Objective: To determine the effectiveness of a low-dose intravitreal injection of autologous plasmin enzyme (APE), without the performance of a vitrectomy, as a treatment for refractory diffuse diabetic macular edema (DDME).
Design: Prospective, comparative, interventional case series.
Patients: Sixteen patients with bilateral DDME who had not responded to prior laser photocoagulation. All patients received an injection in 1 eye, while the other eye served as a control.
Intervention: Intravitreal 0.2 mL APE injection under topical anesthesia. The APE was obtained using a simplified method.
Main outcome measures: Central macular thickness (CMT) at 1 and 6 months, determined by optical coherence tomography (OCT) and best corrected visual acuity (BCVA).
Results: All patients underwent a 1-month follow-up. Prior to injection, CMT in the eye about to receive the injection was 541 +/- 79 microm (mean +/- standard deviation [SD]) versus 535 +/- 76 microm in the control eye. One month after injection, CMT was 241 +/- 47 microm in injected eyes and 530 +/- 85 microm in control eyes (P < 0.001, bilateral Wilcoxon test for paired samples). The macular edema (ME) improved in all injected eyes (100%), with complete resolution in 7 patients (44%). The mean BCVA of treated eyes was 0.618 +/- 0.27 (mean +/- SD) at baseline and 0.45 +/- 0.24 four weeks after injection (paired samples t-test, P < 0.001). No adverse effects were observed in any of the patients. BCVA and CMT were stable when evaluated at 6-month follow-up (0.43 +/- 0.242 and 244 +/- 46 microm, respectively).
Conclusions: Intravitreal APE injection effectively reduces macular thickening due to DDME in cases that fail to respond to conventional laser photocoagulation, and improves visual acuity in a short term, and this results remain stable in a medium term what is very important. Further investigation is warranted in order to assess long-term efficacy and safety.