Polar Value Analysis of Low to Moderate Astigmatism with Wavefront-Guided Sub-Bowman Keratomileusis

Abstract

Purpose To evaluate the astigmatic outcomes of wavefront-guided sub-Bowman keratomileusis (WFG-SBK) for low to moderate myopic astigmatism. Methods This study enrolled 100 right eyes from 100 patients who underwent WFG-SBK for the correction of myopia and astigmatism. The polar value method was performed with anterior and posterior corneal astigmatism measured with Scheimpflug camera combined with Placido corneal topography (Sirius, CSO) and refractive astigmatism preoperatively and 1 month, 3 months, and 6 months postoperatively. Results Similar results for surgically induced astigmatism (SIA) and error of the procedure in both anterior corneal astigmatism (ACA) and total ocular astigmatism (TOA). There was a minor undercorrection of the cylinder in both ACA and TOA. Posterior corneal astigmatism (PCA) showed no significant change. Conclusions Wavefront-guided SBK could provide good astigmatic outcomes for the correction of low to moderate myopic astigmatism. The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after WFG-SBK for myopic astigmatism. Polar value analysis can be used to guide adjustments to the treatment cylinder alongside a nomogram designed to optimize postoperative astigmatic outcomes in myopic WFG-SBK.

Femtosecond LASIK for the correction of low and high myopic astigmatism

“…It is generally agreed that the surgical correction of moderate to high astigmatism is less predictable than the correction of spherical errors [13][14][15]. The suboptimal results with high astigmatism may be due to the imprecise alignment of the elliptic ablation axis, the under-compensated cyclotorsion and the unaccounted coupling effect that toric ablation can have on spherical error [16].…”

Polar value analysis of astigmatic change and rotational stability after implantation of V4c toric implantable collamer lens

“…Therefore, it is necessary to analyze the causes of residual astigmatism after implantation of the V4c TICL. Astigmatic power is expressed as magnitude in diopters and direction in degrees (10)(11)(12)(13)(14)(15)18,19). Therefore, vector analysis should be used to evaluate the effect of the V4c TICL on astigmatic correction.…”