Accuracy of IOP measurements questioned

Dynamic contour tonometry (DCT) may be more accurate than Goldmann applanation tonometry (GAT) in measuring intraocular pressure (IOP), according to study results published in the February issue of Eye.

Pierre Ceruti of the Borgo Trento Hospital at the University of Verona, Italy and colleagues used DCT and GAT to measure IOP in healthy eyes (n=100), eyes with primary open angle glaucoma (n=100) and eyes with primary angle closure glaucoma (n=100). The team also noted the age of patients, measured corneal thickness (CCT) and curvature (CC), and axial length (AL), and then conducted regression analysis to evaluate the impact these metrics exerted on each of the measurement techniques.

The IOP values measured by DCT were 2.6±1.9 mmHg higher when compared with GAT measurements, and the degree of difference increased proportionally with CCT. With both increasing CCT and IOP, however, the degree of difference between the measurements reduced. DCT measurements were not affected by CCT, although GAT measurements were. CC, AL and age did not impact on readings with either instrument.

The team concluded that the degree of difference in measurement was higher in healthy eyes than in glaucomatous eyes; overall, GAT measurements were more affected by CCT and measured lower IOP readings when compared with DCT.