Background: A cataract is a opacity in the normally transparent crystalline lens of the eye. This opacity can cause a decrease in vision and may lead to eventual blindness. The prevalence of cataract increases with often occurs earlier in life, and there is more of it. Globally, cataract has remained the major cause of blindness over the years. Cataract is one of the most common causes of visual impairment in the world. In India 80% of the blindness is due to cataract, Various modifiable risk factors associated with cataract include UV exposure, diabetes, hypertension, body mass index (BMI), drug usage, smoking and socioeconomic factors; but advancing age is the single most important risk factor for cataract. Objectives: To assess the pre- test and post- test level of knowledge and practice regarding prevention of postoperative complications among patients undergoing cataract surgery To determine the effectiveness of pre-operative teaching program me on knowledge and practice regarding prevention of postoperative complications among patients undergoing cataract surgery To correlate the pre and post test level of knowledge and practice regarding prevention of postoperative complications among patients undergoing cataract surgery To associate the post test level of knowledge and practice with their demographic variables among patients undergoing cataract surgery Method: Research approach was quantitative approach, The research design was adopted quasi experimental two group pre test post test Design, The sample size was 100 patients undergoing cataract surgery were selected by using Non probability purposive sampling technique at SRM GH, Kattankulathur, patients were divided in to two groups, such as 50 samples in experimental group and 50 samples in control group ,Pre test was conducted for experimental and control group , on day of before surgery to assess the level of knowledge by using structured questionnaire, level of practice assessed by observational checklist , pre operative teaching on prevention of post operative complications and booklet was given only to experimental group , after 2 weeks post test was conducted for both experimental and control group. After completion of the study booklet on prevention of postoperative complications was given to the control group. The data was collected from the sample were tabulated and analysed and interpreted using both descriptive and inferential statistical method. Result: In experimental group pre-test p value 0.378 is not less than 0.05 and is not significant, post test p value 0.007 is less than 0.01 and is highly significant at 1% level hence we can say that there is high significant positive correlation ( r=0.378 ) between level knowledge and practice scores regarding prevention of postoperative complications, It means that, both knowledge and practice are interdependent and if knowledge is increasing then the practice is also increasing simultaneously. In control group pre test p value 0.117 is not less than 0.05 and is not significant ,post test p value 0.998 is not less than 0.05 and is not significant at 5% level hence we can say that there is no significant correlation between level of knowledge and practice scores regarding prevention of postoperative complications. Conclusion: The result of the study was concluded, Preoperative teaching formulated by the investigator was effective in improving the knowledge and practice of patients undergoing cataract surgery regarding prevention of Postoperative complications.