Definition
A condition in which the eyes cannot adjust well to low-light conditions, making it difficult or impossible to see clearly at night or in dim light. It is most often caused by a deficiency of vitamin A, which the retina needs to produce the chemical (rhodopsin) used for low-light vision. It can also result from certain eye diseases or fatigue.
Plain English
A condition where a person cannot see well in the dark, even after their eyes have had time to adjust.
Context Anchor
Encountered in aeromedical discussions, night flying preparation, and decisions about whether a pilot is safe to fly after dark.
Why Pilots Care
A pilot with night blindness may be denied night flying privileges or require special medical evaluation to maintain certification.
Grounding Statement
A pilot may feel fine in daylight but struggle to pick out important shapes and lights once the flight is in darkness.
Intuition Check
Night blindness does not usually mean total blindness at night. It means reduced or unsafe vision in low-light conditions.
Example Sentence 1
The flight surgeon warned the student that mild night blindness from a poor diet could make landing at an unlit airstrip dangerous.
Example Sentence 2
Because of night blindness the applicant was limited to daytime operations only.