Comparison of Retinal Layer Thickness in Eyes with Resolved Diabetic Macular Edema Receiving Ranibizumab with Normal Eyes

Purpose: To evaluate the thickness of individual retinal layers in eyes with resolved diabetic macular edema (DME) after treatment with ranibizumab (RBZ). Methods: Spectral-domain optical coherence tomography (OCT) scans of 25 eyes (25 patients) with DME that had been treated with RBZ (and shown resolution of edema as evident by the absence of fluid in a high-resolution grid placed on the fovea) were acquired using Spectralis HRA + OCTTM. Thickness measurements of individual layers were calculated using papillomacular bundle (PMB), central subfield, and inner- and outer-ring Early Treatment Diabetic Retinopathy Study (ETDRS) grids. Measurements were compared to 45 normal eyes with no known retinal disease. A post-hoc analysis was done correlating visual acuity (VA) with individual retinal layer thickness. Results: Full retinal thickness (FRT) was thinner than normal individuals across all 4 grids. There were similarities and differences among the 4 grids; however, PMB and inner-ring ETDRS grids displayed the most resemblance. The VA significantly correlated with the FRT measured in PMB (p = 0.004), central subfield (p = 0.02), and inner-ring (p = 0.006) ETDRS. Conclusions: Segmentation of OCT scans revealed significant differences in the overall thickness of the retina and of individual retinal layers in patients with resolved DME. PMB grid showed a stronger correlation between affected retinal layers and VA compared to ETDRS. PMB also showed significance with VA in layers that were shown to be not significant in ETDRS grid.