Definition
The narrowing of the pupil of the eye in response to bright light, reducing the amount of light entering the retina.
Plain English
When the eye is exposed to bright light, the pupil shrinks to a smaller size to let in less light.
Context Anchor
Seen in night vision discussions when learning how the eye reacts to cockpit lighting, flashlights, landing lights, or other bright lights at night.
Derivation
From the Latin 'constringere,' meaning 'to draw tight' or 'to bind together.' In the eye, it describes the iris drawing the pupil tight into a smaller opening.
Why Pilots Care
Knowing how constriction works helps pilots avoid bright lights that reset night vision and delay dark adaptation.
Grounding Statement
If a bright light hits your eyes during a night flight, your pupils constrict and your night vision may take time to recover.
Intuition Check
Constriction does not mean the eye is damaged or tense. Here it simply means the pupil gets smaller.
Example Sentence 1
Looking at a bright cockpit light at night caused pupil constriction, and the pilot lost some of the dark adaptation built up during cruise.
Example Sentence 2
Bright landing lights caused temporary constriction, so the pilot waited for the eyes to readjust before taxiing in the dark.