title: Optical coherence tomography accurately measures corneal power change from laser refractive surgery.
abstract: OBJECTIVE
  To determine the ability of motion-corrected optical coherence tomography (OCT) to measure the corneal refractive power change due to LASIK.
  
  
  METHODS
  Evaluation of a diagnostic test or technology in a cohort.
  
  
  METHODS
  A total of 70 eyes from 37 subjects undergoing LASIK were measured preoperatively. A total of 39 eyes from 22 subjects were measured postoperatively and completed the study.
  
  
  METHODS
  Consecutive patients undergoing LASIK at the Duke Eye Center who consented to participate were imaged with Placido-ring topography, Scheimpflug photography, and OCT on the day of their surgery. Patients were then reimaged with the same imaging systems at the postoperative month 3 visit. Change in preoperative to postoperative corneal refractive power as measured by each of the imaging modalities was compared with the preoperative to postoperative change in manifest refraction (MRx) using the t test with generalized estimating equations.
  
  
  METHODS
  Corneal refractive power change due to LASIK as measured by Placido-ring topography, Scheimpflug photography, and OCT compared with the MRx change vertexed to the corneal plane. The change in MRx should correspond to the change in the corneal refractive power from LASIK and was considered the reference measurement.
  
  
  RESULTS
  In 22 individuals (39 eyes) returning after LASIK, we found no significant difference between the clinically measured pre- to post-LASIK change in MRx and both Scheimpflug photography (P = 0.714) and OCT (P = 0.216). In contrast, keratometry values from Placido-ring topography were found to be significantly different from the measured refractive change (P < 0.001). In addition, of the 3 imaging modalities, OCT recorded the smallest mean absolute difference from the reference measurement with the least amount of variability.
  
  
  CONCLUSIONS
  Motion-corrected OCT more accurately measures the change in corneal refractive power due to laser refractive surgery than other currently available clinical devices. By offering accurate corneal refractive power measurements in normal and surgically modified subjects, OCT offers a compelling alternative to current clinical devices for determining corneal refractive power.
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, North Carolina; Department of Ophthalmology, Duke University, Durham, North Carolina. Electronic address: ryan.mcnabb@duke.edu.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: McNabb
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, North Carolina; Department of Ophthalmology, Duke University, Durham, North Carolina.
authors.forename: Sina
authors.initials: S
authors.lastname: Farsiu
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina; Department of Biostatistics and Bioinformatics, Duke University, Durham, North Carolina.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Stinnett
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, North Carolina; Department of Ophthalmology, Duke University, Durham, North Carolina.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Izatt
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina.
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Kuo
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology; D001699:Biometry; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular / Q000502:physiology*; D041623:Tomography, Optical Coherence; D055815:Young Adult