Definition
A physical symptom of fatigue in which the eyes intermittently lose and regain sharp focus, so objects such as instruments, charts, or distant traffic appear briefly clear and then briefly blurry without the pilot consciously changing where they are looking.
Plain English
Your vision keeps going fuzzy and then sharp again on its own. One moment the gauges look crisp, the next they look soft, and you didn't do anything to cause the change.
Context Anchor
Seen in fatigue and situational awareness training, especially when discussing warning signs that a pilot, student, or instructor should notice before performance gets worse.
Why Pilots Care
It indicates accumulating fatigue that degrades situational awareness and raises the chance of missing critical flight information.
Grounding Statement
If the panel, chart, runway, or page keeps becoming blurry and then clear again, treat it as a possible fatigue warning sign, not just an annoyance.
Intuition Check
Do not assume this only means a person needs glasses. In this FAA context, eyes going in and out of focus can be a warning sign that fatigue is reducing the person’s ability to stay alert and visually steady.
Example Sentence 1
Halfway through the long cross-country, the pilot noticed his eyes going in and out of focus on the airspeed indicator and decided to divert for a rest stop.
Example Sentence 2
The instructor ended the lesson early when the student reported their eyes going in and out of focus while reading the approach plate.