Adaptive control of vergence in humans

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Vergence eye alignment is crucial for stereo-depth perception, minimizing horizontal, vertical, and cyclodisparities.
• Voluntary control is limited to horizontal vergence, while vertical vergence and cyclovergence are guided by couplings with version and horizontal vergence.

Purpose of the Study:

• To investigate if adaptive couplings for vertical vergence and cyclovergence can be modified by sensory demands on binocular vision.
• To understand the neural and mechanical basis of vergence adaptation.

Main Methods:

• Stimulated vertical vergence using aniseikonic lenses to induce vertical disparity in tertiary gaze.
• Stimulated cyclovergence using cyclodisparities that varied with gaze elevation and convergence angle.
• Modeled adaptive couplings using passive orbital mechanics and active gain control.

Main Results:

• Vertical vergence adapted within an hour, showing nonconcomitant changes in vertical phoria dependent on vertical eye position.
• Cyclovergence adapted within two hours, exhibiting nonconcomitant changes in cyclophoria dependent on gaze elevation and convergence.
• Adaptation involved nonconcomitant changes in phoria that varied with eye position and gaze parameters.

Conclusions:

• Vergence adaptation is a calibration process adjusting innervation for all vergence components (horizontal, vertical, torsion).
• Passive orbital mechanics and active gain control contribute to precise vertical vergence and cyclovergence.
• This adaptation optimizes binocular alignment under open-loop conditions based on perceived spatial location.