During NRA/PRA testing, what must the patient use to keep the target single?

During NRA/PRA testing, what must the patient use to keep the target single?

• A. Vergence reserves
• B. Accommodation
• C. Pupil dilation
• D. Suppression only

Answer: (A)

During NRA/PRA testing, keeping the target single relies on the eyes’ fusional vergence system. As the clinician changes accommodation demand with lenses, the eyes must adjust convergence or divergence to maintain fusion. This ability to compensate with vergence reserves is what allows a single image to be maintained, even when accommodation is being stimulated or relaxed. Accommodation alone can’t guarantee single vision if the vergence system can’t supply the needed convergence or divergence; pupil size or suppression aren’t the mechanisms at play here. So the patient is using vergence reserves to keep the target single.

During NRA/PRA testing, keeping the target single relies on the eyes’ fusional vergence system. As the clinician changes accommodation demand with lenses, the eyes must adjust convergence or divergence to maintain fusion. This ability to compensate with vergence reserves is what allows a single image to be maintained, even when accommodation is being stimulated or relaxed. Accommodation alone can’t guarantee single vision if the vergence system can’t supply the needed convergence or divergence; pupil size or suppression aren’t the mechanisms at play here. So the patient is using vergence reserves to keep the target single.