Validation Of Centralign Software On The Visumax 800 For Laser Pattern Centration On The Visual Axis

To validate the accuracy of the CentaLign 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).

It is a restrospective analysis of patients enrolled in post market multicentric study conducted at Nethradhama Superspeciality Eye Hospital, Bangalore.

This study included 114 consecutive eyes treated with SMILE with the CentraLign centration software in VisuMax 800 femtosecond laser. A difference map of the pre operative and 6^th month post operative tangential curvature map was obtained using the ATLAS 500 (Carl Zeiss Meditec AG) to mark the area of lenticule extraction. A fixed grid was superimposed on the difference map to locate the centre of the lenticule. This was compared with the pre op visual axis and the offset from the centre of lenticule was measured.

The mean difference between the Visual Axis X Co-ordinate (VAXC) and the Centre of Lenticule X Co-ordinate (CLXC)  is -0.05325. The t₍₁₁₃₎ = -1.881with p-value(two tailed) is 0.063 (>0.05), and this is evidence to prove that there was significant decentration of the lenticule along horizontal axis. The mean difference between the Visual Axis Y Co-ordinate (VAYC) and Centre of Lenticule Y Co-ordinate (CLYC) is 0.08623. The t₍₁₁₃₎ = 3.330 with p-value(two tailed) is 0.001 (< 0.05), hence there was no significant decentration of the lenticle along vertical axis.

The mean difference of the X and Y coordinates are within 100micros which validates the centration of the centraLign software. The significant decentration of the X coordinates can be attributed to the surgeons method of aligning the centre between the pupillary axis and the visual axis.