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The effect of vergence adaptation on convergent accommodation
1Department of Vision Sciences, Aston University, Birmingham, UK.
Summary
Both fast reflex and slower adaptive vergence responses stimulate convergent accommodation (CA) during near vision tasks. This suggests a dual mechanism maintains CA, impacting accommodation-vergence interaction models.
Area of Science:
- Ophthalmology
- Neuroscience
- Vision Science
Background:
- Accommodation and vergence are crucial for clear binocular vision.
- Understanding their interaction is key to explaining visual performance and disorders.
Purpose of the Study:
- To determine if tonic vergence maintains convergent accommodation (CA) during sustained near vision.
- To investigate the roles of reflex and adaptive vergence in stimulating CA.
Main Methods:
- Objective infra-red optometry measured accommodative response in 10 emmetropic subjects.
- Vergence was stimulated using base-out prisms during a 3-minute near task.
- Accommodation loop was opened using pinholes; heterophoria was measured pre- and post-task.
Main Results:
- Adaptation to the vergence stimulus was confirmed by heterophoria measurements.
- No significant reduction in induced convergent accommodation (CA) was observed during the task.
- Both reflex and adaptive vergence contributed to stimulating CA.
Conclusions:
- Sustained near vision involves both reflex and adaptive vergence mechanisms.
- These vergence responses act as stimuli for convergent accommodation (CA).
- Findings inform models of accommodation-vergence interaction.