Purpose: This study was aimed to measure the impact of self-efficacy theory to improve medication adherence among older adults’ patients with glaucoma. Methodology: A quasi-experimental design was used to investigate the study hypotheses.  Study Sample: A total of 284 older adults with glaucoma were screened to select non-adherent patients with medication. The recruited study sample was (152) who are non-adherent with glaucoma medication divided equally into (76 study group) and (76 control group). Setting: the study was conducted at the outpatient clinics of Ophthalmology at University Hospital, Shebin El-Kom, Egypt.  Tools: three tools were used for the purpose of data collection (I) Bio-socio-demographic characteristics questionnaire; (II) Medication Adherence Rating Scale (III) Glaucoma Medication Self-Efficacy Scale. Findings: The findings revealed that the mean age of the studied sample was 74.86+4.63 (non-adherent to medication). Patients age and presence of more than three multiple chronic illnesses with poly-medications are the highest risk factors of adherence to medications (OR = 10.9; 95% CI 6.8 -16.32, P = 0.000); (OR = 12.6; 95% CI 8.2 -18.4, P = 0.000) and (OR = 13.2; 95% CI 7.4 -19.8, P = 0.000) respectively. Participants who received the intervention program showed a significant improvement in their self-efficacy in overcoming medication adherence barriers compared to the control group. An improvement of the self-efficacy in their ability in carrying out glaucoma medication correctly compared to the control group was shown by highly statistically significant differences between total mean scores at (t =3.426, P =.001; t =17.174, P=.000; t =18.141, P=.000) respectively. The intervention program of glaucoma medication management had a positive impact on the patients’ outcomes compared to the control group. There is a statistically significant difference between patients’ feelings and thoughts pre and post-intervention was detected. Unique contribution to theory, practice and policy: The findings confirm the effectiveness of an intervention/educational program based on self-efficacy theory in terms of improving glaucoma medication adherence among older adults. Glaucoma’s medication principles should be discussed at regular intervals based on patients' needs and the barriers they are facing.