A Comparison Study Between Four Different Pachymeters to Measure Corneal Thickness

INTRODUCTION: To compare the correlation and agreement between the central corneal thickness (CCT) measurements with ultrasound pachymeter and three different non-contact pachymeters and to analyze their influence on intraocular pressure (IOP) measurements.
METHODS: This prospective study included 102 healthy adults. Optical biometer (OB), scheimpflug corneal topographer (TOPO), non-contact pachytonometer (NCP), and ultrasound pachymeter (UP) were carried out to measure the corneal thickness. Pearson and Spearman correlation and a 95% limit of agreement were calculated.
RESULTS: In this prospective study, the CCT of 102 right eyes of 102 healthy volunteers were analyzed. CCT measured with optic biometer, corneal topography, ultrasound pachymeter and non-contact pachytonometer were 534.7 (438-629), 544.8 (444-634), 553.1 (449-674) and 562.9 (464-665 µm), respectively. There were strong correlations between all pachymeters by Pearson correlation analysis. The correlation of Pearson between all measurement methods were over 0.950. When the CCT was divided into the three groups according to corneal thickness ranges, the correlation was higher than 0.7 in all groups (r=0.72-0.91 for <510 µm, r=0.85-0.95 for 510-580 µm, r=0.82-0.93 for >580 µm) by Spearman correlation analysis. A significant positive correlation was observed between the IOP values and CCT obtained by all pachymeters with a trend toward increasing the IOP with increasing corneal thickness.
DISCUSSION AND CONCLUSION: The correlations between the pachymeters were high in normal corneal thickness, whereas it was slightly lower in the thick and thin cornea. A significant positive correlation was observed between IOP and CCT in all pachymeters.