Purpose: To evaluate the macular thickness changes in diabetic macular edema after meal. Methods: In this prospective case series, macular thicknesses of diabetic patients with clinically significant macular edema (CSME) were measured after 7 h of fasting and repeated 2 h after breakfast. Results: Thirty six eyes of 20 diabetic patients were evaluated. The mean central subfield thickness (CST) and maximum retinal thickness (MRT) significantly decreased after meal (mean change of -10.3 +/- 14.3 mu m and -13.1 +/- 12.7 mu m, respectively, both P < 0.001). A decrease in CST and MRT values was found in 23 (63.8%) and 28 (77.7%) eyes, respectively, and no eye had an increase in retinal thickness measurements. Significant correlation was found between CST and MRT change and fasting thickness measurements (P = 0.001 and P = 0.01, respectively) and intraretinal cystic spaces (P = 0.001 and P = 0.03, respectively). Mean MRT change was significantly higher in the presence of subretinal fluid (P = 0.01). Conclusion: Retinal thickness measurements may change after meal. So, fasting state of diabetic patient should be considered in measurement of macular thickness of patients with CSME. Copyright (C) 2015, Iranian Society of Ophthalmology. Production and hosting by Elsevier B.V.