title: Comparison of optical low-coherence reflectometry and ultrasound pachymetry in measuring corneal graft thickness.
abstract: OBJECTIVE
  To compare optical low-coherence reflectometry (OLCR) and ultrasound pachymetry in measuring corneal graft thickness in patients after keratoplasty.
  
  
  METHODS
  We retrospectively measured the central graft thickness in 41 eyes of 41 patients with the OLCR pachymeter (Haag Streit, Koeniz, Switzerland) and the SP-2000 contact ultrasound pachymeter (Tomey, Nagoya, Japan). Five separate measurements were performed on each eye with both methods. Mean, SD, repeatability, and coefficient of variation of measurements were calculated, and the correlation between the 2 methods was studied with Spearman regression.
  
  
  RESULTS
  Mean central graft thickness was 546 +/- 51 (SD) microm with the contact ultrasound pachymeter and 546 +/- 47 microm with the OLCR pachymeter. The correlation between both methods was strong (rs = 0.96). No significant differences in mean SD of measurements were observed between OLCR pachymetry (mean SD = 4.66 microm) and contact ultrasound pachymetry (mean SD = 4.88 microm). The repeatability of both methods was comparable (P = 0.06) and high (the average coefficient of variation of the central corneal graft thickness was 0.9% with both pachymeters). The postoperative time did not affect the correlation between both pachymeters (P > 0.05).
  
  
  CONCLUSIONS
  Central corneal graft thickness values obtained with the OLCR pachymeter were similar to those obtained with a contact ultrasound pachymeter. In some cases of lamellar keratoplasty, the corneal refractive index could change at the interface level that could affect OLCR measurements.
authors.affiliation: Department of Ophthalmology, Centre Hospitalier National d'Ophtalmologie des XV-XX, Université Pierre et Marie Curie Paris 6, Paris, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaujoux
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Borderie
authors.forename: Hakim
authors.initials: H
authors.lastname: Yousfi
authors.forename: Tristan
authors.initials: T
authors.lastname: Bourcier
authors.forename: Olivier
authors.initials: O
authors.lastname: Touzeau
authors.forename: Laurent
authors.initials: L
authors.lastname: Laroche
mesh_terms: D001837:Body Weights and Measures; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology*; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000000981:diagnostic imaging / Q000473:pathology*; D011184:Postoperative Period; D015203:Reproducibility of Results; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*; D014463:Ultrasonography