Cataract surgery is known to elicit postoperative macular oedema. Although the exact pathomechanism is not known, the role of surgical trauma and release of prostaglandin is suspected. The aim of the study was to measure the mean foveal thickness MFT after uneventful phacoemulsification and posterior chamber intraocular lens (PC IOL) implantation using Optical coherence tomography (OCT). OCT is a fundamentally new type of medical diagnostic imaging modality.Our study included 50 eyes of 48 patients divided into 2 groups; Group 1 (Diabetes mellitus group) consisted of 25 eyes (25 diabetic patients) and Group 2 (Control group) consisted of 25 eyes (23 non-diabetic patients). All patients were admitted for Phacoemulsification and PC IOL implantation. MFT was evaluated preoperative and 7, 30, and 60 postoperative. There is no correlation between MFT and age, but there is a highly significant correlation between MFT and staging of diabetic retinopathy , duration of DM. Statistically significant moderate correlation was detected between BCVA and MFT after one and two months postoperative.