Ultra-Thin Flap Created By Low-Energy Femtosecond-Assisted Laser In Situ Keratomileusis Correct Myopia And Myopic Astigmatism One Year

To assess the safety, efficacy and stability of an ultra-thin flap (80 microns) assisted by a low-energy femtosecond for laser in suit keratomileusis (LASIK) and its outcomes in correcting myopia and myopic astigmatism during a one-year follow-up.

The study is a retrospective case series conducted at Beijing AierIntech Eye Hospital, an outpatient facility.

The study included patients who underwent femtosecond-assisted LASIK between May 2021 and November 2024. It also included those with myopia up to −12.75 D and astigmatism ranging from -0.25 to -5.25 D. The VisuMax was used for flap construction, set at 80 microns, and the laser energy ranged from 100 to 110 nJ. Patients were assessed for uncorrected and corrected distance visual acuity (UDVA, CDVA), intraocular pressure (IOP), corneal curvature, and slit-lamp examinations before and after surgery. Refractive outcomes were measured at 1 day, 1 week, and 1, 3, 6, and 12 months post-surgery. Safety efficacy and stability were evaluated using a linear mixed model (LMM) to account for inter-eye correlation.

The study enrolled 314 patients with 556 eyes (279 right, 277 left). Preoperatively, the mean spherical equivalent (SEQ) was −6.41 ± 1.77 D, and the mean astigmatism was −1.38 ± 0.94 D. One-year post-operation, the safety index was 1.24 ± 0.17, and the efficacy index was 1.15 ± 0.18; UDVA was -0.05 ± 0.70 logarithm of the minimum angle of resolution (logMAR), and CDVA was -0.09 ± 0.05. The stability of UDVA, CDVA, the safety and efficacy index, and posterior corneal surface curvature were evaluated using LMM analysis (P > 0.05). Spherical equivalent (SEQ) and surgically induced astigmatism (SIA) showed no change from 3 to 12 months, with P = 0.95 and 0.76, respectively.

Careful management of low-energy ultra-thin corneal flap LASIK surgery has proven safe and effective. Vision, refraction, and the curvature of the posterior corneal surface have remained stable during a 12-month follow-up period. The greater the amount of residual corneal stroma retained in cases of thinner corneas, high myopia and myopic astigmatism, the higher the safety.