Comparison of Optical Coherence Tomography Biomarkers between Bevacizumab Good Responders and Nonresponders Who were Switched to Dexamethasone Implant in Diabetic Macular Edema

PURPOSE: To compare volumetric optical coherence tomography (OCT) biomarkers in bevacizumab responsive and bevacizumab refractory diabetic macular edema (DME) patients switched to the dexamethasone implant to ultimately identify possible prognostic indicators. METHODS: Retrospective analysis of DME patients treated with bevacizumab were done. Patients were divided into those who showed response to bevacizumab (bevacizumab only group) and others who were switched to the dexamethasone implant due to lack of response to bevacizumab (switching group). Volumetric OCT biomarkers such as central macular thickness (CMT), inner and outer cystoid macular edema (CME) volume, serous retinal detachment (SRD) volume, retinal volume (CME + SRD volume) within the 6-mm Early Treatment of Diabetic Retinopathy Study circle were calculated. OCT biomarkers were followed up throughout treatment. RESULTS: Among total of 144 eyes, 113 patients were included in the bevacizumab only group and 31 patients were included in the switching group. Compared to the bevacizumab only group, the switching group showed higher baseline CMT (558.00 ± 209.60 μm vs. 454.96 ± 125.88 μm, p = 0.003), larger inner CME (6.02 ± 1.43 mm(3) vs. 5.12 ± 0.87 mm(3), p = 0.004) and SRD volume (0.32 ± 0.40 mm(3) vs. 0.11 ± 0.09 mm(3), p = 0.015) and higher proportion of patients with SRD (58.06% vs. 31.86%, p = 0.008). In the switching group, CMT, inner CME and SRD volume all showed significant reduction after switching to the dexamethasone implant. CONCLUSIONS: DME with large SRD and inner nuclear layer edema volume may be more effectively treated with the dexamethasone implant than bevacizumab.