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Human dynamic closed-loop accommodation augmented by sympathetic inhibition.

H M Culhane1, B Winn, B Gilmartin

  • 1Department of Optometry, University of Bradford, West Yorkshire, United Kingdom.

Investigative Ophthalmology & Visual Science
|May 11, 1999
PubMed
Summary
This summary is machine-generated.

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Topical phenylephrine hydrochloride increased accommodative gain in humans by augmenting alpha1-inhibitory sympathetic activity. This study investigated the effect of modulating alpha1-adrenoceptor activity on dynamic accommodation.

Area of Science:

  • Ophthalmology
  • Neuroscience
  • Pharmacology

Background:

  • A ciliary alpha-adrenoceptor mechanism for accommodation has been proposed.
  • This mechanism involves alpha1-inhibitory receptors in the human ciliary muscle.

Purpose of the Study:

  • To investigate the effect of modulating alpha1-adrenoceptor activity on dynamic accommodation.
  • To assess the impact of phenylephrine hydrochloride on the closed-loop accommodative process.

Main Methods:

  • 10 visually normal subjects underwent monocular accommodation measurements.
  • Dynamic tracking infrared optometry recorded responses to sinusoidal and stepwise visual stimuli.
  • Accommodation was measured after saline control and phenylephrine hydrochloride instillation.

Related Experiment Videos

Main Results:

  • Phenylephrine hydrochloride significantly reduced accommodative amplitude but increased pupil size.
  • No significant changes in step-response dynamics or phase lag were observed.
  • Accommodative gain significantly increased in low and midtemporal frequencies.

Conclusions:

  • Augmenting alpha1-inhibitory sympathetic activity increases accommodative gain in humans.
  • Findings align with previous animal studies on alpha1-adrenoceptor effects on accommodation.
  • This study provides the first human evidence for this accommodative mechanism.