The accommodative response, refractive error and mental effort: 1. The sympathetic nervous system.
The accommodative response of 12 emmetropic subjects was measured for an array of numbers located at -1, -3 and -5 dioptres using an objective infra-red optometer. Responses were compared for passive (reading numbers) and active (adding numbers) conditions. The imposition of mental effort induced a significant increase in mean response for the -1 D stimulus, a response equivalent to the passive condition at -3 D and a reduction in response at -5 D. Mental effort induced similar responses for the -1 D and -3 D locations when sympathetic innervation to the ciliary muscle was blocked with the beta-receptor antagonist timolol maleate. Responses for the -5 D location were, however, significantly increased. It is proposed that sympathetic inhibition can modify the effect of mental effort on near accommodative responses.
Bullimore
M A
MA
Department of Vision Sciences, Aston University, Birmingham, UK.
Gilmartin
B
B
D000065:Accommodation, Ocular; D000328:Adult; D000704:Analysis of Variance; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D012030:Refractive Errors / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013850:Thinking / Q000502:physiology*; D013999:Timolol / Q000494:pharmacology
D013999:Timolol