Multifocal ERG Changes as an Indicator for Short-Term Outcome after Intravitreal Injection of Ranibizumab in Treatment of Diabetic Macular Oedema

Abstract

Background: compared to laser photocoagulation, intra vitreal injection of anti-vascular endothelial growth factors (Anti VEGFs) have more desirable results and fewer complications. Study of this issue by multifocal electroretinogram (mf-ERG) revealed significant improvement in macular function associated with decreased retinal thickness using optical coherence tomography (OCT) and improvement of best corrected visual acuity (BCVA). Purpose: To study the role of multifocal Electroretinogram in the follow up of diabetic macular edema after intravitreal injection Ranibizumab and study its correlation to visual acuity and optical coherence tomography changes. Methods: A non-randomized prospective study was carried out from February 2018 to August 2018 on 32 eyes of patients with diffuse or focal DME without macular ischemia. The patients were selected from the outpatient ophthalmology clinic of Al-Hussein University hospital. The patients were injected intravitreally by Ranibizumab 0.5mg/0.05mL at baseline, 1 and 3 months. In this study we assessed pre and post-injection BCVA, IOP measurement by applanation tonometer, OCT and multifocal ERG changes over 3 months. Results: log MAR BCVA improved from (0.88±0.12) preoperatively to (0.53±0.18) at the end of the 3rd month, with P-value <0.001. Central subfield thickness 1 mm improved from (408.73±79.40µm) preoperatively to (224.33±32.49µm) at the end of the 3rd month, while para and peri-foveal thickness improved from (402±46.52µm) preoperatively to (286.30±32.67µm) at the end of the 3rd month, with P-value <0.001. P1 amplitude in ring 1 using MF-ERG improved from (33.08±10.59 nv/deg2) preoperatively to (58.30±32.67 nv/deg2) at the end of the 3rd month, with P-value<0.001. P1 amplitude in ring 2 using MFERG improved from (18.82±5.01 nv/deg2) preoperatively to (26.36±3.006 nv/deg2) at the end of the 3rd month, with P-value in the 1st month <0.05, while in the 3rd month <0.001. P1 implicit time in ring 1 using MF-ERG improved from (78.65±12.37 ms) preoperatively to (63.78±15.73 ms) at the end of the 3rd month, with P-value in the 1st month <0.05, while in the 3rd month <0.001. P1 implicit time in ring 2 using MF-ERG improved from (48.81±6.44 ms) to (44.39±4.06 ms) at the end of the 3rd month, with P-value in the 1st and 3rd months <0.05. Complications during follow up of patients especially 1week after injection were relatively uncommon, including mild subconjunctival haemorrhage in 1 eye (3.3%) and transient increase of IOP in 4 eyes (13.33%). Conclusion: Intravitreal injection of Ranibizumab resulted in improvement of macular function in study patients with diabetic macular edema. Postoperative improvement in visual acuity was accompanied by decreased retinal thickness measured by OCT and improvement of P1 amplitude in the central ring measured by MF-ERG.