The aim of the study was to assess a relationship between circulating platelet aggregates (CPA) and progression of visual field loss in primary open-angle glaucoma patients. CPA was determined in 27 patients with open-angle glaucoma with nonprogressive visual field loss and 15 patients with open-angle glaucoma and progression of visual field loss. Intraocular pressure (IOP) under topical therapy was < 18 mmHg in all patients. CPA in glaucoma patients with progression of visual field loss was not significantly higher than those without visual field progression (p = 0.59). In conclusion, our study shows that increased platelet aggregability is not solely responsible for progression of visual field loss in glaucoma patients, and indicates the role of IOP in the pathogenesis of visual field loss.