title: Influence of different keratoplasty techniques on the biomechanical properties of the cornea.
abstract: OBJECTIVE
  To evaluate and compare corneal biomechanical changes after deep anterior lamellar keratoplasty (DALK) versus penetrating keratoplasty (PK) using the ocular response analyzer (ORA).
  
  
  METHODS
  This prospective comparative study included 65 eyes (65 patients). Patients were divided into three groups: DALK (20 eyes), PK (25 eyes) and control group of normal subjects (20 eyes). Ocular response analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure and cornea-compensated intraocular pressure at 6 and 12 months postoperatively. Central corneal thickness (CCT) was measured using ultrasonic pachymetry.
  
  
  RESULTS
  Both mean CH and mean CRF were significantly lower in PK group (sutures on; 10.1 ± 1.11 and 9.6 ± 1.08 mmHg) than in DALK (sutures out; 12.25± 1.13 and 12.09 ± 1.05 mmHg) and control groups (12.98 ± 1.19 and 12.59 ± 0.94 mmHg) at 6 months, respectively (p <0.0001). After 1 year, there was no statistically significant difference in mean CH and CRF between DALK (12.68 ± 1.11 and 12.18 ± 1.11 mmHg) and PK groups (still sutures on; 12.36 ± 1.32 mmHg, p = 0.39 and 11.83 ± 1.26 mmHg, p = 0.33, respectively); however, the mean CRF was significantly lower in the PK than the control group (p = 0.03). No statistically significant difference in mean CH or mean CRF was found between DALK and control groups at any time-point.
  
  
  CONCLUSIONS
  Compared with PK, DALK provides rapid return of normal corneal biomechanics, perhaps because of the combined healing at both the deep interface and graft margin, shorter period of steroid treatment and the intactness of Descemet membrane in these eyes.
authors.affiliation: Department of Ophthalmology, Faculty of medicine, Al-Azhar University, Cairo, Egypt.
authors.forename: Almamoun
authors.initials: A
authors.lastname: Abdelkader
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003315:Cornea / Q000502:physiology*; D003316:Corneal Diseases / Q000503:physiopathology / Q000601:surgery*; D063171:Corneal Pachymetry; D016039:Corneal Transplantation; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
keywords: corneal biomechanics; corneal hysteresis; corneal resistance factor; deep anterior lamellar keratoplasty; ocular response analyzer; penetrating keratoplasty