Effects of different side-cut angles on ocular surface recovery after FS-LASIK

To compare the effects of different side-cut angles on postoperative ocular surface recovery after femtosecond laser-assisted in situ keratomileusis (FS-LASIK).

The prospective and randomized study enrolled 99 patients (198 eyes) with ametropia who underwent FS-LASIK in the Eye Institute at the Affiliated Hospital of Nantong University from September 2021 to December 2022. The patients were categorized into the 45°, 90°, and 135° side-cut angle groups. Preoperatively and at 10d, 1mo, and 6mo after surgery, patients in the three groups had their visual acuity, corneal flap edge scar, corneal region sensation, dry eye-related index changes, and nerve fiber repair at the corneal flap margin compared and analyzed.

In the groups with 45°, 90°, and 135° side-cut angles, 56, 58, and 62 eyes, respectively, finished the 6-month follow-up. The incidence of flap edge healing scar was the lowest in the 90° side-cut angle group (74.1%). At 10d postoperatively, corneal sensation at all sites decreased significantly compared with preoperative corneal sensation in the three groups (P<0.05), while patients in the 90° side-cut angle group had the highest sensation among the three groups. After surgery, the Ocular Surface Disease Index (OSDI) scores of the three groups showed a substantial rise 10d later, a reduction 1mo later, and a continued increase beyond preoperative values 6mo later (P<0.05). The 90° side-cut angle group had the lowest OSDI score at each follow-up time. At each time point after surgery, the number of eyes repaired by corneal flap nerves in the scarless group was higher than that in the scarred group (P<0.05), and the corneal flap nerve growth was relatively fast in the scarless area.

Different side-cut angles in FS-LASIK may have different effects on the postoperative ocular surface recovery. The 90° side-cut angle has a low incidence of corneal flap scar, the highest corneal sensation in the early postoperative period, and the lowest subjective dry eye symptom scores at each postoperative follow-up time. Therefore, the selection of a 90° side-cut angle for the FS-LASIK corneal flap may help patients to recover the ocular surface after surgery.