The Glenn A. Fry award lecture: adaptive regulation of accommodative vergence and vergence accommodation

Area of Science:

• Ophthalmology and Vision Science
• Neuroscience
• Physiology

Background:

• Tonic accommodation and vergence are crucial for maintaining visual stability.
• Understanding their adaptive mechanisms is key to addressing visual disorders.

Purpose of the Study:

• To investigate the adaptive changes in tonic accommodation and vergence.
• To explore the relationship between tonic and phasic control mechanisms.
• To analyze the temporal responses of accommodation-vergence interactions.

Main Methods:

• Objective infrared optometry was used to measure accommodation in an open-loop state.
• Monocular adaptation to minus lenses and base-out prisms was employed.
• Sinusoidal variations in blur and disparity were used to assess temporal frequency responses of AC/A and CA/C ratios.

Main Results:

• Adaptation to minus lenses increased tonic accommodation, while adaptation to prisms increased esophoria.
• Accommodative vergence and vergence accommodation showed responsiveness to higher temporal frequencies.
• Removing negative feedback increased AC/A and CA/C ratios, with nonlinear increases observed with stimulus amplitude.

Conclusions:

• An inverse complementary relationship exists between adaptable tonic vergence/accommodation and their respective ratios.
• Adaptable tonic elements sustain motor responses initiated by phasic elements.
• AC/A and CA/C ratios decrease over time as control shifts from phasic to adaptable tonic mechanisms.