Effects of central corneal thickness, central corneal power, and axial length on intraocular pressure measurement assessed with goldmann applanation tonometry

Abstract

Purpose: To determine the effects of central corneal thickness (CCT), central corneal power (CCP), and axial length (AL) on the measurement of intraocular pressure (IOP) using Goldmann applanation tonometry, and the effects of CCP and AL on CCT.

Methods: Charts of 147 consecutive patients undergoing preoperative examinations for cataract surgery between April 2006 and April 2007 in our clinic were reviewed retrospectively. CCT, CCP, and AL were measured by ultrasonic pachymeter (Micropach Model 200P, Sonomed, Lake Success, N.Y. USA), autorefractokeratometer (KR 8800, Topcon, Tokyo, Japan), and ultrasound biometry (EZ Scan AB 5500+ Sonomed, Lake Success, N.Y. USA). Pearson correlation analysis and multiple linear regression analysis were used as indicated, and only one eye of each subject was included in the statistical analysis.

Results: Ninety-eight eyes of 98 patients were included in the study. IOP and CCT were significantly and positively correlated (P<0.001), and CCT and CCP (P=0.001) were inversely correlated. Multiple regression analysis showed that the effect of CCT on IOP was statistically significant (P<0.001), but the effects of CCP and AL on IOP were not significant (P=0.614, P=0.831, respectively). IOP increased by 0.29 mmHg for each 10 microm increase in CCT.

Conclusions: CCT, but not CCP or AL, significantly affected IOP readings obtained by Goldmann applanation tonometry. The effect of CCP on IOP was weak and not significant despite the significant inverse correlation between CCT and CCP.