Retinal layers thickness changes in diabetic macular edema treated by bevacizumab and its relationship with visual outcome

Purpose: To evaluate the effect of intravitreal bevacizumab (IVB) on thickness changes of individual retinal layers in diabetic macular edema (DME) as well as to identify the relationship of thickness changes and final visual acuity Methods: In a prospective interventional case series 29 eyes from 29 patients with center involved DME were included, according to spectral domain optical coherent tomography (SD-OCT) and visual acuity criteria. IVB was injected at base, weeks 4 and 8, after that was injected until week 24 based on as needed protocol. The manual segmentation of different retinal layers were performed on SD-OCT scans at base and week 24. Thickness changes of retinal layers were determined and correlated with final visual acuity Results: The mean of best corrected visual acuity (BCVA) was improved from 61 to 69 ETDRS letters at final visit. (P<0.001) Furthermore, the mean of central macular thickness (CMT) was decreased significantly from 409 to 315 microns. (P<0.001) In central subfield, the thickness of retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), and outer nuclear layer were decreased significantly at last follow up (P<0.05 for all). Multivariate regression analysis showed that final BCVA was significantly correlated with baseline visual acuity and thickness decrease of the RNFL, IPL and ONL. However, the patients with less baseline visual acuity showed more improvement in vision, (r=0.776, P<0.001) but the patients with better baseline visual acuity had better final acuity. (P=0.012)Conclusion: In patients with DME who received IVB, the final visual acuity is significantly correlated with baseline visual acuity and thickness decrease of RNFL, IPL and ONL