Corneal dioptric power and astigmatism: A comparison between colour light-emitting diode based (Cassini^TM) and...

To determine the agreement and to compare the measurements obtained from a colour light-emitting diode based (Cassini^TM) and Scheimpflug (Pentacam^TM) based topography in the evaluation of the anterior, posterior, and total corneal power and astigmatism.

A total of 30 eyes from 30 healthy patients were consecutively measured using Pentacam^TM and Cassini^TM. The main evaluated parameters were the anterior, posterior, and total dioptric power, and a power vector analysis of the astigmatism. The agreement between both devices was analysed using the intraclass correlation coefficient (ICC) and performing Bland-Altman plots. The comparison of means was performed using paired Student t-test.

The agreement between both devices when comparing the anterior and total corneal dioptric power was very high (ICC>0.85), but not when studying the posterior cornea (ICC<0.5). In the astigmatism analysis, measurements from the anterior cornea also showed an excellent agreement (ICC>0.78), but was poor for the corneal posterior surface (ICC<0.31). When studying the corneal dioptric power, no statistically significant differences were found for the anterior surface (P>.05), but Pentacam^TM obtained higher values for posterior and total surfaces (P<.001). As regards the magnitude of the astigmatism, no significant differences were found between both devices.

Both devices were highly comparable when studying the anterior cornea, but the agreement was poor-moderate when measuring posterior cornea. Therefore, the data obtained by both topographers are not interchangeable.