title: Central corneal thickness determination in corneal edema using ultrasound pachymetry, a Scheimpflug camera, and anterior segment OCT.
abstract: OBJECTIVE
  The purpose of this study is to determine the influence of post-surgical corneal edema on the reliability and reproducibility of central corneal thickness (CCT) measurements by a Scheimpflug camera (Pentacam), ultrasound pachymetry (USP), and anterior-segment spectral-domain optical coherence tomography (AS-OCT).
  
  
  METHODS
  Thirty-two patients planned for cataract surgery (n = 16) or vitrectomy (n =  6) were included in a prospective study. The non-surgery eye was used as control. Two investigators acquired two measurements each, with the Pentacam (Oculus, Germany) and the AS-OCT (Heidelberg Engineering, Germany) in a randomized order, followed by USP (Tomey SP-100, Germany). CCT was evaluated using the apex value for Pentacam, the corneal apex cut in AS-OCT and averaging eight single measurements for USP. Coefficients of variation (COV) and intra-class correlation coefficients (ICC) were determined.
  
  
  RESULTS
  Post-surgery corneas showed a thickness of (investigators 1 and 2): Pentacam (615.9 ± 58.02 μm and 615.1 ± 60.17 μm), USP (601.4 ± 63.77 μm and 614.5 ± 70.91 μm), AS-OCT (608.8 ± 65.67 μm and 606.9 ± 64.41 μm) ,with no significant difference (ANOVA p > 0.99). The COVs (investigators 1 and 2) for control eyes were: Pentacam (0.78 ± 0.52 and 0.70 ± 0.76), USP (0.66 ± 0.29 and 0.98 ± 0.44), AS-OCT (0.59 ± 0.61 and 0.59 ± 0.40). The COVs (investigators 1 and 2) for post-surgical eyes were: Pentacam (0.98 ± 1.25 and 0.97 ± 0.73), USP (0.73 ± 0.64 and 1.35 ± 0.85), AS-OCT (1.34 ± 1.57 and 1.19 ± 1.18).The ICC was determined in post-surgery corneas (ICC > 0.96) and control corneas (ICC > 0.95).
  
  
  CONCLUSIONS
  USP measurements have the highest user dependence. Post-surgical corneal edema leads to higher intraobserver variability. All methods reached a high level of agreement in CCT determination in edematous as well as healthy corneas.
authors.affiliation: Department of Ophthalmology, RWTH Aachen University, Pauwelsstr. 30, 52074, Aachen, Germany, dkuerten@ukaachen.de.
authors.forename: David
authors.initials: D
authors.lastname: Kuerten
authors.forename: Niklas
authors.initials: N
authors.lastname: Plange
authors.forename: Eva Charlotte
authors.initials: EC
authors.lastname: Koch
authors.forename: Antonis
authors.initials: A
authors.lastname: Koutsonas
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
authors.forename: Matthias
authors.initials: M
authors.lastname: Fuest
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002387:Cataract Extraction; D003315:Cornea / Q000473:pathology*; D015715:Corneal Edema / Q000175:diagnosis* / Q000209:etiology; D063171:Corneal Pachymetry; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009929:Organ Size; D010781:Photography; D011183:Postoperative Complications; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence; D014821:Vitrectomy