During hand neutralization, will a plus lens show with motion or against motion?

During hand neutralization, will a plus lens show with motion or against motion?

• A. With
• B. Against
• C. Neutral
• D. Neither

Answer: (B)

In hand neutralization, the direction you see the retinoscopic reflex move depends on where the eye’s far point sits relative to your retinoscope. Adding a lens in front of the eye shifts that far point. A plus lens makes light converge more, moving the far point forward toward the eye. At the usual working distance, this forward shift causes the reflex to move opposite to the streak you’re sweeping with the retinoscope. So the reflex appears to move against the motion you’re observing. This is why a plus lens will show against motion during hand neutralization. If a minus lens were used, you’d expect to see with motion instead.

In hand neutralization, the direction you see the retinoscopic reflex move depends on where the eye’s far point sits relative to your retinoscope. Adding a lens in front of the eye shifts that far point.

A plus lens makes light converge more, moving the far point forward toward the eye. At the usual working distance, this forward shift causes the reflex to move opposite to the streak you’re sweeping with the retinoscope. So the reflex appears to move against the motion you’re observing. This is why a plus lens will show against motion during hand neutralization. If a minus lens were used, you’d expect to see with motion instead.