ESCRS - FP11.14 - Impact Of Eye-Tracking-Assisted Centration Versus Manual Alignment Of The Treatment Zone Centration After Klex (Smile): A Prospective Randomized Double-Blinded Contralateral Eye Study

Impact Of Eye-Tracking-Assisted Centration Versus Manual Alignment Of The Treatment Zone Centration After Klex (Smile): A Prospective Randomized Double-Blinded Contralateral Eye Study

Published 2026 - 44th Congress of the ESCRS

Reference: FP11.14 | Type: Free paper | DOI: 10.82333/w8t7-rj71

Authors: Dr Anke Messerschmidt-Roth 1 , A/Prof. Walter Sekundo* 1 , Mrs Aleandra Stein 1 , Mr Karsten Pfeiffer 1 , Mr Richard Heinrich Johannes Lorenz 2

1Department of Ophthalmology,Philipps-University,Marburg,Germany, 2Philipps-University,Marburg,Germany

Purpose

A perfect centration of the treatment zone is a key determinant of visual quality in corneal refractive surgery. While excimer laser systems implement active eye tracking, the second-generation femtosecond laser (VisuMax 500, Carl Zeiss Meditec AG/Germany) used in SMILE procedure relied on manual centration. This study evaluates whether centration assistance systems with the newest technology (CentraLign/OcuLign; VisuMax 800, Carl Zeiss Meditec AG/Germany) alters the accuracy of treatment zone positioning compared to the manual alignment.

Setting

Department of Ophthalmology, Philipps University of Marburg, Germany

Methods

In this prospective, randomized, controlled, double-blinded single-center study, patients undergoing bilateral SMILE Pro surgery were included. One eye received assisted centration, while the fellow eye was centered on the 1st Purkinje reflex. Preoperative pupil center deviation measured by the IOLMaster700 was entered into the laser software to optimize centration. Pre- and postoperative assessments included corneal tomography, wavefront analysis, manifest refraction, and corrected and uncorrected distance visual acuity. The distance between the point of maximum pachymetric difference and the visual axis was calculated using tomography. Normality was tested with the Shapiro–Wilk test; paired t-test was applied (p<0.05).

Results

One single experienced surgeon treated 92 eyes of 46 patients. The data in both groups was normally distributed. In the centration assisted group mean decentration was 0.387 ± 0.228 mm, ranging from 0.057 to 1.062 mm. In contrast, in the manual alignment group mean decentration was 0.449 ± 0.216 mm, ranging from 0.15 to 1.034 mm.
Paired t-test analysis demonstrated a statistically significant difference regarding the decentration of the treatment zone, with the decentration being more pronounced in the manual alignment group (P<0,05).

Conclusions

Assisted centration of the 3rd generation laser platform improves the accuracy of treatment zone centration in SMILE Pro compared to manual alignment. The findings support the routine use of active centration systems in SMILE Pro.