How do deficits in saccade and pursuit affect binocular function?

• A. They improve fusion
• B. They hinder rapid alignment and stabilization required for fusion, increasing diplopia or suppression
• C. They have no effect
• D. They only affect depth perception

Answer: (B)

Efficient binocular fusion depends on quick, precise eye movements to align the eyes and keep images stable as targets move. Saccades rapidly reposition the gaze, and pursuit maintains a moving target on the fovea. When these movements are deficient, the eyes can’t align quickly or stay aligned during motion, so the two eyes don’t form a single fused image. That misalignment leads to diplopia (double vision) or, to avoid seeing two images, the brain may suppress one eye’s image, which undermines binocular sharing and can reduce depth perception. Therefore, deficits in saccade and pursuit disrupt the rapid alignment and stabilization needed for fusion, making diplopia or suppression more likely.