Background: Diabetic retinopathy DR is a complication of DM that affects the blood vessels of the retina and leads to blindness. To control or prevent vision loss, appropriate health education is necessary to encourage those at risk to seek timely and appropriate care.  Purpose: To evaluate the effectiveness of an educational program in improving the knowledge of patients having diabetic retinopathy.  Design: Quasi-experimental research design was utilized in this study. Sampling; A purposive sample of 80 critically ill patients divided equally into study and control groups. Setting: Ophthalmology Damietta Hospital emergency. Instruments:  Knowledge of patients about diabetic retinopathy structured interview questionnaire was used80% of patients in the study group had good knowledge in comparison with 38% of patients in the control group. 76% of study group patients had good knowledge compared to only 38% of patients in the control group Conclusion: Applying the educational program was effective in improving patients' knowledge. Recommendation: Health care providers involving ophthalmic nurses should receive health education about diabetic retinopathy.