title: Four-year visual outcomes after photorefractive keratectomy in pilots with low-moderate myopia.
abstract: BACKGROUND
  The photorefractive keratectomy (PRK) is approved for Air Force pilots in several nations. The occupational environments of pilots in the Air Force are unique, including extremely high altitude, low oxygen tension, high ultraviolet light exposure and high G-force load. The short-term efficacy and safety of PRK for pilots are documented. However, the study for long-term visual and refractive outcomes of PRK in pilots is limited.
  
  
  OBJECTIVE
  To investigate the long-term visual and refractive outcomes in a 4-year follow-up period after PRK in pilots with low to moderate myopia.
  
  
  METHODS
  Thirty-eight eyes of 20 subjects that underwent PRK and recruited to Air Force pilot were evaluated preoperatively and at 3, 6, 12, 24, and 48 months postoperatively.
  
  
  RESULTS
  The mean patient age was 21.42±0.75 years. The mean preoperative manifest refraction spherical equivalent (SE) was -1.51±1.15 diopters (D). At 4 years postoperatively, the mean SE was -0.29±0.51, 89.5% of eyes achieved 20/20 or better Snellen uncorrected visual acuity, 71.1% of eyes were within ±0.50 D of emmetropia. The refraction stabilised by 6 months and was maintained up to the 4-year follow-up stage.
  
  
  CONCLUSIONS
  PRK for pilots with low to moderate myopia is safe and effective in the long term. High-altitude environmental stress exposure has no effect on the refractive stability after PRK.
  
  
  BACKGROUND
  ROKAF-ASMC-2015-IRB-002.
authors.affiliation: Department of Ophthalmology, Aerospace Medical Center, Republic of Korea Air Force, Cheongju-si, Korea.
authors.forename: Chan Hee
authors.initials: CH
authors.lastname: Moon
mesh_terms: D000401:Aircraft; D000531:Altitude; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008889:Military Personnel; D009216:Myopia / Q000145:classification / Q000503:physiopathology* / Q000601:surgery*; D016273:Occupational Exposure; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*; D055815:Young Adult
keywords: Optics and Refraction