Which statement about stereopsis is untrue?

Which statement about stereopsis is untrue?

• A. Testing for stereopsis should be done without spectacle correction.
• B. Stereopsis tests depth perception using binocular disparity cues.
• C. Stereopsis testing requires both eyes to be open and proper alignment.
• D. Stereopsis can be accurately assessed with one eye closed.

Answer: (D)

Stereopsis depends on input from both eyes to create depth through binocular disparity. When both eyes are open and properly aligned, the brain fuses slightly different images to perceive how far away objects are. If one eye is closed, there’s no paired image to compare, so true stereopsis can’t be measured—the test would rely on monocular cues like perspective or shading, which do not reflect binocular depth perception. That’s why the statement claiming you can accurately assess stereopsis with one eye closed is not true. The other ideas fit with how stereopsis is assessed: testing is typically done without spectacle correction to avoid any optical effects that could alter disparity; stereopsis tests specifically measure depth from binocular disparity cues; and valid testing requires both eyes open with proper alignment to ensure the brain can fuse the images and provide an accurate measure of stereoacuity.

Stereopsis depends on input from both eyes to create depth through binocular disparity. When both eyes are open and properly aligned, the brain fuses slightly different images to perceive how far away objects are. If one eye is closed, there’s no paired image to compare, so true stereopsis can’t be measured—the test would rely on monocular cues like perspective or shading, which do not reflect binocular depth perception. That’s why the statement claiming you can accurately assess stereopsis with one eye closed is not true.

The other ideas fit with how stereopsis is assessed: testing is typically done without spectacle correction to avoid any optical effects that could alter disparity; stereopsis tests specifically measure depth from binocular disparity cues; and valid testing requires both eyes open with proper alignment to ensure the brain can fuse the images and provide an accurate measure of stereoacuity.