Central corneal thickness measurements with partial coherence interferometry, ultrasound, and the Orbscan system.
OBJECTIVE
To compare the reliability of central corneal thickness measurements (CCT) obtained with partial coherence interferometry (PCI), ultrasound pachymetry, and the Orbscan system.


METHODS
Cross-sectional study.


METHODS
Twenty healthy subjects with CCT measurements in both eyes.


METHODS
The CCT measurements were obtained with PCI, ultrasound pachymetry, and the Orbscan system. In each eye, 2 investigators performed 5 repeated measurements with each pachymetric device. Intraclass correlation coefficients (kappa) were calculated and mean CCT measurements were compared.


METHODS
The CCT measurements obtained with ultrasound pachymetry, the Orbscan system (Orbtek Inc., Salt Lake City, UT), and PCI.


RESULTS
Mean CCT values measured with ultrasound pachymetry were significantly thicker than those measured with PCI (21.5 microm; P<0.001) or the Orbscan system (19.8 microm; P<0.001). The correlation coefficients for the intraobserver variability were 0.999 for PCI measurements, 0.983 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. The correlation coefficients for the interobserver variability were 0.998 for PCI measurements, 0.980 for ultrasound pachymetry measurements, and 0.988 for Orbscan system measurements. There was a slightly better consistency between ultrasound pachymetry and PCI (kappa = 0.96) than between the Orbscan system and PCI (kappa = 0.92) and between ultrasound pachymetry and the Orbscan system (kappa = 0.89).


CONCLUSIONS
Partial coherence interferometry was the method with the least intraobserver or interobserver variability. Mean CCT as measured with ultrasound pachymetry was approximately 20 microm thicker than with the Orbscan system and PCI. However, corneal thickness measurements with ultrasound pachymetry and PCI were slightly more consistent than those of the Orbscan system and PCI. This slightly better consistency, however, may be important, especially in corneal refractive surgery.
Rainer
Georg
G
Department of Ophthalmology, University of Vienna, Vienna, Austria. georg.rainer@akh-wien.ac.at
Findl
Oliver
O
Petternel
Vanessa
V
Kiss
Barbara
B
Drexler
Wolfgang
W
Skorpik
Christian
C
Georgopoulos
Michael
M
Schmetterer
Leopold
L
D000328:Adult; D019412:Anatomy, Cross-Sectional; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007368:Interferometry / Q000379:methods; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D014463:Ultrasonography