PURPOSE The purpose of this study was to evaluate the impact of meibomian gland dysfunction (MGD) on the ocular surface of patients with medically treated glaucoma. MATERIALS AND METHODS This was a cross-sectional study in which 70 subjects with glaucoma on long-term (>1 year) topical hypotensive medications were recruited. MGD was defined as the presence of signs consistent with meibomian gland terminal duct obstruction. MGD was categorized between grades 1 and 4 and plus disease according to clinical severity. The ocular surface disease index (OSDI) questionnaire was completed at the time of enrollment. Ocular surface tests consisted of tear break-up time (BUT), ocular surface staining with lissamine green (LG), and Schirmer test with anesthesia. A Student t test, χ test, and Mann-Whitney U test were used in statistical comparisons. Forty-five healthy control subjects with no evidence of intraocular or ocular surface disease were also included. RESULTS MGD was detected in 56 (80.0%) subjects with glaucoma. Forty-seven patients (67.1%) had obstructive and 9 (12.9%) had atrophic type of MGD. Of these 56 cases, 47 (83.9%) had signs consistent with mild to moderate MGD. The ocular surface test results of patients with glaucoma with MGD and without MGD were significantly worse (P < 0.001) for all parameters compared with those of healthy controls. However, there were no significant differences between ocular surface disease index scores (P = 0.912), tear break-up time (P = 0.635), lissamine green scores (P = 0.248), and Schirmer results (P = 0.991) between patients with glaucoma with MGD and without MGD. CONCLUSIONS Mild to moderate MGD is frequently encountered in patients with medically treated glaucoma. However, the presence of MGD does not appear to have an additional detrimental effect on the ocular surface to that already induced by chronic topical medication use.