Subtenon injection of natural leukocyte interferon α-2a in diabetic macular edema: a case report

To report the effect of subtenon injections of natural leukocyte interferon α-2a (IFNα) on best corrected visual acuity (BCVA) and central macular thickness (CMT) in a patient with diabetic macular edema (DME).

A 66-year-old man affected by DME, with glycated hemoglobin (HbA1c) at 6.9%, refractory to laser grid treatment and intravitreal injections of triamcinolone, was selected to receive a cycle of three subtenon injections/week of IFNα (1×10⁶ IU/ml). BCVA and CMT, using spectral domain ocular coherence tomography (SD-OCT), were evaluated preoperatively and at 1 week, 1 month, 4 months, and 1 year postoperatively. BCVA and CMT were significantly improved at 1 week after the three injections (20/200 vs. 20/40 and 498 μm vs. 237 μm, respectively). BCVA remained stable during the 1-year follow-up. CMT was slightly increased, but was still lower than the baseline value (215 μm, 255 μm, and 299 μm during the follow-up visits). No adverse events were recorded, with the exception of mild subconjunctival hemorrhage at the injection site.

IFNα, with its immunomodulatory, anti-proliferative and anti-angiogenic actions, was effective in improving BCVA and reducing CMT in refractory DME. Further randomized controlled studies are required to assess the effect of IFNα alone or in combination with other therapies for DME treatment.