SMILE vs. LASIK: Does Corneal Shape Affect Vision Correction Outcomes?
"New research reveals how corneal curvature impacts the precision of SMILE and LASIK, potentially affecting astigmatism and higher-order aberrations."
Achieving optimal vision correction hinges on precise centration during procedures like SMILE (small-incision lenticule extraction) and LASIK (laser-assisted in situ keratomileusis). While both aim to correct refractive errors, the shape of your cornea and how these techniques interact with it can subtly influence the outcome. Imperfect centration can lead to halos, monocular diplopia, or reduced visual acuity, making it essential to understand the factors that contribute to accurate alignment.
Technological advancements like active eye trackers and iris registration have significantly minimized decentration in excimer laser platforms. However, a degree of subclinical decentration can still occur, potentially inducing higher-order aberrations (HOAs) that affect vision quality. This is especially relevant in SMILE, where centration relies more on patient fixation and surgeon technique compared to LASIK's active alignment mechanisms.
A recent study investigated the association between anterior corneal curvature, optical zone centration, and their impact on aberration profiles following SMILE and LASIK. By analyzing a group of patients undergoing either procedure, the researchers aimed to uncover how the eye's natural shape might play a role in the precision and visual outcomes of these popular vision correction methods.
Why Corneal Shape Matters
Corneal shape is central to how refractive procedures alter the eye's focusing power. For patients considering SMILE or LASIK, the relevant outcomes can include clearer vision and reduced reliance on glasses or contact lenses, but results may vary with individual anatomy and clinical factors. Comparisons therefore require attention to more than the procedure name alone.
LASIK and SMILE in Practice
LASIK and SMILE are laser-based procedures designed to correct refractive errors associated with the cornea, and both may reduce dependence on glasses or contact lenses. LASIK, approved by the FDA in 1995, is widely used and can address nearsightedness, farsightedness, and other refractive errors, while SMILE uses a smaller incision rather than a LASIK flap. Reported trade-offs include SMILE's historical concerns about post-docking adjustments, cyclotorsion, and centration in the United States, whereas LASIK may offer faster early clarity for patients who need crisp vision within a few days.
An Evolving Field
Laser vision correction has developed through successive generations of procedures and technology. LASIK became an established option before SMILE emerged as a newer small-incision approach. The comparison between them continues to evolve as clinicians assess how surgical design and corneal shape affect outcomes.
Corneal Curvature and Centration: What the Research Reveals
The study, encompassing 78 eyes, assessed optical zone centration by analyzing curvature difference maps between pre- and postoperative scans. Researchers correlated anterior keratometry values (measurements of corneal curvature) with the degree of optical zone decentration. They further investigated the effect of decentration on astigmatic correction and the induction of higher-order aberrations (HOAs).
- Astigmatism Matters: In SMILE, a significant correlation emerged between anterior keratometric astigmatism and decentration distance. This suggests that the degree of astigmatism (irregular corneal shape) influences treatment centration in SMILE.
- LASIK's Different Path: No such correlation was found in LASIK, indicating that the procedure's centration is less affected by the eye's inherent astigmatism.
- Decentration and Aberrations: Subclinical decentration, regardless of the procedure, was associated with the induction of total coma and total HOAs. However, it didn't significantly impact lower-order astigmatic correction.
Recent Comparative Evidence
A 2026 Frontiers report found that SMILE had the highest refractive predictability and long-term stability in its comparison, with postoperative spherical-equivalent values closest to emmetropia and the narrowest distribution of residual refractive error at follow-up intervals. A 2024 study likewise described both SMILE and wavefront-guided LASIK as safe and effective for myopia and astigmatism, but reported that wavefront-guided LASIK had a lower surgical angle of error, a higher cylinder correction index, and less induced coma than SMILE. In contrast, an American Academy of Ophthalmology report described a newer ray-tracing-guided LASIK procedure as outperforming SMILE Pro in a head-to-head study, showing that findings can differ with the technology and endpoints examined.
Similar Results, Different Limitations
A 2021 review described SMILE as a relatively young refractive procedure that was producing results similar to advanced LASIK. The same review emphasized that SMILE was not without issues and examined the relative merits of both procedures alongside results from well-performed studies. This supports a cautious comparison rather than assuming that one operation is universally superior.
Tissue, Stability, and Range
SMILE preserves a greater amount of corneal tissue, which may contribute to enhanced corneal biomechanics, and it is effective for myopia and astigmatism. LASIK creates a corneal flap, which may affect corneal stability, but it is versatile and can address myopia, hyperopia, and astigmatism. The Cleveland Clinic presents both procedures as options whose advantages and disadvantages should be considered in relation to the patient's needs.
Implications for Vision Correction
The study's findings underscore the importance of considering corneal shape, especially astigmatism, when planning SMILE procedures. While the study demonstrates that corneal astigmatism affects treatment centration in SMILE but not LASIK, both procedures demonstrated that subclinical decentration was associated with the induction of total coma and total HOA, which did not affect astigmatic outcomes.
Individualized Decision-Making
The available comparisons suggest that corneal shape is one part of a broader clinical decision. SMILE and LASIK can both provide effective refractive correction, but their surgical designs create different considerations for tissue preservation, centration, early visual recovery, and treatment range. A qualified eye-care professional must weigh those factors for the individual patient rather than treating either procedure as universally best.
Technology and Adoption
The LASIK market is projected by one 2025 source to grow from 2026 through 2033, driven by consumer demand, technological advances, and global industry trends. A 2026 trends article identifies innovations in technology, clinical outcomes, safety profiles, and future directions, while describing SMILE as offering reduced dry-eye incidence and biomechanical preservation. Another source calls SMILE one of the fastest-growing refractive procedures worldwide, although PRK and SMILE also represent competition for the LASIK market.
Disease and Retreatment Considerations
A study of LASIK outcomes in patients with controlled systemic diseases examined safety, efficacy, and predictability rather than assuming that all patients have identical surgical circumstances. Retreatment is another systemic consideration: a Nature source reports that LASIK retreatments are more manageable through flap lift and ablation, whereas SMILE retreatment is more complicated. Common SMILE retreatment options include surface ablation, according to that source.
Experience and Quality of Life
A single-site surgical experience with SMILE compared its findings with the FDA SMILE study and with LASIK platforms from 1999–2000 and 2013–2016. Separately, a quality-of-life study was designed to compare long-term postoperative quality of life and satisfaction between SMILE and FS-LASIK for myopia correction. These sources underscore that real-world evaluation includes surgical experience, patient satisfaction, and quality of life alongside refractive measurements.
Although subclinical decentration influences total coma and total HOA induction, it's reassuring to note that the lower-order astigmatic correction isn't affected. This suggests that while subtle vision quality differences might arise, the primary correction of astigmatism remains reliable.
Ultimately, this research contributes to a deeper understanding of the nuances of SMILE and LASIK, empowering surgeons to refine their techniques and provide patients with even more predictable and optimized visual outcomes. Further research with longer follow-up durations are needed to confirm these findings, paving the way for advancements in vision correction.