Background: Cataract is the chief cause of avoidable blindness in Pakistan and throughout the world. Cataract surgery can be performed more easily and safely if mydriasis can bemaintained until intraocular lens implantation and for better visualization of the posterior chamber. Which facilitate proper incision of the anterior capsule, safe removal of the cataract, and implantation of intraocular lens. The main options for eye drops are ketorolac tromethamine, diclofenac, flurbiprofen, indomethacin and nepafenac. Nepafenac, a latest NSAID, also showed good results. It is dissolved in the tissues to Amfenac, a potent inhibitor of cyclooxygenase-1 (COX-1) and COX-2 enzymes. Objective: To determine the efficacy of preoperative use of nepafenac in maintenance of intra-operative mydriasis during cataract surgery. It was a descriptive case series study, was carried out at Department of Ophthalmology Unit I, Dow University of Health Sciences and Civil Hospital Karachi, from 10th January, 2019 to 9th July, 2019. Material & Methods. All patients who fulfilled the inclusion criteria and visited Department of Ophthalmology were included in the study. Nepafenac eye drops installed three times at half hour interval preoperatively. Pupil size was measured with a sterilized caliper at the start of surgery, after removal of lens and after implantation of intraocular lens during surgery. All the collected data were entered into the performa attached at the end. It was recorded on performa and used electronically for research purpose. Results: Mean ± SD of age was 62.45±8.42 with C.I (61.24-63.65) years. Mean ± SD of pupil size was 8.33±1.94 with C.I (8.05--8.60) mm. Out of 190 patients 112 (58.94%) were male while 78(41.06%) were female. Efficacy of nepafenac was found in 162(85.26%) patients while 28 (14.74%) patients was found to be non-effective. Conclusion. It is to be concluded that the efficacy of preoperative use of Nepafenac in maintenance of intra-operative mydriasis during cataract surgery was found to be effective in preventing meiosis during cataract surgery. [ABSTRACT FROM AUTHOR]