The aim of the study was to determine the effects of a dopaminergic drug, 2% ibopamine, on the pupil, intraocular pressure and other ocular and ultrasound biometric variables. Thirty healthy subjects and 15 patients with primary open-angle glaucoma, aged from 40 to 78 years (mean age: 59.2 +/- 11), were included in two prospective open controlled trials. In the first, the mydriatic effect of 2% ibopamine and its inhibition and reversibility were evaluated in 15 healthy subjects using the alpha1-adrenergic drug, 0.5% dapiprazole. In the second, refraction, visual acuity, pupil diameter, intraocular pressure and 5 A-scan ultrasound biometric variables were evaluated in 15 healthy subjects and in 15 glaucoma patients. As early as forty min after administration of 2% ibopamine, a marked mydriatic effect (7.3 vs 3.9 mm; P < 0.0001), which was completely inhibited or reversed by 0.5% dapiprazole, was detected. The drug induced no changes in refraction, visual acuity or A-scan ultrasound biometric variables in any of the subjects examined. In healthy subjects, the intraocular pressure values were not changed to a statistically significant extent (13.8 vs 14.8 mm Hg; P = 0.668), whereas a slight, though significant, hypertensive effect (24 vs 22.2 mm Hg; P = 0.002) was observed in the glaucoma patients. The study confirms the intense mydriatic effect of 2% ibopamine with no changes in refraction, visual acuity or A-scan ultrasound biometric variables. The drug has no effect on intraocular pressure in healthy subjects, but induces a significant hypertensive effect in patients with initial glaucoma. This characteristic could be used for early diagnosis of primary open-angle glaucoma.