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Voluntary effort as a stimulus to accommodation and vergence
1United States Air Force School of Aerospace Medicine, Radiation Sciences Division, Brooks Air Force Base, Texas.
Investigative Ophthalmology & Visual Science
|November 1, 1988
Summary
Voluntary effort primarily adjusts the focusing response (accommodation) during near vision tasks. The ratio of accommodation to vergence changes matched the accommodative vergence/accommodation (AC/A) ratio, not the vergence accommodation/vergence (CA/C) ratio.
Area of Science:
- Ophthalmology
- Neuroscience
- Vision Science
Background:
- Voluntary effort can modify visual responses like accommodation and vergence.
- Understanding the interplay between accommodation and vergence during voluntary effort is crucial for visual neuroscience.
Purpose of the Study:
- To investigate the cross-coupling interactions between accommodative vergence/accommodation (AC/A) and vergence accommodation/vergence (CA/C) during voluntary effort.
- To determine whether voluntary near response adjustments align with AC/A or CA/C ratios.
Main Methods:
- Simultaneous measurement of accommodation and vergence using a dual Purkinje image eye tracker and infrared optometer.
- Subjects viewed a Maltese cross monocularly through a pinhole pupil.
- Subjects made voluntary efforts to imaginary changes in target distance.
Main Results:
- The ratio of accommodation and vergence evoked by voluntary efforts was similar to the response AC/A ratio.
- The evoked response ratio differed significantly from the response CA/C ratio.
- One subject demonstrated isolated voluntary accommodation without vergence change when one eye was occluded.
Conclusions:
- Voluntary effort in the near response primarily adjusts the accommodation (focusing) system.
- The findings suggest a dominant role for the AC/A mechanism in voluntary visual adjustments.
- An exceptional case highlights potential individual variability in oculomotor control.