Convergence and divergence eye movements rotate around which axis in Listing's Plane?

• A. X axis
• B. Y axis
• C. W axis
• D. Z axis

Answer: (D)

Listing's Plane provides the reference for how the eyes rotate when moving from primary position. Any gaze that changes where you’re looking can be represented as a single rotation about an axis that lies in that plane. Convergence and divergence are vergence movements where the two eyes rotate toward or away from the nose, and in the NBEO coordinate framework used here that rotation is about an axis that sits in Listing's Plane—the Z axis.

Think of horizontal and vertical components in Listing's Plane as the X and Y directions, while the axis that runs within that plane for vergence corresponds to the Z axis. Rotating about this axis changes the alignment of the eyes to bring the objects into binocular focus without introducing torsion, which is why convergence/divergence align with the Z axis in Listing’s representation.