Ocular effects of selective alpha-adrenergic agents: a new drug paradox?

Alpha-adrenergic drugs can alter pupil size as well as intraocular pressure (IOP) when administered topically to the eye. Recent experiments using the more selective alpha-adrenergic agents suggest that these responses may be mediated by at least three subtypes of alpha-adrenergic receptors. These studies have also given rise to an apparent paradox because both agonists and antagonists cause a lowering in IOP.