Comparison of Treatment Zone Decentration Between VISUMAX 500 and VISUMAX 800 Keratorefractive Lenticule Extraction Using Anterior Segment Optical Coherence Tomography

Background/Objectives: To compare treatment-zone decentration after small-incision lenticule extraction (SMILE) performed with VISUMAX 500 and VISUMAX 800 using corneal thickness difference maps derived from anterior segment optical coherence tomography.

Methods

This retrospective comparative study included 44 eyes of 22 participants who underwent SMILE with VISUMAX 500 or VISUMAX 800 by a single surgeon and had preoperative and 3-month postoperative CASIA2 examinations. Treatment-zone centers were primarily identified manually relative to the corneal vertex. Between-platform differences were analyzed using generalized estimating equations (GEE) accounting for inter-eye correlation, with additional adjustment for preoperative cylinder. Participant-level analyses and semi-automated radial color-symmetry localization were performed as sensitivity analyses.