 Cosopt dorzolamide hydrochloride-timolol maleate ophthalmic solution is combination of a topical carbonic anhydrase inhibitor and a topical beta-adrenergic receptor blocking agent. Each of these two components reduces intraocular pressure. The IOP-reducing effect of Cosopt b.i.d. was greater 1-3 mm Hg than that of monotherapy with either 2.0 dorzolamide t.i.d. or 0.5 timolol b.i.d. The IOP-lowering effect of Cosopt b.i.d. was approximately 1 mm Hg less than that of concomitant therapy with 2.0 dorzolamide t.i.d. and 0.5 timolol b.i.d. A previous study showed that the retinal circulation AVP time was significantly accelerated after replacing Timoptic with Cosopt in glaucoma patients Harris, 1999. 