title: Recovery of corneal sensitivity to mechanical and chemical stimulation after laser in situ keratomileusis.
abstract: OBJECTIVE
  To evaluate the time course of changes in corneal sensitivity to mechanical and chemical stimuli produced by laser in situ keratomileusis (LASIK) in humans.
  
  
  METHODS
  We performed a cross-sectional study of 17 LASIK-operated eyes (VisX S2, equipped with version 2.50-3.10 software) and 15 control eyes of 17 individuals to evaluate regeneration of corneal sensitivity after LASIK. Gas pulses of variable flow and compositions were applied to the cornea by a non-contact gas esthesiometer. Mechanical stimuli consisted of air puffs at flows from 0 to 200 ml/min. Chemical stimulation was made with gas pulses containing 0% to 80% CO2 in air at subthreshold flow. Mechanical and chemical thresholds and intensity-response curves for the evoked sensations were determined prior to surgery, and 7 to 9 days, 3 to 5 months, and 1.5 to 2.5 years after surgery.
  
  
  RESULTS
  Corneal sensitivity to mechanical stimulation was enhanced 7 to 9 days after surgery but subsequently dropped markedly and remained significantly below control levels 3 to 5 months after LASIK. Sensitivity to both mechanical and chemical types of stimuli was close to normal 2 years postoperatively.
  
  
  CONCLUSIONS
  Corneal sensitivity decreased immediately after LASIK but mechanical sensitivity showed a transient hyperesthesia 7 to 9 days afterward. Subsequently, a long-lasting and deep hypoesthesia to mechanical and chemical stimuli was observed. Gas esthesiometry revealed that disturbances of corneal sensation still exist at times when coarse mechanical sensitivity appeared to be normal.
authors.affiliation: Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Campus de San Juan, San Juan de Alicante, Spain. juana.gallar@umh.es
authors.forename: Juana
authors.initials: J
authors.lastname: Gallar
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Acosta
authors.forename: Jukka A O
authors.initials: JA
authors.lastname: Moilanen
authors.forename: Juha M
authors.initials: JM
authors.lastname: Holopainen
authors.forename: Carlos
authors.initials: C
authors.lastname: Belmonte
authors.forename: Timo M T
authors.initials: TM
authors.lastname: Tervo
mesh_terms: D000328:Adult; D003315:Cornea / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation / Q000379:methods; D011184:Postoperative Period; D020127:Recovery of Function; D012030:Refractive Errors / Q000503:physiopathology; D054140:Refractive Surgical Procedures; D012677:Sensation / Q000502:physiology*; D012684:Sensory Thresholds; D013268:Stimulation, Chemical; D013314:Stress, Mechanical; D014792:Visual Acuity