Macular oedema is a form of diabetic retinopathy that can be treated with photocoagulation. The expected effect of treatment varies, and may depend on the previous characteristics of retinal thickening. To determine whether the change in retinal thickness after focal photocoagulation for diabetic macular oedema varies due to the presence of anatomical features that may justify a separate assessment. Non-experimental, comparative, retrospective, longitudinal study. The mean percentage change in macular volume was compared in eyes with diabetic macular oedema, 3 weeks after focal photocoagulation. The analysis was stratified according to the presence of central and perifoveal temporal thickening (Mann-Whitney U). A regression analysis was performed to identify the contribution of the anatomical variables before photocoagulation to the change in macular volume. A total of 72 eyes were evaluated. The mean change of macular volume in the sample was -0.68±3.84%. In the multiple regression analysis, the changes of perifoveal temporal (beta 0.54, p<0.001) and central field thickness (beta 0.3, p =0.01) contributed to the change of macular volume (R=0.64). Macular volume decreased by a mean of -2.1±4.3% in eyes with temporal perifoveal thickening, and increased by 0.5±2.8% (p =0.007) in eyes with no thickening. Perifoveal temporal thickening before photocoagulation changes the expected effect of this therapy on macular volume in eyes with focal diabetic macular oedema. It is recommended to evaluate the effect separately, and according to the perifoveal temporal thickness. Copyright © 2015 Academia Mexicana de Cirugía A.C. Publicado por Masson Doyma México S.A. All rights reserved.