Testing the tonometers

Intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT) and the TonoPen appear to be influenced by central corneal thickness (CCT), according to a study published in the May issue of Acta Ophthalmologica Scandinavica.

A team of researchers led by Maria Salvetat of Santa Maria della Misericordia Hospital in Udine, Italy, compared IOP measurements taken with the Pascal DCT, TonoPen and Goldman applanation tonometry (GAT).

One eye in 101 consecutive primary open-angle glaucoma patients underwent ultrasonic CCT measurement and IOP evaluation with all three systems, in random order.

After assessing the agreement between results using the Bland-Altman method, the authors concluded that the agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings. Pascal DCT, however, was found to significantly overestimate IOP values compared with GAT and both Pascal DCT and the TonoPen were influenced by CCT, the influence being greater for the latter.