AIM:To present the outcome of modified grid laser photocoagulation (GLP) in diffuse diabetic macular edema (DDME) in eyes without extrafoveal and/or vitreofoveal traction. METHODS:Inclusion criteria for the retrospective study were DDME eyes of patients with type II diabetes mellitus that had ≥4 months of follow-up following GLP. Only one eye per patient was analyzed. Using 3-D spectral-domain optical coherence tomography (3-D SD-OCT), eyes that had either extrafoveal or vitreofoveal traction, or had been previously treated by an intravitreal medication(s) were excluded. Treated DDME eyes were divided into 4 groups:A) “Classic” DDME that involved the central macula; B) edema did not involve the macular center; C) eyes associated with central epiretinal membrane (ERM); D) DDME that was associated with macular capillary dropout ≥2 disc-diameter (DD). RESULTS:GLP outcome in 35 DDME eyes after 4-24 (mean, 13.1±6.9) months was as follows:Group A) 18 eyes with “classic” DDME. Following one or 2 (mean, 1.2) GLP treatments, best-corrected visual acuity (BCVA) improved by 1-2 Snellen lines in 44.4% (8/18) of eyes, and worsened by 1 line in 11.1% (2/18). Central macular thickness (CMT) improved by 7%-49% (mean, 26.6%) in 77.8% (14/18) of eyes. Causes of CMT worsening (n=4) were commonly explainable, predominantly (n=3) associated with emergence of extrafoveal traction, 5-9 months post-GLP. Group B) GLP(s) in DDME that did not involve the macular center (n=6) resulted in improved BCVA by 1-2 lines in 2 eyes. However, the central macula became involved in the edema process after the GLP in 3 (50%) eyes, associated with an emergence of extrafoveal traction in one of these eyes 4 months following the GLP. Group C) GLP failed in all 5 eyes associated with central ERM. Group D) GLP was of partial benefit in 2 of 6 treated eyes with macular capillary dropout ≥2DD. CONCLUSION:Eyes with DDME that involved the macular center were found to achieve favourable outcomes after GLP(s) during mid-term follow-up, unless complicated pre-GLP or post-GLP by vitreoretinal interface abnormalities, often extrafoveal traction or ERM, or by capillary dropout ≥2DD. Prospective studies with larger cohorts are required.