Comparative Effectiveness and Safety of Modern Corneal Refractive Surgery Techniques: SMILE versus LASIK versus PRK
Themistoklis Gialelis
ABSTRACT
Purpose: To systematically evaluate and compare the effectiveness and safety of small incision lenticule extraction (SMILE), laser in situ keratomileusis (LASIK), and photorefractive keratectomy (PRK) for myopic correction through thorough synthesis of contemporary evidence.
Methods: Systematic review was conducted following PRISMA guidelines. Comprehensive scarches were performed in PubMed/MEDLINE, Embase, Cochrane Library, Web of Science and Scopus from January 2020 to December 2025. Eligible studies included randomized controlled trials, prospective comparative studies, retrospective comparative studies, and meta- analysis comparing at least two of the three techniques for myopic correction with minimum 6-month follow-up. Primary outcomes included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive predictability (+0.50 D and +1.OO D), efficacy index and safety index. Secondary outcomes encompassed intraoperative and postoperative complications, corneal ectasia, contrast sensitivity, higher-order aberrations (coma, spherical aberration, total HOAs), and dry eye parameters (tear break-up time, Schirmer test, Ocular Surface Disease Index).
Results: From 1,034 initially identified records, 230 unique studies underwent full-text review, with 30 studies meeting inclusion criteria for qualitative synthesis. AlI techniques achieved excellent visual outcomes with efficacy indices 0.94 and comparable postoperative UDVA and CDVA SMILE produced significantly larger effective optical zones (22.18 + 2.61 mm) compared to LASIK (19.54 + 1.44 mm) and PRK (19.39 + 1.66 mm), correlating with reduced spherical aberration induction. Post-refractive ectasia incidence without identifiable preoperative risk factors was lowest for SMILE (11 per 100.000 eyes), followed by PRK (20 per 100.000), and highest for LASIK (90 per 100.000), with LASIK demonstrating 4.5-fold higher risk than PRK Dry eye symptoms were most pronounced following LASIK due to extensive corneal nerve disruption, while
SMILE showed superior preservation of corneal biomechanical integrity.
Conclusions: SMILE, LASIK, and PRK achieve comparable refraction results for myopic correction with efficacy indices exceeding 0.94 across all modalities However SMILE offers distinct advantages including larger effective optical zones, reduced higher-order aberration induction, lower ectasia risk and better preservation of corneal biomechanics and tear film stability: LASIK remains associated with higher ectasia rates and more pronounced dry eye symptoms PRK demonstrates intermediate safety profiles with prolonged visual recovery. Technique selection should be individualized based on preoperative corneal parameters, refraction error magnitude, patient occupation, and risk tolerance for specific complications.
