Background: Phacoemulsification (phaco) is one of the most widely used cataract surgery techniques nowadays. Various factors can influence the tissue structures of the eyeball eg. Ultrasonic energy, fluidics, mechanical effects, compression, and hypoxia on the tissue. Every step of this maneuver can cause direct or indirect effects on ocular tissues. Ultrasonic energy and fluidics produce mechanical effects that cause an inflammatory reaction which affects cornea, retina and choroid. Objective: To evaluate the effect of phacoemulsification on retina to compare these effects in diabetic and non-diabetic patient to reach a conclusion whether diabetic patient are more vulnerable to these effects or not. Patients and Methods: This is a prospective cohort observational study that included 100 eyes of 100 patients (50 diabetic patients (Type II), 50 non diabetic patients) having immature senile cataract. Patients were recruited from the ophthalmology department of Beni-Suef University. Results: In our study results  noted a statistically significant increase in the central macular thickness 1day, 1 week & 1 month postoperatively also there was no statistically significant difference in the central macular thickness between the Diabetic and Non-diabetic group neither pre-operatively, nor post-operatively. Conclusion: Phacoemulsification affects the macula, phaco power used during the surgery and inflammatory mediators released after the surgery leads to long term increase in Central macular thickness in both diabetic and non-diabetic patients. It was noticed that phacoemulsification causes increase in Central macular thickness noticed at one week & one month post-operatively in both diabetic and non-diabetic patients.  Finally we can say that cataract phacoemulsification cause t increase in central macular thickness.