OBJECTIVE To determine the prevalence of open-angle glaucoma (OAG), glaucoma suspects (GS), and ocular hypertension (OHT) in patients with thyroid-related immune orbitopathy (TRIO) and compare it with a control group. METHODS In this cross-sectional analytic study, 233 eyes of 117 patients with TRIO (case group) and 240 eyes of 120 normal age and sex-matched individuals (control group) underwent complete ocular examinations. Grave orbitopathy (GO) was diagnosed by clinical examinations with the help of an endocrinologist and para clinic tests. Controls were selected among apparently healthy individuals with no history of previous orbitopathy or thyroid diseases. RESULTS Prevalence of OAG and OHT was 2.5% and 8.5% in the case group, respectively. In contrast, OAG was detected in only 2 eyes (0.8%) of the control group and there were no instances of GS or OHT in the control group. Although the prevalence of OAG and GS were higher in cases than controls, this difference was not statistically significant. However, OHT was more common in cases (P<0.01). Ten eyes in the case group (4.3%) developed compressive optic neuropathy (CON); high intraocular pressure was detected in 5 of them (2.1%). All cases of OAG and GS in the case group were classified as stage 3 or higher of No symptoms or signs, Only signs no symptoms, Soft tissue, Proptosis, Extraocular muscle, Cornea, Sight loss. Active GO was only more prevalent in patients with OHT (P<0.001). CONCLUSIONS The prevalence of OHT was higher in cases with GO than age and sex-matched controls. Ophthalmologic examinations including intraocular pressure measurement (and if needed automated visual fields) should be regularly performed in patients with GO particularly in higher stages and those with active disease.