The proposed crossover study will compare for the first time the quality of 24-hour intraocular pressure control with the combination of travoprost and brinzolamide/timolol compared with travoprost and brimonidine/timolol in glaucoma patients insufficiently controlled with travoprost. This comparison may determine the real efficacy of the two fixed combinations when added to the prostaglandin. The design of the proposed study should facilitate a better understanding of the role of these medications in glaucoma management.