*Correspondence - Mustafa Yusuf: mustafayusuf@nhs.net

Objective Corneal topography is a crucial part of the decision making process in clinics throughout the country. numerous machines are available, therefore it is important if a patient has topography performed on one device it produces consistent results on another device. Our service is somewhat unique with eye clinics running on two different sites with two different topography machines. This study aims to compare the commonly used Galilei machine with the newer Anterion machine to see if the measurements are comparable.

Methods and Analysis We identified 20 patients (between the ages of 15 and 40) with a diagnosis of keratoconus who had undergone both Galilei and Anterion topography. Only those patients who had undergone both scans within a 2-week time frame (and should therefore have very similar topography readings) were included. We compared Flat Sim K, Steep Sim K, K Max and Pachymetry readings between the two devices.

Results The mean difference in Flat Sim K was 0.41. The largest difference was 1.1. The mean difference in Steep Sim K was 0.52. The largest difference 1.8. The mean difference in K Max was 0.73. The largest difference 2.1. The mean difference in pachymetry was 11 µm. The largest difference 21 µm.

Conclusion There was considerable differences in measurements between the two devices, with K Max and Pachymetry showing the most disparity. We therefore recommend caution when deciding upon, for example keratoconus progression, in a patient who has undergone topography on two different devices.