) indicating decreased overall fibrinolytic activity. Patients had non-significantly lower t-PA and higher PAI activities compared with controls. After VOT, a higher proportion of patients (34.6%) had an ECLT of more than 5 h compared with controls (6.7%) (p = 0.05). Patients had significantly lower t-PA activity (p = 0.0232) and significantly higher PAI activity (p = 0.0292).Subgroup analysis revealed that patients with an ECLT of more than 5 h had significantly higher levels of PAI activity at baseline (p =0.0326) and after VOT (p = 0.0184) compared with patients with an ECLT of less than 5 hours. However, t-PA activity was significantly higher(p = 0.0153) at baseline, and non-significantly higher after VOT in patients with an ECLT of more than 5 h when compared with patients with an ECLT of less than 5 hours. Conclusions: These findings suggest that impaired fibrinolysis due to increased PAI activity may play a role in the pathogenesis of retinal vein occlusion.