Most studies found a lower incidence of systemic and ocular adverse events with fixed combinations than with the unfixed combinations. Fixed combinations are better tolerated than their respective prostaglandin analogue. However, among the most serious side effects induced by PGA are the breaking down of the blood-aqueous barrier (BAB) and the development of cystoids macular edema (CME). Also, timolol maleate drops increase protein concentration in the human and benzalkonium chloride, eye drops preservative induces anterior chamber inflammation. This randomized, masked-observer, prospective clinical trial was approved by the Ethics Committee of the University of Campinas, and it adhered to the tenets of the Declaration Of Helsinki. Written informed consent was obtained from each patient.