Objective: To investigate the effects of type 2 diabetes mellitus on visual field defect, retinal nerve fiber layer thickness and intraocular pressure index in patients with primary open angle glaucoma. Methods: A total of 125 patients (125 eyes) diagnosed with primary open-angle glaucoma in our hospital from April 2016 to September 2017 were enrolled as the research subjects. Patients were divided into case group (70 cases) and control group (55 cases). Patients in case group were diabetic patients combined with primary open-angle glaucoma, while the control group consisted of patients only with primary open-angle glaucoma. Mean defect of visual field, mean light sensitivity in visual field, retinal nerve fiber layer thickness and intraocular pressure index were compared between two groups. Results: Mean defect of visual field in case group was (17.26 ± 3.15 dB), which was significantly higher than that in the control group (P<0.05). Mean light sensitivity in case group was (14.98 ± 4.27 dB), which was significantly lower than that in control group (P<0.05). Compared with control group, thickness of retinal nerve fiber layer at superior and inferior quadrants was lower than that in case group (P<0.05). There was no significant difference between the two groups in thickness of temporal, nasal and peripheral quadrant (P>0.05). Intraocular pressure of case group was (22.75 ± 2.61 mmHg), which was significantly higher than that of control group (P<0.05). Conclusion: Type 2 diabetes can increase defect area of visual field, increase intraocular pressure, reduce retinal nerve fiber layer thickness and promote the progression of the disease in patients with primary open angle glaucoma. © 2017, Scientific Publishers of India. All rights reserved.