An adaptable association between vertical and horizontal vergence

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Vertical phoria represents a vergence error during monocular viewing.
• It plays a role in compensating for oculomotor system changes.
• Previous research linked vertical phoria to conjugate eye position.

Purpose of the Study:

• To investigate the difference in vertical phoria adaptation based on target separation (vertical vs. depth axis).
• To explore the association between vertical phoria and horizontal vergence.
• To understand the neural underpinnings of vertical vergence adaptation.

Main Methods:

• Adaptation of vertical phoria using vertically disparate targets separated along the depth axis versus the vertical axis.
• Measurement of vertical vergence aftereffects.
• Analysis of the dependency on horizontal vergence and conjugate eye position.

Main Results:

• Vertical phoria adaptation was significantly influenced by horizontal vergence.
• The vertical vergence aftereffect was approximately four times greater for targets separated along the depth axis compared to the vertical axis.
• Vertical phoria aftereffects were also induced by accommodative vergence.

Conclusions:

• Vertical phoria can be trained to vary with conjugate eye position.
• The oculomotor system exhibits cross-coupling between vertical vergence and systems controlling conjugate and horizontal vergence.
• This interaction may allow for correction of disturbances in supranuclear control regions.