Which description is more closely related to points within the retina?

• A. Panum's fusional area
• B. Panum's fusional space
• C. Horopter
• D. Vergence range

Answer: (A)

Panum's fusional area is the region around corresponding retinal points where small disparities between the two eyes’ images can still be fused into a single percept. This makes it a retinal concept, describing how close on the retina the images can be while remaining single.

The other ideas focus on space or eye movements rather than retinal locations. Panum's fusional space refers to the depth region in space where fusion occurs, not to retinal points. The horopter is the set of points in space that project to corresponding retinal points, a spatial relationship rather than a retinal zone. Vergence range concerns how far the eyes can rotate to maintain single vision, which is about motor ability, not retinal wiring for fusion.