The Effect of a β -Adrenoceptor Antagonist on Accommodative Adaptation in Hong Kong Children

Abstract

Purpose: Increased susceptibility to nearwork-induced accommodative adaptation has been suggested as a risk factor for myopia development. We investigated whether accommodative adaptation may explain in part the high prevalence of myopia in Hong Kong children and examined the effect of β -antagonism with topical timolol maleate on accommodative adaptation.Methods: Thirty children (10 emmetropes and 20 myopes) aged between 8 and 12 years were recruited. Tonic accommodation was measured before and after 5 min of video game–playing using an open-field Shin-Nippon autorefractor. Measurements were repeated 30 min after timolol instillation.Results: Children with progressing myopia demonstrated accommodative adaptation following the near task, whereas stable myopes showed counter-adaptive, hyperopic accommodative changes. Timolol increased the magnitude of accommodative adaptation in the stable myopes but had little effect on responses of the progressing myopes or emmetropes.Conclusions: Neuropharmacological modulation of the accommodative system may have a possible etiological role in the progression of myopia.

KEYWORDS:

• accommodation
• children
• myopia
• nearwork
• sympathetic innervation