In this study, the investigators seek to better characterize the knowledge base of the intraocular pressure (IOP) lowering effects of pilocarpine in patients with open angle glaucoma or ocular hypertension who are currently taking latanoprost. The goal is to define the potential additive effect of pilocarpine throughout a 24-hour period, not only for IOP, but for ocular perfusion pressure (defined as 2/3[diastolicBP + 1/3(systolicBP - diastolicBP)] - IOP). These data will allow to expand current knowledge of the effects of pilocarpine and help determine if this medication has a useful role as an adjunctive treatment in glaucoma.