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AI.II.B.R2FAA-S-ACS-25 · Nov 2023Risk management

Relaxed intermediate focal distance.

ACS element text (the applicant demonstrates understanding of)

Relaxed intermediate focal distance.

Bottom line

Empty-field myopia causes the eyes to relax and seek a comfortable focal distance that may range from 10 to 30 feet, which means looking without seeing, and that is dangerous. Empty-field myopia usually occurs when flying above the clouds or in a haze layer that provides nothing specific to focus on outside the aircraft. Searching out and focusing on distant light sources, no matter how dim, helps prevent the onset of empty-field myopia.

FAA references

  1. AIM 8-1-6 (Vision in Flight) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
  2. AC 90-48, para. 8.1.5 — AC No: 90-48E
  3. PHAK ch. 17 (p. 17-22) — FAA-H-8083-25C (2023)
  4. AFH ch. 1 (p. 1-11) — FAA-H-8083-3C
  5. AIM 4-4-15 (Use of Visual Clearing Procedures and Scanning Techniques) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
  6. PHAK ch. 14 (p. 14-28) — FAA-H-8083-25C (2023)
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