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Blink rate decreases with eyelid squint.
James E Sheedy1, Sowjanya Gowrisankaran, John R Hayes
1The Ohio State University College of Optometry, Columbus, Ohio 43210, USA. jsheedy@optometry.osu.edu
Summary
Voluntary eyelid squint significantly reduces blink rate, with higher squint levels causing greater reductions. This study confirms eyelid squint
Area of Science:
- Ophthalmology
- Neuroscience
- Biomechanics
Background:
- Eyelid squint is hypothesized to improve vision under optical defocus or glare.
- Reduced blink rate is associated with dry eye symptoms and asthenopia (eye strain).
- The relationship between voluntary eyelid squint and blink rate requires investigation.
Purpose of the Study:
- To investigate the effect of voluntary eyelid squint on blink rate.
- To examine electromyography (EMG) changes in the orbicularis oculi muscle during squinting.
- To explore the potential link between eyelid squint, blink inhibition, and asthenopia.
Main Methods:
- Ten subjects (18-38 years) performed voluntary squint at 0%, 5%, 20%, 35%, and 50% of maximum.
- Orbicularis oculi muscle EMG was recorded using surface electrodes.
- Ocular aperture and blink activity were measured using an eye tracker and video recording.
Main Results:
- Significant changes in ocular aperture, EMG power, and amplitude were observed at all squint levels (p<0.0001).
- Mean squint responses ranged from 24% to 53% for target levels of 5% to 50%.
- Blink rate significantly decreased with increasing squint levels, from 15 blinks/min at 0% to 4 blinks/min at 50% squint (p<0.0001).
Conclusions:
- Voluntary eyelid squint significantly reduces blink rate by 50% or more, depending on the attempted level.
- EMG signals from the orbicularis oculi muscle reliably indicate eyelid squint.
- Further research is needed to determine if involuntary squint affects blink rate similarly.