title: Central Corneal Thickness Reproducibility among Ten Different Instruments.
abstract: To assess agreement between one ultrasonic (US) and nine optical instruments for the measurement of central corneal thickness (CCT), and to evaluate intra- and inter-operator reproducibility.
  
  
  
  In this observational cross-sectional study, two masked operators measured CCT thickness twice in 28 healthy eyes. We used seven spectral-domain optical coherence tomography (SD-OCT) devices, one time-domain OCT, one Scheimpflug camera, and one US-based instrument. Inter- and intra-operator reproducibility was evaluated by intraclass correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman test analysis. Instrument-to-instrument reproducibility was determined by ANOVA for repeated measurements. We also tested how the devices disagreed regarding systemic bias and random error using a structural equation model.
  
  
  
  Mean CCT of all instruments ranged from 536 ± 42 μm to 577 ± 40 μm. An instrument-to-instrument correlation test showed high values among the 10 investigated devices (correlation coefficient range 0.852-0.995; p values <0.0001 in all cases). The highest correlation coefficient values were registered between 3D OCT-2000 Topcon-Spectral OCT/SLO Opko (0.995) and Cirrus HD-OCT Zeiss-RS-3000 Nidek (0.995), whereas the lowest were seen between SS-1000 CASIA and Spectral OCT/SLO Opko (0.852). ICC and CV showed excellent inter- and intra-operator reproducibility for all optic-based devices, except for the US-based device. Bland-Altman analysis demonstrated low mean biases between operators.
  
  
  
  Despite highlighting good intra- and inter-operator reproducibility, we found that a scale bias between instruments might interfere with thorough CCT monitoring. We suggest that optimal monitoring is achieved with the same operator and the same device.
authors: *MD †PhD Department of Ophthalmology, Vita-Salute University, San Raffaele Scientific Institute, Milan, Italy (LP, LI, MG, FB); Vita-Salute San Raffaele University, Milan, Italy (AA); and Cornea and Ocular Surface Unit, San Raffaele Scientific Institute, Milan, Italy (PR).
authors: Luisa
authors: L
authors: Pierro
authors: Lorenzo
authors: L
authors: Iuliano
authors: Marco
authors: M
authors: Gagliardi
authors: Alessandro
authors: A
authors: Ambrosi
authors: Paolo
authors: P
authors: Rama
authors: Francesco
authors: F
authors: Bandello
mesh_terms: D000328:Adult; D003315:Cornea / Q000033:anatomy & histology*; D063171:Corneal Pachymetry / Q000295:instrumentation; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D019721:Ophthalmoscopes; D009929:Organ Size; D010781:Photography / Q000295:instrumentation; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000295:instrumentation