Definition
The slight difference between the two images formed on the retinas of the left and right eyes when viewing the same object. Because the eyes are separated horizontally, each eye sees the scene from a slightly different angle, and the brain combines these two images to perceive depth and judge distance.
Plain English
Your two eyes see the world from slightly different positions, so each eye gets a slightly different picture. Your brain compares those two pictures to work out how far away things are.
Context Anchor
Seen in aviation medical, human factors, and vision discussions, especially when learning how pilots judge depth during landing, taxiing, or close visual maneuvering.
Derivation
From Latin rete (net) — the retina is the net-like layer at the back of the eye. Disparity comes from Latin disparitas, meaning 'unevenness' or 'difference.' So the term literally means 'a difference between the two retinas' — which is exactly what gives the brain depth information.
Why Pilots Care
Supports accurate depth judgment during landing, taxiing, and formation flight where visual cues are primary.
Analogy
Hold one finger in front of your face and close one eye, then the other. The finger seems to shift because each eye is seeing it from a slightly different place; that shift is retinal disparity.
Grounding Statement
When an object is close, the two eyes receive more noticeably different views; when it is far away, the two views are almost the same.
Intuition Check
Retinal disparity does not mean an eye problem by itself. In this context, it means the normal difference between what each eye sees.
Example Sentence 1
Retinal disparity helps a pilot judge the closing distance to the runway during the flare.
Example Sentence 2
Loss of retinal disparity cues in low light increases reliance on other visual references.