title: Graft biomechanical properties after penetrating keratoplasty in keratoconus.
abstract: OBJECTIVE
  To measure corneal graft biomechanical properties after penetrating keratoplasty (PKP) in a group of keratoconic eyes using the ocular response analyzer (ORA) and to evaluate the relationship between donor size, donor-recipient disparity and central graft thickness (CGT), and ORA parameters.
  
  
  METHODS
  This cross-sectional study was conducted on 34 eyes of 34 keratoconus patients who had undergone PKP. Corneal hysteresis (CH), corneal resistance factor (CRF), and cornea-compensated intraocular pressure were measured at least 6 months after complete suture removal. Two groups of donor-recipient disparity (0.25 vs. 0.50 mm) were compared using the independent t test. Multivariate regression analysis was used to investigate the correlation of donor trephine size and CGT with ORA parameters. Factors influencing intraocular pressure measured with the Goldmann applanation tonometer (IOP GAT) after PKP were determined using multiple regression analysis.
  
  
  RESULTS
  Mean patient age and follow-up period were 29.6 ± 6.2 years and 82.4 ± 59.6 months, respectively. Mean CGT, CH, and CRF were 564.7 ± 36.9 μm, 10.1 ± 2.1 mm Hg, and 10.0 ± 2.3 mm Hg, respectively. CH and CRF had a significant positive correlation with donor trephine size and CGT. Significantly greater values of CH and CRF were observed in the 0.5-mm disparity group compared with the 0.25-mm disparity group. Among the studied parameters, only CH, CRF, and cornea-compensated intraocular pressure had a significant positive correlation with IOP GAT.
  
  
  CONCLUSIONS
  Graft biomechanics seem to be closer to normal values with larger grafts and greater donor-recipient disparity. These metrics had a significant correlation with IOP GAT after PKP.
authors.affiliation: Ophthalmic Research Center, Department of Ophthalmology, Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. sepehrfeizi@yahoo.com
authors.forename: Sepehr
authors.initials: S
authors.lastname: Feizi
authors.forename: Bahram
authors.initials: B
authors.lastname: Einollahi
authors.forename: Shahin
authors.initials: S
authors.lastname: Yazdani
authors.forename: Ali
authors.initials: A
authors.lastname: Hashemloo
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004548:Elasticity / Q000502:physiology; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D007640:Keratoconus / Q000503:physiopathology* / Q000601:surgery*; D015948:Keratoplasty, Penetrating; D008297:Male; D014019:Tissue Donors; D055815:Young Adult