FAA Private Pilot Helicopter (PRH)Human FactorsHard
During a night flight over dark, featureless terrain with no ground lights or stars visible, a pilot scanning for traffic finds it difficult to focus on anything in the distance. Unknown to the pilot, his eyes have relaxed to a near focus of only 10 to 30 feet, causing him to miss an approaching aircraft's lights until very late. Which condition explains this?
- AAutokinesis
- BPresbyopia
- CHyperopia
- DEmpty-field myopia
Show answer & explanationAnswer & explanation
Correct answer: D. Empty-field myopia
Empty-field myopia occurs when there is nothing specific to focus on (dark, featureless sky or terrain), causing the eyes to default to a near resting focal distance of about 10-30 feet. This makes distant objects, like other aircraft, effectively out of focus and harder to detect.
Why the other options are wrong
- A. Autokinesis is the illusion of a stationary light appearing to move, not a focusing problem.
- B. Presbyopia is age-related loss of near-focus ability, not caused by featureless fields.
- C. Hyperopia is farsightedness, a permanent vision condition unrelated to featureless scanning.
Empty-Field Myopia
A condition where, in the absence of visual references, the eyes relax to a near focal distance of 10-30 feet, making distant objects like aircraft appear out of focus and harder to see.
- Occurs in dark, featureless sky or over water/terrain at night
- Eyes default to near focus without conscious effort
- Pilots should consciously refocus at varying distances during scans
Memory trick: Nothing to see, eyes settle near — traffic sneaks in unseen.