Changes of retinal oxygen saturation during treatment of diabetic macular edema with a pre-defined regimen of aflibercept: a prospective study

Abstract

Purpose: To study the effect of anti-VEGF therapy for diabetic macular edema (DME) on retinal oxygen saturation (O₂S) and its correlation with functional and anatomical changes of retinal tissue.

Methods: An interventional prospective single group study. Included were 10 eyes of 10 patients with visually significant DME which received a fixed regimen of intravitreal aflibercept every 4 weeks for 5 months, followed by 3 injections every 8 weeks, and were controlled monthly. Visual acuity (VA), central retinal thickness (CRT), arterial (aO₂S), venous (vO₂S) and arterio-venous difference (AVdO₂S) retinal oxygen saturation were noted monthly. Changes after 5th (V6) injection and on last follow-up (V12) were studied. Correlations of different parameters were analyzed.

Results: The aO2S did not change whereas vO₂S decreased (62.2 ± 9.4 pre-op to 57.2 ± 10.5 on V6, p = 0.03). This remained unchanged at 59.4 ± 13.2 on V12 (p = 0.2) and was accompanied by an increase of AVdO₂S (40.8 ± 8.3 pre-op to 44.8 ± 10.6, p = 0.03 on V6) which was followed by a non-significant decrease to 41.8 ± 11.3 on V12 (p = 0.06). We found no correlation between BCVA and aO₂S. However, mild correlation between BCVA and both vO₂S and AVdO₂S (r = -0.2 p = 0.035 and r = 0.185 p = 0.05 respectively) was found. No correlation was found between CRT and aO₂S, vO₂S, or AVdO₂S.

Conclusions: During DME treatment with fixed regimen of intravitreal aflibercept over 11 months, we observed a reduction of vO₂S and increase of AVdO₂S which correlated with BCVA but not CRT. This could be explained by increasing consumption of O₂S in the central retina and, possibly, by re-perfusion process.

Keywords: Aflibercept; Anti-VEGF therapy; Diabetic macular edema; Diabetic retinopathy; Retinal oxygen saturation.