Ultra-Thin Flap (80-µm) Lasik Using A Low-Energy Femtosecond Laser: Safety And Predictability Of Flap Thickness

To evaluate the intraoperative and postoperative complications and predictability of flap thickness in ultra-thin flap LASIK created with a low-energy femtosecond laser.

Sadalla Amin Ghanem Eye Hospital, Joinville, SC, Brazil.

Eighty-one consecutive patients (158 eyes) with thin corneas or high percent tissue altered (PTA) were prospectively studied between August 2023 and August 2025. Flap was created using the Ziemer LDV Z8 femtosecond laser set at 80-µm thickness and diameter of 8.8 to 9.5mm. Schwind Amaris 1050Hz excimer laser was used for photoablation. Uncorrected distance visual acuity (UDVA), manifest refraction, and corrected distance visual acuity (CDVA) were assessed preoperatively, on day 1, and at 3 months postoperatively. Central epithelial thickness had a mean of 53 ± 3 µm (45 to 60 µm). Flap measurements were performed in the nasal and temporal quadrants outside the ablation zone after 3 months with anterior segment tomography (CSO MS-39).

Postoperative UDVA was statistically equivalent to preoperative CDVA (P=0.983). Safety index was 1.04. Intraoperative complications (4.4%) included focal adhesions (1.9%) and loose epithelium (1.3%). One case involved an extensive temporal adhesion with a thin, partially intraepithelial flap. Postoperative complications affected 16.7% of cases: mild interface haze (5.8%), microstriae (4.3%), and DLK grade 1 (3.6%). One eye had an interface scar after flap adherence and another a moderate interface haze. None of these eyes lost a single line of CDVA. Flap thickness averaged 84.3 ± 3.3 µm, but exhibited significant horizontal asymmetry, with the nasal side consistently thicker than the temporal side (+6 µm)(P< 0.001).

Ultra-thin (80-µm) flap LASIK is a feasible option with a favorable safety profile for patients with thin corneas or high PTA. However, variability in flap and epithelial thickness raises the risk of Bowman layer or epithelial basement membrane damage, potentially causing incomplete flaps or interface scarring.