Effect of Diabetic Macular Edema on Peripapillary Retinal Nerve Fiber Layer Thickness Profiles

PURPOSE. To investigate both the effect of diabetic macular edema (DME) on measured peripapillary retinal nerve fiber layer (RNFL) thickness and the effect of intravitreal bevacizumab injection on RNFL thickness using spectral-domain optical coherence tomography (SD-OCT) in patients with diabetic retinopathy. METHODS. We compared the SD-OCT RNFL thickness profiles between eyes with and without DME (DME [n = 42]; without DME [n = 53]) and conducted an interventional study for evaluating the effect of DME on RNFL thickness. Six sectorial and the global RNFL (gRNFL) thicknesses were compared between the two groups. To evaluate the intraindividual effect of DME on RNFL thickness, 1-month follow-up OCT data of 42 eyes that received an intravitreal bevacizumab injection were compared with preinjection data. RESULTS. The six sectorial and gRNFL thicknesses were greater in the DME group than the non-DME group (P < 0.05). The gRNFL thickness significantly correlated with the central foveal thickness (CFT) (R = 0.470, P < 0.001) and total macular volume (R = 0.786, P < 0.001). The 42 eyes that received intravitreal bevacizumab injections showed significant decreases of the CFT (P < 0.001) and gRNFL thickness (P < 0.001) after injection. Additionally, the changes in macular thickness and RNFL thickness were significantly correlated (R = 0.576, P < 0.001). CONCLUSIONS. The RNFL thickness was generally increased in patients with DME, and the increment correlated with the degree of macular edema. While long-lasting DME resulted in RNFL thickening in all sectors, short-term DME resolution mainly influenced the temporal and nasal RNFL thicknesses. Cautious interpretation is recommended for evaluation of glaucoma using RNFL thickness in diabetic patients, especially patients with DME.