The investigators expect that when Cosopt is added the investigators will demonstrate improved IOP, morphology and blood flow compared to the latanoprost baseline. Furthermore the investigators expect the the diurnal fluctuation of IOP and choroidal blood flow will be stabilized on Cosopt therapy. The implications are that adding Cosopt to latanoprost can stabilize not only the IOP but also the damaging consequences of IOP to the optic nerve head.