The visual outcomes and corneal biomechanical properties after PRK and SMILE in low to moderate myopia

Purpose: To compare the corneal biomechanical parameters, visual outcome, and epithelial remodeling after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK) for low to moderate myopia. Design: Prospective, interventional, randomized, comparative study. Methods: Eighty eyes of 40 patients undergoing bilateral SMILE or PRK for low to moderate myopia (<-5 D SE) were included. They were divided into two groups based on the planned refractive surgery. Visual acuity, corneal biomechanics using Corvis-ST, epithelial mapping via anterior segment optical coherence tomography, and higher-order aberrations were recorded both preoperatively and postoperatively at 6 months and compared. Results: At 6 months follow-up, the corrected distance visual acuity as well as the postoperative spherical equivalent of both the groups were comparable ( P = 0.13 and P = 0.32, respectively). The biomechanical parameters like deformation amplitude ratio ( P < 0.01), inverse concave radius ( P = 0.006), integrated ratio ( P < 0.01), stress–strain index ( P < 0.01), Ambrosio’s relational thickness (ArTH) ( P < 0.01), and corneal biomechanical index-laser vision correction ( P = 0.02) were altered more in the SMILE group than in the PRK group, while the biomechanically corrected intraocular pressure ( P = 0.16) was comparable. Epithelial remodeling ( P = 0.59), higher-order aberrations ( P = 0.53), and stromal keratocyte loss ( P = 0.16) in both the groups were comparable. Conclusion: Both SMILE and PRK are comparably effective procedures for correction of low to moderate myopia in terms of visual outcomes; however, the corneal biomechanical stability in PRK is superior than that in SMILE.