What are the long-term outcomes of Small Incision Lenticule Extraction (SMILE) and Laser-Assisted In Situ Keratomileusis (LASIK) procedures after 20 years?

Long-term Outcomes of SMILE and LASIK After 20 Years

Both SMILE and LASIK procedures demonstrate excellent long-term stability and safety, with SMILE showing potentially better outcomes for corneal biomechanics and dry eye symptoms, while LASIK offers superior visual outcomes with the latest technology platforms.

Efficacy and Stability

Visual Outcomes

• A 10-year follow-up study of SMILE found no significant change in postoperative refractive error compared to 6-month results, with a mean spherical equivalent of -0.35 ± 0.66 D 1
• In the FDA premarket clinical trial for SMILE, 95.3% of patients were within 0.50 D of emmetropia at 12 months 1
• Five-year comparative studies show 98% of SMILE-treated eyes and 95% of FS-LASIK eyes achieved postoperative logMAR UDVA of 0 or better 2
• Wavefront-guided LASIK demonstrated superior visual outcomes with 94% of eyes achieving ≥20/20 UDVA compared to 83% with SMILE at 12 months 1

Refractive Stability

• Long-term studies (minimum 10 years for LASIK/PRK and 5 years for SMILE) show high levels of safety with rare late complications 3
• Minimal regression was observed in both procedures within recommended indications:
  • SMILE: -0.02 ± 0.39 D regression between 6 months and 5 years
  • FS-LASIK: -0.12 ± 0.32 D regression between 6 months and 5 years 2

Comparative Advantages

SMILE Advantages

• Preserves anterior stroma (60% of corneal tensile strength) by avoiding flap creation 1
• Reduces dry eye symptoms by preserving the sub-basal nerve plexus 1
• May have advantages for high myopia (≥ -6.00 diopters) 1
• Lower rate of ectasia than LASIK and PRK (though not completely protective) 1
• Better OSDI scores and tear break-up time compared to FS-LASIK 4

LASIK Advantages

• Superior visual outcomes with latest technology platforms 5
• Faster visual recovery and better low-contrast visual acuity 1
• Better effective centration with topographically guided procedures 1
• Preferred for treatment of hyperopia and cases with significant higher order aberrations 6

Complications and Side Effects

SMILE Complications

• Intraoperative complications include suction loss, opaque bubble layer, and black spots 1
• Surgical challenges: cap-lenticule adhesions, difficult dissection, lenticule tears, cap perforation 1
• Retained lenticule fragments may cause irregular astigmatism 1
• Steeper learning curve compared to LASIK 1

LASIK Complications

• Flap-related complications (displacement, striae, epithelial ingrowth)
• Higher incidence of dry eye symptoms that may persist longer 4
• Slightly higher regression rate compared to SMILE (though not statistically significant) 2

Dry Eye Outcomes

• SMILE shows milder subjective dry eye symptoms compared to FS-LASIK 4
• At 6 months postoperatively:
  • TBUT values returned to preoperative levels in both procedures
  • OSDI scores returned to baseline in SMILE but remained impaired in FS-LASIK
  • SIT values remained statistically impaired in both groups 4

Patient Selection Considerations

• SMILE may be preferred for:

  • Patients with mild dry eye preoperatively
  • Patients likely to engage in contact sports
  • High myopia cases (≥ -6.00 diopters) 6

• LASIK may be preferred for:

  • Hyperopia correction
  • Cases with significant higher order aberrations
  • Cases with topographic irregularities 6

Important Caveats

• Most long-term studies have limited follow-up (10 years maximum for most procedures)
• Technological improvements in diagnostics and lasers likely make current treatments safer and more stable than earlier generations 3
• Surgeon experience significantly impacts SMILE outcomes due to its steeper learning curve 1
• Both procedures may require retreatment for residual refractive errors, with SMILE having more limited retreatment options 1