Definition
A vision correction method in which one contact lens corrects the wearer's distance vision and the other corrects near vision, allowing each eye to specialize at a different focal range. The brain blends the two images, but at any given moment only one eye is providing a sharp image for a given distance. The FAA does not approve monovision contact lenses for pilots while flying because they degrade depth perception and slow the eyes' ability to adjust between distances.
Plain English
A setup where one eye wears a contact lens for seeing far away and the other eye wears a lens for seeing up close. It works for everyday life, but it causes problems in the cockpit because both eyes no longer work together the same way at every distance.
Context Anchor
Seen in night vision and pilot medical discussions, especially when considering how corrective lenses affect vision in the cockpit.
Derivation
Mono- comes from Greek monos, meaning 'one' or 'single.' Vision comes from Latin videre, 'to see.' So 'monovision' literally means 'single-eye seeing' -- each eye is set up to see at one distance rather than both eyes working together across all distances.
Why Pilots Care
They reduce binocular depth perception, increasing risk during night approaches and landings where accurate distance judgment is essential.
Grounding Statement
At night, if one eye is focused for the runway lights and the other is focused for the panel, the brain may have to work harder to combine the picture.
Intuition Check
Monovision does not mean seeing with only one eye. It means both eyes are used, but each eye is corrected for a different distance.
Example Sentence 1
During his medical, the pilot was reminded that his monovision contact lenses were fine for daily wear but could not be used while flying.
Example Sentence 2
During the preflight briefing the instructor noted that monovision contact lenses can create problems when judging runway distance at night.