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Related Experiment Videos

Tonic accommodation, cognitive demand, and ciliary muscle innervation.

M A Bullimore, B Gilmartin

    American Journal of Optometry and Physiological Optics
    |January 1, 1987
    PubMed
    Summary

    Cognitive tasks can shift tonic accommodation (TA) by up to +1 D, primarily through parasympathetic pathways. Sympathetic blockade with timolol maleate altered these shifts, especially in subjects with higher initial TA.

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    Area of Science:

    • Ophthalmology
    • Neuroscience
    • Physiology

    Background:

    • Tonic accommodation (TA) is the resting state of the eye's accommodative system.
    • Cognitive load is known to influence physiological processes, including visual functions.
    • The role of autonomic innervation (sympathetic and parasympathetic) in cognitive-induced TA shifts requires further elucidation.

    Purpose of the Study:

    • To investigate the relationship between cognitive-induced shifts in tonic accommodation (TA) and ciliary muscle innervation.
    • To determine the influence of sympathetic blockade on cognitive-induced TA shifts.

    Main Methods:

    • Utilized an infrared optometer to measure tonic accommodation in 20 emmetropic male volunteers.
    • Employed a double-masked protocol with high and low cognitive load tasks (reverse counting).

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  • Administered 0.5% timolol maleate to block sympathetic innervation of the ciliary muscle.

    • Main Results:

    • High cognitive demand induced TA shifts of up to +1 D.
    • The effect of beta-antagonism (timolol) was insignificant for subjects with initial TA < 1.2 D.
    • Sympathetic antagonism significantly increased cognitive shifts in subjects with initial TA ≥ 1.2 D.

    Conclusions:

    • Cognitive-induced shifts in TA are predominantly mediated by parasympathetic pathways.
    • Sympathetic innervation may play an attenuating role in cognitive-induced TA shifts, particularly at higher initial TA levels.