Background: In recent years, there has seen great progress in cataract surgery, both in the surgical technique as well as with modern phacoemulsifiers. Optical Coherence Tomography (OCT) is a noninvasive and noncontact diagnostic tool with high resolution to assess macular changes. Purpose: To assess the impact of uncomplicated phacoemulsification on the changes of central macular thickness (CMT) values in diabetic and non-diabetic patients. Methods: Thirty eyes of 30 subjects who underwent uneventful phacoemulsification were divided into 3 equal groups: Group I: Non diabetic patients, Group II: Diabetic patients without retinal changes and Group III: Diabetic patients with mild to moderate non-proliferative diabetic retinopathy (NPDR). Each patient was subjected to routine examination, best corrected visual acuity and CMT was assessed by OCT one day before operation, one week, one month and six months after the operation. Results: According to CMT, significant difference was reported after one month and six months between all groups. This study showed statistically significant differences between groups one week, one month and six months postoperatively according to BCVA. Also there were statistically significant differences over the periods through BCVA in the each group, negative significant correlations between CME and BCVA after 1 month and 6 months. The mean BCVA improved progressively in the postoperative period, and it was non-significant correlated with duration of DM one week postoperatively. However, the correlations were significant after one month and six months. The CMT increased progressively in the postoperative periods and it significantly correlated with the duration of DM after one month and six months. Conclusion: Diabetes influenced the central macular thickness in diabetic patients, who were more liable to changes in central macular thickness after cataract surgery even with uncomplicated cataract surgery.