Panum's Region of Binocular Single Vision and Stereopsis

What is the horopter?

The locus of points in space that fall on corresponding retinal points and are seen singly.

What happens to objects off the horopter?

They fall on disparate points and may produce diplopia.

Define Panum’s region.

The small region around the horopter where slight retinal disparity still allows binocular fusion

Are Panum’s areas purely retinal?

No — they are better considered cortical binocular interaction zones.

What did Hubel & Wiesel demonstrate?

Presence of binocular and monocular cells in the visual cortex.

Name the four neuronal classes involved in binocular vision.

1. Binocular corresponding

2. Binocular disparate

3. Monocular left

4. Monocular right

When is single vision produced?

When corresponding neurons fire with same visual direction coding.

What causes depth perception?

Activation of disparity-sensitive binocular neurons.

What happens when disparity exceeds Panum’s limit?

Diplopia occurs.

Panum’s area size at fovea?

6–15 sec arc

In periphery for panum fusion?

30–40 sec arc

Maximum horizontal extent (low freq) for panum arc?

20 min arc

Minimum size at high frequency?

1.5 min arc

What are D1 and D2 cells?

Disparity detectors (depth detectors).

Why do two eyes produce depth?

Because lateral separation creates slightly different retinal images.