Centralign Software Validation: Achieveing Optimal Visual Axis Centration With Visumax 800

To validate the accuracy of the CentraLign software which is the centration guide that allows the surgeon to centre the treatment on the visual axis in myopic eyes treated with small incision lenticule extraction (SMILE) using Visumax 800 (Carl Zeiss Meditec AG).

A retrospective analysis of patients enrolled in a post-market, multicentre investigation conducted at Nethradhama Superspeciality Eye Hospital, Bangalore.

  The study involved 114 consecutive eyes that underwent Small Incision Lenticule Extraction (SMILE) using the CentraLign centration software integrated with the VisuMax 800 femtosecond laser platform. To assess the lenticule extraction parameters, a difference map was created by comparing preoperative and 6-month postoperative tangential curvature maps from the ATLAS 9000 corneal topographer (Carl Zeiss Meditec AG). A fixed grid was placed over the difference map to locate the geometric centre of the extracted lenticule. This was then compared to the preoperative visual axis, and the offset between the lenticule centre and the visual axis was measured and quantified.

 The mean difference between the Visual Axis X-coordinate (VAXC) and the Centre of Lenticule X-coordinate (CLXC) was -0.05325, with a t-value of -1.881 (df = 113) and a two-tailed p-value of 0.063 (>0.05). This suggests a statistically significant decentration of the lenticule along the horizontal axis. On the other hand, the mean difference between the Visual Axis Y-coordinate (VAYC) and the Centre of Lenticule Y-coordinate (CLYC) was 0.08623, with a t-value of 3.330 (df = 113) and a two-tailed p-value of 0.001 (<0.05), indicating no statistically significant decentration of the lenticule along the vertical axis.

The mean difference in the X and Y coordinates remains well within 100 microns, showcasing the effectiveness of the CentraLign software in achieving centration. The significant decentration in the X coordinates is mainly attributed to the surgeon's technique in aligning the centre between the pupillary axis and the visual axis.