The influence of central corneal thickness and corneal curvature radius on the intraocular pressure as measured by different tonometers: noncontact and goldmann applanation tonometers.J Glaucoma 2008; 17(8):619-25JG
The aim of this study was to examine whether or not central corneal thickness (CCT) and corneal curvature radius (CCR) influence the concordance of intraocular pressure (IOP) readings taken with a noncontact tonometer (NCT) and a Goldmann applanation tonometer (GAT).
Eighty-seven eyes from 87 patients without any histories of intraocular operation were enrolled in the present study. We calculated the difference in IOP readings between the 2 methods (NCT-GAT), and then examined the relationship between the IOP readings, and CCT and CCR using a linear regression line.
IOP measured by both NCT (r=0.515, P<0.0001) and GAT (r=0.237, P<0.05) was significantly correlated with CCT. NCT readings were significantly higher in the thicker group (CCT>or=526.9 microm) than in the thinner group (CCT<526.9 microm) (P<0.005). GAT readings had no difference between the thicker and thinner groups. IOP measured by GAT (r=-0.261, P<0.05), but not that measured by NCT (r=-0.111, P=0.3042), showed a significant negative correlation with CCR. An IOP value of (NCT-GAT) had a significant positive correlation with not only CCT (r=0.666, P<0.0001) but also CCR (r=0.227, P<0.05). The value of (NCT-GAT) was significantly higher in the thicker group than in the thinner group (P<0.005).
NCT can be more affected by CCT than GAT. CCR could influence the measurements of GAT, but not those by NCT. CCT and CCR can therefore influence the discordance of IOP readings taken with NCT and GAT.