Sympathetic inhibition of accommodation after sustained nearwork in subjects with myopia and emmetropia


PURPOSE. The purposes of the present study were to assess the effect of a sympathetic inhibitory pharmacologic agent, timolol maleate, on the magnitude of nearwork-induced transient myopia (NITM) and its decay in different refractive groups for an extended near task duration and to determine the proportion of the young adult population manifesting effective sympathetic access under naturalistic closed-loop viewing conditions. METHODS. Ten subjects with emmetropia and 10 with myopia were tested. They read binocularly for 1 hour at a distance of 35 to 40 cm. NITM was calculated as the difference in distance refractive state after task as compared with before task immediately after reading. All subjects received timolol maleate to block the sympathetic nervous system and betaxolol as a control agent in independent test sessions separated by at least 3 days. Forty minutes after drug instillation, the NITM measurement procedure was repeated. RESULTS. Initial NITM magnitude was larger in subjects with myopia than in subjects with emmetropia before and after timolol instillation. Furthermore, NITM magnitude in subjects with sympathetic access was increased after timolol instillation. In contrast, with the control agent betaxolol, there was no increase. NITM decay duration to baseline was increased after timolol instillation in the subjects with myopia only. Only 15% of the subjects (n = 3 subjects with myopia) demonstrated effective and significant access to sympathetic facility. CONCLUSIONS. Subjects with myopia demonstrated an increase in decay duration with timolol, thus suggesting impaired sympathetic inhibition of accommodation. This may be a precursor for myopia progression in some persons.

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Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > School of Optometry > Optometry & Vision Science Research Group (OVSRG)
College of Health & Life Sciences
College of Health & Life Sciences > School of Optometry > Vision, Hearing and Language
Additional Information: Creative Commons Attribution Non-Commercial No Derivatives License
Uncontrolled Keywords: myopia,sympathetic nerves,accommodation,beta blockers,Medicine(all),Ophthalmology,Cellular and Molecular Neuroscience,Sensory Systems
Publication ISSN: 0146-0404
Last Modified: 03 May 2024 07:07
Date Deposited: 30 Nov 2009 11:34
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://www.iovs ... /iovs.08-1762v1 (Publisher URL)
PURE Output Type: Article
Published Date: 2009-01
Authors: Vasudevan, Balamurali
Ciuffreda, Kenneth J.
Gilmartin, Bernard

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