Related Experiment Video
Updated: May 19, 2026

Simulating the Mechanics of Lens Accommodation via a Manual Lens Stretcher
Published on: February 23, 2018
The effect of phenylephrine on the ciliary muscle and accommodation
Kathryn Richdale1, Melissa D Bailey, Loraine T Sinnott
1College of Optometry, The State University of New York, New York, New York 10036, USA. KRichdale@SUNYopt.edu
Purpose:
To objectively measure changes in the human ciliary muscle dimensions in vivo after instillation of topical phenylephrine, a mydriatic and vasodilating agent.
Methods:
A cross-sectional study of 25 healthy young adults was conducted. Measurements of pupil size, accommodation, and ciliary muscle thickness were made both before and 30 min after instillation of 1% proparacaine and 2.5% phenylephrine. Accommodation was measured in three ways: subjectively using a push-up technique and Royal Air Force (RAF) rule, and objectively using both the Grand Seiko autorefractor and PowerRefractor. Images of the temporal ciliary muscle were acquired using the Visante Anterior Segment Optical Coherence Tomographer (OCT). Ciliary muscle images were objectively analyzed using a computer-based segmentation technique.
Results:
Amplitude of accommodation using the push-up test was reduced by about 1 D with phenylephrine (p < 0.001). Phenylephrine did not change the accommodative response to a 4 D Badal target as measured by either autorefraction or photorefraction (p > 0.30). There was statistically significant thickening of the anterior region and thinning of the posterior region of the ciliary muscle with accommodation (p < 0.001, all locations). Phenylephrine did not affect either baseline ciliary muscle thickness or the accommodative contraction of the muscle (p > 0.09).
Conclusions:
Low-dose phenylephrine does not affect ciliary muscle dimensions, ciliary muscle contractility, or accommodative response to a 4 D near target.
Related Concept Videos
Focusing of Light in the Eye
Direct-Acting Cholinergic Agonists: Pharmacological Actions
Open Angle Glaucoma: Treatment
Drugs such as carbonic anhydrase inhibitors, α2- and...
Direct-Acting Cholinergic Agonists: Therapeutic Uses
Cholinergic Antagonists: Pharmacological Actions
Gastrointestinal Effects: Antimuscarinics reduce gut contractions, increase gastric emptying, and slow intestinal transit. They partly inhibit gastric acid secretion...
Adrenergic Agonists: Mixed-Action Agents
Ephedrine and pseudoephedrine lack a catecholamine group, making them less susceptible to degradation by metabolic enzymes. They have increased oral bioavailability and lipophilicity, resulting in a longer duration of action. Their response is reduced by...

