title: Corneal biomechanical properties in eyes with no previous surgery, with previous penetrating keratoplasty and with deep anterior lamellar keratoplasty.
abstract: OBJECTIVE
  To compare the biomechanical properties of the cornea in eyes with no previous surgery, with keratoconus with previous penetrating keratoplasty (PK) and with keratoconus with previous deep anterior lamellar keratoplasty (DALK) using the Reichert Ocular Response Analyzer (ORA).
  
  
  METHODS
  One hundred twenty eyes of 120 patients were included in this prospective comparative study. Forty eyes were with no previous ocular surgery (group 1), 40 eyes were with previous PK for keratoconus (group 2), and 40 eyes were with previous DALK for keratoconus (group 3). Corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with ORA.
  
  
  RESULTS
  The CH and CRF values in group 2 were significantly lower than in group 1 and group 3 (p = 0.001). The CH and CRF values were similar in group 1 and group 3. There was no statistically significant difference between group 1 and 3.
  
  
  CONCLUSIONS
  Although the post-PK keratoconus cornea has weaker biomechanical properties, post-DALK keratoconus cornea is similar to normal cornea. A cornea weakened by keratoconus can be strengthened with lamellar keratoplasty.
authors.affiliation: Ophthalmology Clinic, Department of Ophthalmology, Haydarpasa Numune Education and Research Hospital, Tibbiye cad. Uskudar, 34668 Istanbul, Turkey. torunbanu@yahoo.com
authors.forename: Banu Torun
authors.initials: BT
authors.lastname: Acar
authors.forename: Mehmet Orcun
authors.initials: MO
authors.lastname: Akdemir
authors.forename: Suphi
authors.initials: S
authors.lastname: Acar
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000503:physiopathology / Q000601:surgery*; D015948:Keratoplasty, Penetrating / Q000379:methods*; D008297:Male; D011446:Prospective Studies