Central Corneal Thickness Measurements Exhibit Variability Between Devices

While strong agreement exists among various devices used to measure central corneal thickness (CCT), their values differ significantly in children and should not be used interchangeably in clinical practice, according to a study published in Photodiagnosis and Photodynamic Therapy. 

Researchers enrolled 83 healthy children (50 girls; mean age, 11.1±2.8 years) in a retrospective cross-sectional study. The CCT was measured using a Scheimpflug-Placido disk system, specular microscopy, non-contact tono-pachymetry, and optical low-coherence reflectometry. The agreement rates between the devices were analyzed using intraclass correlation coefficient (ICC) values with two-way mixed model and Bland-Altman plots. 

Overall, mean CCT values obtained using the Scheimpflug-Placido disk system, specular microscopy, non-contact tono-pachymetry, and optical low-coherence reflectometry were 555.9±37 μm, 553.5±39 μm, 569.3±33 μm, and 559.7±38 μm, respectively. 

Agreement between the non-contact tono-pachymetry device and the Scheimpflug-Placido disk system, optical low-coherence reflectometry, and specular microscopy was 0.875, 0.903, and 0.842, respectively. Agreement was 0.979 between the Scheimpflug-Placido disk system and optical low-coherence tomography, 0.978 between the Scheimpflug-Placido disk system and specular microscopy, and 0.969 between optical low-coherence reflectometry and specular microscopy.

Despite statistically strong agreement between some of the devices, investigators urge clinicians to consistently use a single device to obtain CCT measurements. 

“[B]ecause there were statistically significant differences among the CCT measurements of these four devices, we concluded that they could not be used interchangeably,” according to the researchers. “These differences might result from the different optical structures of the devices.”

Study limitations include a retrospective nature and single center design.