AIM: To evaluate the long-term response to the fixed combination of dorzolamide/timolol in patients with primary open angle glaucoma (POAG) and the addition of other intraocular pressure (IOP) lowering medications such as prostaglandin analogs and brimonidine.METHODS: A retrospective, non-randomized, and descriptive clinical study was performed with 182 eyes diagnosed with POAG. Patients were divided into three groups:a group with fixed combination of dorzolamide/timolol only, a second group with prostaglandin analogs plus fixed combination of dorzolamide/timolol, and a third group with the addition of brimonidine to the same fixed combination. IOP data were gathered retrospectively and the differences between groups were calculated.RESULTS: IOP was reduced satisfactorily in all three groups; however, a progressive IOP reduction was noted in the group with the fixed combination plus prostaglandin analogs. In this group, a progressive, significant and more homogeneous response of the reduction was noted in comparison with the other groups.CONCLUSION: IOP reduction was efficacious in all three groups. The addition of prostaglandin analogs showed progressive IOP reduction, progressive response and absence of long-term drift. Brimonidine did not show a significant additive effect.