Sympathetic innervation of ciliary muscle and oculomotor function in emmetropic and myopic young adults.
OBJECTIVE
Evidence exists for an additional inhibitory accommodative control system mediated by the sympathetic branch of the autonomic nervous system (ANS). This work aims to show the relative prevalence of sympathetic inhibition in young emmetropic and myopic adults, and to evaluate the effect of sympathetic facility on accommodative and oculomotor function.


METHODS
Profiling of ciliary muscle innervation was carried out in 58 young adult subjects (30 emmetropes, 14 early onset myopes, 14 late onset myopes) by examining post-task open-loop accommodation responses, recorded continuously by a modified open-view infrared optometer. Measurements of amplitude of accommodation, tonic accommodation, accommodative lag at near, AC/A ratio, and heterophoria at distance and near were made to establish a profile of oculomotor function.


RESULTS
Evidence of sympathetic inhibitory facility in ciliary smooth muscle was observed in 27% of emmetropes, 21% of early-onset myopes and 29% of late-onset myopes. Twenty-six percent of all subjects demonstrated access to sympathetic facility. Closed-loop oculomotor function did not differ significantly between subjects with sympathetic facility, and those with sympathetic deficit.


CONCLUSIONS
Emmetropic and myopic groups cannot be distinguished in terms of the relative proportions having access to sympathetic inhibition. Presence of sympathetic innervation does not have a significant effect on accommodative function under closed-loop viewing conditions.
Mallen
Edward A H
EA
Department of Optometry, University of Bradford, Richmond Road, Bradford, West Yorkshire BD7 1DP, UK. e.a.h.mallen@bradford.ac.uk
Gilmartin
Bernard
B
Wolffsohn
James S
JS
D000065:Accommodation, Ocular / Q000187:drug effects / Q000502:physiology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D015784:Betaxolol / Q000494:pharmacology; D002924:Ciliary Body / Q000503:physiopathology; D005133:Eye Movements / Q000187:drug effects / Q000502:physiology; D006801:Humans; D009130:Muscle, Smooth / Q000503:physiopathology; D009216:Myopia / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D009801:Oculomotor Muscles / Q000294:innervation* / Q000503:physiopathology; D012029:Refraction, Ocular / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013999:Timolol / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D013999:Timolol; D015784:Betaxolol