Intravitreal thrombin activity is elevated in retinal vein occlusion.

To evaluate whether intravitreal thrombin activity is elevated in eyes with branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO) in comparison to healthy controls. Prospective clinical case series of 19 patients with BRVO, 13 patients suffering from CRVO and nine participants serving as controls. Vitreous taps were extracted from the central vitreous body, 200 μl frozen/thawed sample was immediately stabilized with 200 μl 5% human albumin, and 200 μl mixture thereof was stabilized with 200 μl 2.5 mol/l arginine, pH 8.6. Thrombin activity was determined chromogenically. Intravitreal levels of vascular endothelial growth factor (VEGF) as a marker for blood-retina barrier (BRB) breakdown were measured by a commercial chemiluminescent enzyme immuno assay (R&D). Intravitreal thrombin activity and VEGF levels were 1.6 ± 1.2 mIU/ml (mean value ± SD; range: 0.2-4.2 mIU/ml) and 554 ± 568 pg/ml (range: 20-2005 pg/ml) in BRVO-affected eyes, 2.6 ± 1.2 mIU/ml (range: 0.8-5.2 mIU/ml) and 1332 ± 1350 pg/ml (range: 58-3943 pg/ml) in eyes suffering from CRVO as well as 0.8 ± 0.8 mIU/ml (range: 0.2-2.7 mIU/ml) and 115 ± 120 pg/ml (range: 32-431 pg/ml) in controls. There are significant differences of intravitreal thrombin activity and intravitreal VEGF levels between eyes with BRVO, CRVO, and controls (P = 0.007 and P = 0.003, Kruskal-Wallis test). Intravitreal thrombin activity is significantly correlated with intravitreal VEGF levels (r = 0656; P < 0.001, Pearson correlation). Intravitreal thrombin activity might serve as a new marker for BRB breakdown or macular fibrin deposition in ophthalmology. Significant differences of intravitreal thrombin activity between eyes with BRVO, CRVO, and healthy controls might offer new therapeutic strategies for RVO-affected eyes. The effect of oral and intravitrealy injected direct thrombin inhibitors needs to be evaluated in further investigations.