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 (O 2 S) 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 (aO 2 S), venous (vO 2 S) and arterio-venous difference (AVdO 2 S) 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 vO 2 S 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 AVdO 2 S (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 aO 2 S. However, mild correlation between BCVA and both vO 2 S and AVdO 2 S ( r  = −0.2 p  = 0.035 and r  = 0.185 p  = 0.05 respectively) was found. No correlation was found between CRT and aO 2 S, vO 2 S, or AVdO 2 S. Conclusions During DME treatment with fixed regimen of intravitreal aflibercept over 11 months, we observed a reduction of vO 2 S and increase of AVdO 2 S which correlated with BCVA but not CRT. This could be explained by increasing consumption of O 2 S in the central retina and, possibly, by re-perfusion process.