Comparison of Pascal Dynamic Contour Tonometer, Reichart Ocular Response Analyzer and Goldmann Applanation Tonometer in Eyes After Penetrating Keratoplasty

A few tonometers are used today in clinical practice for measuring intra ocular pressure (IOP). Each tonometer is based on different technology.

Post penetrating keratoplasty (PK) eyes are at risk for developing secondary glaucoma (9-14%). Elevation of the IOP may cause rejection of the graft or alternately a loss in the endothelial cell layer count causing decompensation of the cornea. Therefore, measuring accurately the IOP in this population is of great importance.

Measuring IOP in post PK is not an easy challenge, mainly because of parameters like the central corneal thickness (CCT), the curvature of the cornea, the axial length and biomechanical properties which diverse from normal eyes.

The Goldmann applanation tonometer (GAT) is the gold standard tonometer for measuring IOP and is the most popular tonometer clinically used. IOP measurements via the GAT are based on the assumption that the CCT is constant. post PK eyes CCT might diverse from normal eyes causing GAT IOP measurements to be inaccurate. The Pascal dynamic contour tonometer (DCT) measures IOP independently of corneal parameters. The Ocular response analyzer (ORA) is based on a non contact technique of measurement. The tonometer is thought to be independent of factors such as CCT.

The aim of the study is to compare intraocular pressure (IOP) measured by the Reichert Ocular Response Analyzer (ORA), Pascal dynamic contour tonometer (DCT) and Goldmann applanation tonometer (GAT) in eyes after Penetrating Keratoplasty (KPL). In addition its aim is to discover the dependence of different parameters, like - CCT, curvature of the cornea, axial length and biomechanical properties on IOP measurement to elucidate the appropriate tonometer for this population.