The present invention provides a method for identifying a compound having muscarinic agonist activity that will lower intraocular pressure without causing miosis which comprises measuring the activity of the compound at the m.sub.3 and m.sub.5 muscarinic receptors and determining from the activity measurement a compound having at least twice the agonist activity at the m.sub.5 receptor as compared to the m.sub.3 receptor. Preferably, the method of measuring said muscarinic agonist activity comprises eliciting phosphoinositide hydrolysis in CHO-K1 cells stably expressing the m.sub.3 and m.sub.5 muscarinic receptor subtypes. The present invention also provides a method of lowering the intraocular pressure in a mammal which comprises administering to said mammal a compound that has been determined to have at least twice the agonist activity at the m.sub.5 receptor as compared to the m.sub.3 receptor.