Comparison of Low Laser Energy Dose in KLEx: Short-term Clinical Results, Video Analysis, and Histologic Study of Lenticules.

PURPOSE: To investigate the effects of reducing pulse energy and total energy dose during keratorefractive lenticule extraction (KLEx) using the ATOS femtosecond laser (SCHWIND eye-tech-solutions GmbH) on early surgical outcomes and corneal surface roughness.

METHODS

This study included 80 patients (160 eyes) who underwent KLEx for myopia correction at a single clinic. Eyes were divided into three groups according to energy settings: a conventional energy group (90 nJ, spot/track distance 3 × 3 μm, 1,000 mJ/cm2; C-group, 58 eyes), a low energy group (80 nJ, 4.5 × 3 μm, 593 mJ/cm2; L-group, 52 eyes), and a very low energy group (75 nJ, 6.5 × 2.9 μm, 398 mJ/cm2; VL-group, 50 eyes). Uncorrected distance visual acuity and mean spherical equivalent were evaluated at 1 day, 1 week, 1 month, and 3 months postoperatively. Intraoperative opaque bubble layer (OBL) and black areas were assessed using surgical video analysis. Surface roughness of selected lenticules was evaluated by scanning electron microscopy (SEM).

RESULTS

Uncorrected visual acuity (logarithm of the minimum angle of resolution [logMAR]) improved with lower energy levels at 1 day (C: 0.16, L: 0.05, VL: 0.00; P < .001), 1 week, and 1 month (P < .05), with the VL-group demonstrating the fastest early visual recovery. Mean spherical equivalent showed no significant differences among groups at 1 week, 1 month, or 3 months postoperatively. Black area incidence was similar between groups. However, OBL area increased with higher energy levels. SEM analysis showed the highest lenticule surface regularity score in the L-group (13.58), followed by the VL-group (10.00) and C-group (6.50).

CONCLUSIONS

When performing KLEx surgery with the ATOS device, lowering the pulse energy and applying asymmetric spacing settings led to faster early visual recovery and reduced intraoperative OBL occurrence. The smoothest lenticule surface was observed in the L-group, whereas the VL-group showed a tendency toward increased surface roughness. These findings suggest the importance of balancing early visual recovery and surface smoothness when selecting low energy settings. Further evaluation of long-term surgical outcomes and corneal effects is warranted.