Vitreal Erythropoietin Is Elevated Following Retinal Vein Occlusion Independent Of Serum Levels

Abstract

Purpose: : Erythropoietin (Epo) is a bone-marrow derived molecule that is induced by low hematocrit (Hct). Beyond its role in erythropoesis, Epo has been found to be elevated in vitreous samples from patients with proliferative diabetic retinopathy. In this study we asked (i) if vitreal Epo is elevated in patients with retinal vein occlusion (RVO) and (ii) if isovolemic hemodilution therapy (IHT) after RVO increases Epo levels by lowering Hct values.

Methods: : In a first cohort of 10 patients with early RVO we measured serum Epo levels before, during and after IHT. In a second cohort of 12 controls and 12 RVO patients we measured serum and vitreal Epo levels and correlated them with IHT, duration of occlusion, visual acuity, central macular edema (CME) and vitreal VEGF levels.

Results: : In the first cohort, Epo serum levels increased with the number of hemodilutions (r = 0.88) while Hct decreased (r = 0.78). After a mean of 2.1 hemodilutions, Epo serum levels differed significantly from control patients (p = 0.01). In the second cohort, vitreal Epo levels in all patients (controls and RVOs) were significantly higher than Epo serum levels. Vitreal Epo differed significantly between controls (average: 35,5 mU/ml) and RVO patients (average: 137,2 mU/ml, p = 0.0005) and showed a positive correlation with vitreal VEGF levels (r=0,64) and CME thickness (r=0,66) but not with serum Epo levels (r = 0.23).

Conclusions: : Serum Epo levels increase during IHT in RVO patients. However, serum Epo does not correlate with vitreal Epo levels which are several orders of magnitude higher and increased in RVO patients vs. controls. These findings indicate a local production of Epo in the eye that is increased following RVO. IHT does not - positively or negatively - alter these elevated vitreal Epo levels in RVO patients.

Keywords: retina • vitreous