Background: Nowadays, intraocular surgery is widely performed and the ophthalmic nurse is the backbone of the eye care. Any deficiency in providing adequate nursing care pre or post eye surgery can lead to serious complications. The study aimed to: Evaluate the effect of implementing the nursing guideline on nurses' performance regarding patients undergoing cataract or glaucoma surgery. Method: Quasi-experimental research design was utilized to conduct this study. Sample: A convenience sample of 36 nurses working at Ophthalmology Mansoura Hospital was included in this study. Tools: Data were collected using two tools, first tool was pre/post structured questionnaire sheet, and it included two parts; part 1- included socio demographic characteristics of the studied nurses and part 2- included nurses' knowledge regarding the care provided to patients with cataract or glaucoma surgery. Second tool was pre/post observation checklist for nurses' practice pre, and post surgery. Results: Post implementing the guideline; there were high statistical significant differences in nurses’ knowledge, preoperative practice, and postoperative practice (p<0.001) and a statistical significant relation was found between nurses' educational level with their knowledge, preoperative practice, and postoperative practice (p=0.044, 0.050, 0.048 respectively). Conclusion: Applying the designed nursing guideline is effective in improving nurses' knowledge, and practice regarding the care provided to patients with cataract or glaucoma surgery. Recommendation: It is recommended to; develop a specialized orientation program for the newly appointed nurses, provide the nurses with continuous training courses, set restrict supervision on nurses' application for infection control precautions, and encourage them to become involved in research studies.