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Effect of vergence adaptation on convergence-accommodation: model simulations.
Vidhyapriya Sreenivasan1, William R Bobier, Elizabeth L Irving
1School of Optometry, University of Waterloo, Waterloo, ON N2L3G1, Canada. vsreeniv@sciborg.uwaterloo.ca
IEEE Transactions on Bio-Medical Engineering
|July 2, 2009
Summary
Human visual system adaptation was studied using two models and empirical data. Vergence adaptation reduced exophoria and convergence-accommodation, with one model accurately predicting these changes over time.
Area of Science:
- Ophthalmology
- Neuroscience
- Biophysics
Background:
- Human visual system exhibits adaptation in accommodation and vergence mechanisms.
- Existing quantitative models for visual adaptation differ in their definition and impact of controller adaptation on cross-links between vergence and accommodation.
Purpose of the Study:
- Compare simulation results from two adaptation models with empirical data.
- Evaluate model prediction accuracy for visual adaptation effects during sustained near tasks.
Main Methods:
- Emmetropic adults performed sustained near tasks with +2D lens addition.
- Measured exophoria and convergence-accommodation (CA) responses.
- Compared empirical data with simulations from two theoretical control models.
Main Results:
- Sustained near viewing with +2D lenses initially increased exophoria and CA.
- Vergence adaptation subsequently reduced exophoria and CA.
- Both models agreed with vergence adaptation measures, but only one predicted the CA reduction time course.
Conclusions:
- The adaptation model incorporating phasic and tonic controllers best describes the empirical results.
- This model accurately predicts the interplay between vergence adaptation and convergence-accommodation dynamics.
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