Functional Optical Zone and Centration Following SMILE and LASIK: A Prospective, Randomized, Contralateral Eye Study

Area of Science:

• Ophthalmology
• Refractive Surgery
• Corneal Surgery

Background:

• Small Incision Lenticule Extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK) are common procedures for myopia correction.
• Understanding the differences in optical outcomes between SMILE and LASIK is crucial for patient selection and surgical planning.

Purpose of the Study:

• To compare the functional optical zone (FOZ) and centration after SMILE versus LASIK.
• To evaluate visual outcomes and aberrations following these two refractive surgery techniques.

Main Methods:

• A prospective, randomized, single-masked, paired-eyed clinical trial involving 70 patients.
• SMILE was performed on one eye and LASIK on the fellow eye for myopia and myopic astigmatism.
• Functional optical zone (FOZ) was calculated using refractive power maps, and centration was assessed by measuring distances between the FOZ centroid, pupil center, and corneal apex.

Main Results:

• Visual acuity and refractive outcomes were comparable between SMILE and LASIK.
• SMILE resulted in a significantly larger FOZ compared to LASIK (30.25 vs 29.21 mm²), despite a smaller programmed optical zone.
• Postoperative spherical aberration increase was lower after SMILE than LASIK (0.08 vs 0.17 µm). Pupil and apex centration were similar between the groups.

Conclusions:

• SMILE creates a larger functional optical zone than LASIK, potentially due to differing biomechanical responses.
• Both SMILE and LASIK offer comparable visual outcomes and centration.
• The findings suggest SMILE may offer advantages in achieving a wider optical zone for refractive correction.