The Lang stereo test does not require glasses to see depth. Which statement is true about it?

The Lang stereo test does not require glasses to see depth. Which statement is true about it?

• A. It requires red-green glasses
• B. It uses random dot patterns
• C. It does not require glasses to see depth and uses ridged disparity
• D. It measures color vision

Answer: (C)

Depth is perceived in the Lang stereo test because the printed pattern contains ridged disparity. The slight physical relief creates two different views for the two eyes, and when the eyes fuse these views the brain interprets a depth difference, so you see the depth without any glasses. This is in contrast to tests that rely on colored filters (glasses) or on random-dot patterns to convey depth; Lang uses the ridges themselves rather than color or dot cues. It’s focused on stereopsis, not on color vision.

Depth is perceived in the Lang stereo test because the printed pattern contains ridged disparity. The slight physical relief creates two different views for the two eyes, and when the eyes fuse these views the brain interprets a depth difference, so you see the depth without any glasses. This is in contrast to tests that rely on colored filters (glasses) or on random-dot patterns to convey depth; Lang uses the ridges themselves rather than color or dot cues. It’s focused on stereopsis, not on color vision.