title: Refractive change in response to acute hyperbaric stress in refractive surgery patients.
abstract: OBJECTIVE
  To determine whether acute hyperbaric stress affects visual acuity or refractive power after keratorefractive surgery.
  
  
  METHODS
  Clinical multiplace hyperbaric chamber and ophthalmology clinic, University of California, San Diego, California, USA.
  
  
  METHODS
  This prospective convenience sample study included 3 groups: 3 patients who had had bilateral myopic radial keratotomy (RK); 2 who had had bilateral myopic laser in situ keratomileusis (LASIK); and 4 control subjects who had no previous corneal refractive surgery or ocular pathology but had a myopic refractive error (-1.25 to -8.38 diopters [D]) similar to that in the treated patients before refractive surgery. One additional patient had had unilateral LASIK only and was included in the LASIK and control groups. Best spectacle-corrected visual acuity (BSCVA), manifest spherocylindrical refractive error, and intraocular pressure were measured at baseline, at 4 atmospheres absolute (atm abs), and on return to ambient pressure. Corneal pachymetry and keratometry were measured at baseline and on return to ambient pressure.
  
  
  RESULTS
  The mean BSCVA changed from 0.06 logMAR (20/25 Snellen equivalent) at baseline to 0.10 logMAR (20/25) at 4 atm abs in the RK group and from 0.00 logMAR (20/20) to -0.06 logMAR (20/15) in the LASIK group; it did not change in the control group. The mean refractive error changed from 0.25 D at baseline to 0.50 D at 4 atm abs in the RK group, from -0.90 to -1.02 D in the LASIK group, and from -4.58 to -4.53 D in the control group.
  
  
  CONCLUSIONS
  Acute hyperbaric stress did not appear to alter refractive power after corneal surgery.
authors.affiliation: University of Pennsylvania School of Medicine, Department of Emergency Medicine, Institute for Environmental Medicine, Philadelphia, Pennsylvania 19104-6068, USA.
authors.forename: Enoch T
authors.initials: ET
authors.lastname: Huang
authors.forename: Michael D
authors.initials: MD
authors.lastname: Twa
authors.forename: David J
authors.initials: DJ
authors.lastname: Schanzlin
authors.forename: Karen B
authors.initials: KB
authors.lastname: Van Hoesen
authors.forename: MaryAnn
authors.initials: M
authors.lastname: Hill
authors.forename: Mark I
authors.initials: MI
authors.lastname: Langdorf
mesh_terms: D000328:Adult; D001274:Atmospheric Pressure; D003315:Cornea / Q000601:surgery*; D004242:Diving; D005139:Eyeglasses; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D007646:Keratotomy, Radial; D053685:Laser Therapy; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery*; D012016:Reference Values; D012029:Refraction, Ocular; D013312:Stress, Physiological / Q000503:physiopathology*; D014792:Visual Acuity