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Beta-adrenergic receptor antagonism in myopia.
1Department of Vision Sciences, Aston University, Birmingham, U.K.
Summary
Timolol maleate significantly reduced accommodative convergence (AC) in emmetropes but not in myopes. This non-selective beta-adrenergic antagonist did not alter intraocular pressure-related corneal curvature.
Area of Science:
- Ophthalmology
- Optometry
- Pharmacology
Background:
- Timolol maleate, a beta-blocker, previously showed reduced accommodative convergence (AC) in emmetropes.
- The effect of timolol on AC in different myopia groups remained unexamined.
Purpose of the Study:
- To investigate the impact of timolol maleate on accommodative convergence in emmetropes, early-onset myopes (EOMs), and late-onset myopes (LOMs).
- To assess the relationship between timolol's ocular hypotensive effect and anterior corneal curvature.
Main Methods:
- A double-blind, placebo-controlled study involving 60 participants (20 emmetropes, 20 EOMs, 20 LOMs).
- Administration of 0.5% timolol maleate or saline control.
- Measurement of accommodative convergence using varying diopter stimuli and assessment of heterophoria with Maddox rod and tangent scale.
- Evaluation of anterior corneal curvature and intraocular pressure (IOP) using Goldmann applanation tonometer and keratometer.
Main Results:
- Timolol maleate significantly reduced AC in emmetropes.
- No significant changes in AC were observed in either EOMs or LOMs.
- Timolol-induced reduction in IOP did not affect anterior corneal curvature.
Conclusions:
- Timolol maleate's effect on accommodative convergence is refractive-error dependent, significantly impacting emmetropes but not myopes.
- Timolol does not alter corneal curvature, suggesting its effects on AC are not mediated by changes in corneal biomechanics.