title: Comparison of corneal thickness measured with optical coherence tomography, ultrasonic pachymetry, and a scanning slit method.
abstract: OBJECTIVE
  To investigate the relationship between 1310-nm optical coherence tomography (OCT), an ultrasound pachymeter, and the Orbscan II (Bausch & Lomb, Rochester, NY) in corneal thickness measurements before and after LASIK.
  
  
  METHODS
  Twenty-eight eyes of 14 patients with a mean age of 39.9 +/- 8.6 years underwent LASIK for correction of myopia with or without astigmatism. Central corneal thickness was measured with real-time 1310-nm OCT and Orbscan preoperatively and 1 day, 1 week, and 1 month postoperatively, and with an ultrasound pachymeter preoperatively and 1 month postoperatively.
  
  
  RESULTS
  Measurements of corneal thickness by all instruments correlated well with one another pre- and postoperatively (r value range: 0.87 to 0.94, P<.05); however, there were significant differences among these methods (ANOVA: P<.005). Baseline readings for ultrasound and Orbscan were similar, as were readings 1 month postoperatively for OCT and Orbscan (P>.05). Thickness measured by OCT was thinner than for other instruments preoperatively (P<.005) and thicker than Orbscan postoperatively (P<.005). Significant corneal thinning (P<.001) was found with all study devices 1 day after laser ablation. Significant corneal thinning (P<.005) was found with OCT and Orbscan 1 week compared to 1 day postoperatively, and thickening (post hoc: P<.001) was evident at 1 month compared to 1 week postoperatively.
  
  
  CONCLUSIONS
  Although the instruments correlated well in measuring corneal thickness after LASIK, there were significant differences. All instruments indicated corneal swelling and recovery during the first postoperative week and thickening at 1 month.
authors.affiliation: Department of Ophthalmology, Case Western Reserve University/University Hospitals of Cleveland, Cleveland, Ohio, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Thomas
authors.forename: Jianhua
authors.initials: J
authors.lastname: Wang
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Rollins
authors.forename: Julie
authors.initials: J
authors.lastname: Sturm
mesh_terms: D000328:Adult; D000886:Anthropometry / Q000379:methods*; D001251:Astigmatism / Q000601:surgery; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D009216:Myopia / Q000601:surgery; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D014465:Ultrasonics; D014463:Ultrasonography