Effect Of Femtosecond Laser Settings On Early Visual Outcomes After Corneal Lenticule Extraction For Advanced Refractive Correction (Clear) Surgery.

To compare the effect of the femtosecond laser power settings on early visual outcomes after corneal lenticule extraction for advanced refractive correction (CLEAR) for myopia and myopic astigmatism.

Initial single-site surgical experience with CLEAR (Eyeonce Eye Clinic, Seoul, South Korea).

Initial 120 eyes (60 patients) underwent CLEAR surgery using the FEMTO LDV Z8 femtosecond laser (Ziemer Ophthalmic Systems AG). Slit lamp corneal marking was performed to compensate for cyclotorsion. Optical zone was 6.3-6.5 mm, cap thickness was 110-120 µm. First 60 eyes were treated with the initial laser power settings that ensure smooth lenticule interfaces’ dissection (Group 1, laser power 33%/36%), whilst the next 60 eyes with optimal laser power to ensure smooth dissection of the lenticule interfaces with minimal gas bubble layer formation in the interface during the cut (Group 2, laser power 30%/31%). Visual acuity and refractive error were compared between the two groups at 1 day, 2 weeks, and 1 month after surgery.

Mean age of Group 1 was 27.4±6.3 years and 26.2±6.4 years for Group 2. No statistical difference was observed in preoperative manifest refraction between the two groups. Uncorrected distance visual acuity (UDVA) at 1 day, 2 weeks, and 1 month was 0.17±0.14, 0.05±0.08 and 0.01±0.07 LogMAR in Group 1, respectively, and 0.09±0.09, 0.02±0.05 and -0.03±0.05 LogMAR in Group 2, respectively, (1 day: p<0.001, 2 weeks: p=0.013, 1 month: p=0.008). Refractive outcomes showed no statistically significant difference between the two groups except for mean cylinder power at 2 weeks (Group 1: -0.47±0.23 D, Group 2: -0.34±0.21 D, p=0.0043). In both groups, lenticule interfaces’ dissections were very smooth in all cases without any complications.

Smooth lenticule interfaces’ separation, easy lenticule removal and no intraoperative complications were observed in all cases independently from the laser power settings used. However, the use of optimal laser power settings (Group 2) provided a statistically significant faster visual recovery. These laser power settings’s adjustments shall be considered as a balance between very smooth dissection of the lenticule interfaces—with minimum to no adherence—and risk for gas bubble layer formation in the interface during the lenticule cut.