title: Corneal hysteresis, resistance factor, topography, and pachymetry after corneal lamellar flap.
abstract: OBJECTIVE
  To measure prospectively the early changes in corneal hysteresis, topography, and pachymetry after the creation of a stromal flap cut without laser photoablation.
  
  
  METHODS
  A 37-year-old man was referred for a bioptic procedure to correct for compound myopic astigmatism in the left eye. A 159-microm-thick 8x8.5-mm superior hinged flap was created with a mechanical microkeratome in the left cornea. Changes in the corneal hysteresis, corneal resistance factor, Goldmann correlated intraocular pressure (lOP), corneal compensated IOP, anterior and posterior topography, and optical and ultrasound pachymetry were monitored prospectively before and at 1 hour, 1 day, 5 days, and 25 days after flap creation. The right eye served as a control.
  
  
  RESULTS
  In the left eye, corneal hysteresis and corneal resistance factor decreased immediately after the flap cut and remained lower than preoperatively at 1 hour, 1 day, 5 days, and 25 days. Corneal compensated IOP varied significantly less than Goldmann correlated IOP in both eyes. Central flattening of the horizontal meridians was observed on the difference topography maps. The values of the left eye posterior best fit sphere increased after the flap cut. Increased central corneal thickness occurred immediately after the flap cut and decreased over time without returning to its preoperative value.
  
  
  CONCLUSIONS
  The creation of a stromal flap can modify the biomechanical properties of the cornea, including a reduction in corneal hysteresis. The topographic changes were consistent with previously reported cases of flap cut in normal corneas.
authors.affiliation: Rothschild Foundation, 25 rue Manin, 75019 Paris, France. gatinel@aol.com
authors.forename: Damien
authors.initials: D
authors.lastname: Gatinel
authors.forename: Slim
authors.initials: S
authors.lastname: Chaabouni
authors.forename: Pierre-Alexandre
authors.initials: PA
authors.lastname: Adam
authors.forename: Jacques
authors.initials: J
authors.lastname: Munck
authors.forename: Michel
authors.initials: M
authors.lastname: Puech
authors.forename: Thanh
authors.initials: T
authors.lastname: Hoang-Xuan
mesh_terms: D000328:Adult; D015858:Anisometropia / Q000150:complications / Q000473:pathology / Q000601:surgery*; D001251:Astigmatism / Q000150:complications / Q000473:pathology / Q000601:surgery*; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D019781:Corneal Topography; D016039:Corneal Transplantation / Q000000981:diagnostic imaging / Q000379:methods* / Q000473:pathology; D004548:Elasticity; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D009216:Myopia / Q000150:complications / Q000473:pathology / Q000601:surgery*; D013524:Surgical Flaps; D041623:Tomography, Optical Coherence; D014463:Ultrasonography