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Vertical vergence in nonhuman primates depends on horizontal gaze position
1College of Optometry, University of Houston , Houston , TX.
Strabismus
|June 22, 2019
Summary
Vertical fusion capability varies with eye position in nonhuman primates. Extraocular muscle involvement in vertical vergence appears idiosyncratic, likely involving a combination of muscles.
Area of Science:
- Ophthalmology
- Neuroscience
- Primate Vision
Background:
- Vertical vergence is crucial for maintaining binocular single vision.
- The specific extraocular muscles (EOMs) responsible for vertical vergence at different gaze positions are not fully understood.
Purpose of the Study:
- To compare vertical fusion capability across various orbital eye positions in nonhuman primates.
- To investigate which EOMs mediate vertical vergence based on fusion capabilities.
Main Methods:
- Two nonhuman primates (M1, M2) underwent a vertical vergence task with dichoptic stimuli.
- Scleral search coils tracked eye movements while vertical disparity was introduced.
- Vertical fusion amplitude and vergence were measured at different horizontal eye positions.
Main Results:
- Vertical fusion capability varied significantly with orbital eye position in both subjects.
- Individual differences were observed, with one primate showing reduced fusion when the right eye was abducted, and the other when it was adducted.
- One primate demonstrated greater vertical fusion capability at near gaze.
Conclusions:
- Extraocular muscle involvement in vertical fusional vergence is idiosyncratic.
- Vertical vergence likely results from a weighted combination of multiple cyclovertical muscles, varying between individuals.
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