Distance of Corneal Vertex and Effective Optical Zone Margin Following Keratorefractive Lenticule Extraction in Myopic Astigmatism

To determine the distances from the corneal vertex to the effective optical zone margin along its major (DVOx) and minor axes (DVOy), to evaluate their correlation with corneal wavefront aberrations after keratorefractive lenticule extraction (KLEx) in myopic astigmatism, and to identify potential factors related to DVOx and DVOy. This study included 93 eyes of 51 patients who underwent KLEx with myopic astigmatism. The decentration, area of effective optical zone and the DVOx and DVOy on tangential topography difference map were measured. Induced corneal aberrations were obtained before and six months after surgery. Piecewise regression analysis was used to determine the relationship between the magnitudes of DVOx and DVOy and induced corneal aberrations. The Pearson correlation test was used to identify potential factors related to DVOx and DVOy. The mean DVOx was 2.68 ± 0.24 mm, and the mean DVOy was 2.31 ± 0.22 mm. The Pearson correlation coefficients were higher for induced horizontal and vertical coma, coma, trefoil, higher-order aberrations with DVO, compared to those with decentration or area alone. The DVOx and DVOy were inversely correlated with the correction of sphere, spherical equivalent, and percent tissue altered. Subgroup analysis revealed that induced corneal aberrations were significantly greater in subgroups with DVOx < 2.316 mm and DVOy < 2.183 mm, except for trefoil. By integrating both EOZ area and decentration, DVOx and DVOy provide a more comprehensive assessment of surgically induced corneal aberrations in KLEx surgery, establishing them as crucial evaluation parameters for optimizing surgical planning and enhancing visual outcomes by identifying potential causes of suboptimal results. DVO exhibited a stronger association with corneal aberrations in KLEx surgery, compared to either decentration or area. DVOx and DVOy can serve as new evaluation parameters to optimize customized surgical plan and enhance visual outcomes.