According to the phi phenomenon, during a subjective cover test, a patient with an eso deviation would view the paddle motion in which direction relative to the deviation?

According to the phi phenomenon, during a subjective cover test, a patient with an eso deviation would view the paddle motion in which direction relative to the deviation?

• A. Same direction
• B. Opposite direction
• C. No movement
• D. Upward

Answer: (B)

The test relies on the phi phenomenon, where the perceived motion of a light target is opposite to the direction the eye actually moves to re-fixate. In an eso deviation, the eye turns inward and then moves to re-fixate toward the nose. Because of phi, the paddle’s motion is perceived in the opposite direction—outward relative to the deviation. So the paddle appears to move in the opposite direction to the eye’s misalignment. The other directions don’t fit this perceptual illusion: the motion isn’t in the same direction as the deviation, it isn’t absent, and vertical movement isn’t implied by a horizontal inward turn.

The test relies on the phi phenomenon, where the perceived motion of a light target is opposite to the direction the eye actually moves to re-fixate. In an eso deviation, the eye turns inward and then moves to re-fixate toward the nose. Because of phi, the paddle’s motion is perceived in the opposite direction—outward relative to the deviation. So the paddle appears to move in the opposite direction to the eye’s misalignment. The other directions don’t fit this perceptual illusion: the motion isn’t in the same direction as the deviation, it isn’t absent, and vertical movement isn’t implied by a horizontal inward turn.