Astigmatism Correction Through Excimer Laser Ablation Profiles: A Descriptive Review and Guide.

PURPOSE: To review the reported outcomes for correction of astigmatism using excimer laser-based corneal refractive surgery techniques and to present distinctly the intricacies of the different ablation profiles.

METHODS

Keywords such as "refractive correction," "excimer lasers," "ablation profiles," and "astigmatism" were used for literature research. Inclusion criteria were strict relevance and adequacy to the clinical questions under research, and availability of the abstract in the English language.

RESULTS

Bitoric, cross-cylinder, and custom wavefront-optimized (aberration-neutral) or wavefront-guided treatments are used in modern laser systems to correct astigmatism. From scientific literature reviewed in this article, laser ablation to correct astigmatism was found to produce satisfactory visual outcomes in terms of safety, efficacy, and predictability. Custom ablation respecting postoperative corneal curvature gradient, correcting true corneal astigmatism after eliminating the higher order aberrations, and accurately compensating for possible cyclotorsion will result in patient satisfaction.

CONCLUSIONS

Integrating subjective and objective assessment of astigmatism effectively to optimize treatment outcomes is complex, particularly across a wide range of refractive errors. Properly determining how much astigmatism should be incorporated into the treatment is critical. Ignoring ocular residual astigmatism and sculpting the cornea based only on manifest refraction has the penalty that the entire ocular residual astigmatism remains as postoperative surgical residual astigmatism, also resulting in induction of spherical aberrations. Centration, optical zone sizes, cyclotorsion compensation, and use of appropriate treatment algorithms are of prime importance in obtaining favorable outcomes in correction of astigmatism.