title: Beta-adrenergic receptor antagonism in myopia.
abstract: A previous study has demonstrated that timolol maleate (0.5%), a non-selective beta-adrenergic antagonist, produces in emmetropes a significant reduction in accommodative convergence (AC) during the initial four minutes of a near-vision task. The present study has examined the effect of timolol on AC for three refractive groups (each comprising N = 20): emmetropes, early-onset myopes (EOMs), i.e. myopia onset prior to 15 years of age and late-onset myopes (LOMs), i.e. myopia onset after 15 years. A double-blind protocol was adopted between timolol and a saline control. AC was derived from accommodation stimuli of 3.3, 4.1 and 4.8 D with changes in heterophoria being assessed using a Maddox rod and tangent scale. The relationship between the ocular hypotensive effect of timolol and anterior corneal curvature was also investigated using a Goldmann applanation tonometer and a two-position keratometer (Haag-Streit). Timolol produced a significant reduction in AC in emmetropes but did not induce significant changes in AC in LOMs or EOMs. The timolol-induced reduction in IOP did not result in any changes in anterior corneal curvature.
mesh_terms: D000065:Accommodation, Ocular / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D003290:Convergence, Ocular / Q000187:drug effects; D003315:Cornea / Q000033:anatomy & histology / Q000187:drug effects; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009216:Myopia / Q000503:physiopathology*; D011932:Reading; D013997:Time Factors; D013999:Timolol / Q000494:pharmacology*
chemical_list: D000319:Adrenergic beta-Antagonists; D013999:Timolol