The macular function and structure in patients with diabetic macular edema before and after ranibizumab treatment

Purpose To evaluate macular function and structure in patients with diabetic macular edema prior to, as well as 3 and 6 months after intravitreal ranibizumab treatment. Patients and methods Seventeen eyes of 17 patients with type 2 diabetes mellitus and diabetic macular edema (DME) were treated with intravitreal injections of 0.5 mg ranibizumab. Prior to the first injection, as well as after 3 and 6 months, the following examinations were performed: assessment of distance best-corrected visual acuity (log MAR), perception of metamorphopsia (M-Chart), slit lamp examination of the anterior and posterior segment of the eye (Volk 90D lens), evaluation of the retinal and choroidal circulation (fluorescein angiography), assessment of the structure and thickness of the macula (OCT), as well as evaluation of the macular function (PERG and mfERG). Results We observed that ranibizumab significantly improved visual acuity after 3 and 6 months from the beginning of the treatment, which was a consequence of reduced macular edema and vascular leakage. There was a statistically significant decrease in metamorphopsia frequency at month 3; however, at month 6 it was a statistically insignificant when compared to the baseline. The results of electrophysiological examinations revealed no improvement in ranibizumab-treated patients. Conclusion Improvement of visual acuity and reduction in macular thickness were maintained up to the 6-month follow-up. The results of electrophysiological examinations revealed that ranibizumab injections tend to stabilize bioelectrical macular function of the outer, middle and inner retinal layers, which was impossible to recognize on the basis of visual acuity and OCT. Therefore, the electrophysiological examinations should be used as an additional objective tool for the evaluation of the anti-VEGF treatment effectiveness in DME.