Definition
Thin corrective or cosmetic lenses worn directly on the surface of the eye. In aviation, their use is a medical and operational consideration because dryness, glare sensitivity, and reduced low-light performance can affect a pilot's vision, particularly at night and at altitude where cabin air is dry and oxygen levels are reduced.
Plain English
Small lenses that sit on the eye to correct vision instead of glasses. Pilots need to be aware that they can dry out, fog, or reduce night vision in the cockpit environment.
Context Anchor
Seen in night vision and pilot health discussions, especially when considering how well a pilot can see cockpit instruments, lights, terrain, and the runway at night.
Derivation
From Latin contactus, meaning 'touching,' because the lens rests directly on the eye. The name itself signals the key difference from glasses: it is in physical contact with the eye, which is why dryness and oxygen flow to the cornea matter in flight.
Why Pilots Care
Contact lenses must meet the same FAA vision standards as glasses for medical certification, and improper fit can lead to discomfort or reduced vision in low-light or high-altitude conditions.
Intuition Check
Do not assume contact lenses are just eyeglasses without frames. In the cockpit, they can dry out, move, or irritate the eye, which can reduce vision when clear sight is critical.
Example Sentence 1
Because she wore contact lenses, she kept a spare pair of glasses in her flight bag in case her eyes dried out on a long night cross-country.
Example Sentence 2
Before takeoff the pilot checked that the contact lenses were properly seated to avoid any irritation under night lighting conditions.