Influence of design parameters on peripheral defocus after keratorefractive lenticule extraction

This study investigated changes in peripheral defocus before and after keratorefractive lenticule extraction (KLEx) and examined the associations between surgical design parameters and changes in peripheral defocus. This prospective longitudinal pre-post study included 78 patients with myopia who voluntarily chose to undergo KLEx from March to July 2023 at the Optometry Center of Tianjin Eye Hospital, Tianjin Medical University, Tianjin, China. Patients were divided into three groups according to spherical equivalent refractive error. Retinal relative defocus values (RDVs) within the 0°-53° field were measured using multispectral refractive topography before surgery and 3 months postoperatively. Paired-sample t-tests were used to compare preoperative and postoperative changes. Associations between surgical parameters and changes in RDVs were analyzed using Pearson's correlation analysis. Three months after KLEx, myopic defocus increased at 10°-20°, the RDV at 20°-30° shifted from hyperopic to myopic defocus, and hyperopic defocus decreased at 30°-40° and 40°-53°. Central corneal cutting thickness was positively correlated with the change in RDV at 40°-53°. Percent tissue altered (PTA) was positively correlated with changes in RDVs at 30°-40° and 40-53°. Peripheral hyperopic defocus was reduced after KLEx. Central corneal cutting thickness appears to be an important factor associated with changes in peripheral defocus after KLEx. Greater corneal cutting thickness during surgery was associated with a greater postoperative reduction in peripheral hyperopic defocus.