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

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.

Prospective, interventional, randomized, comparative study.

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.

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.

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.