Biological Activity of Ranibizumab in Diabetic Macular Edema: A Prospective Study Evaluating Retinal Structure and Function

Purpose: Recent pilot clinical studies have suggested that ranibizumab (Lucentis), a humanized antigen-binding antibody fragment targeting all Vascular Endothelial Growth Factor(VEGF)-A isoform and their biologically active degradation products, may be effective in improving vision and reducing central retinal thickness in patients with diabetic macular edema (DME). The aim of this study was to evaluate prospectively macular structure and function in DME patients undergoing repeated intravitreal injections of Lucentis. Methods: Sixteen diabetic patients (age range 25-56 years) were enrolled in the study. Their baseline visual acuity ranged 1-0.84 logMAR, macular thickness (OCT3) 310-640 microns, and central microperimetric (Nikon MP-1) sensitivity 2 to 10 dB. Each patient underwent weekly assessment, for three months, of visual acuity, microperimetry and focal electroretinogram (FERG), performed according to a published technique. Results: Following the first intravitreal injection, mean visual acuity, microperimetric sensitivity and FERG amplitude increased steadily from baseline values over the treatment period, with further improvements following each intravitreal injection. In parallel with functional changes, mean central retinal thickness decreased exponentially from baseline, with a marked reduction over the first month of treatment, and further improvement (although smaller) over the second and third months. Conclusions: The results confirm improvement of retinal structure and function following Lucentis injection in diabetic macular edema, and suggest an additivity of the drug effect when repeatedly administered over the first three months of treatment.