Efficacy and Safety of 1.5- and 3.0-mm High-Intensity Focused Ultrasound for Eyebrow Lifting in Korean Adults: A Prospective Randomized Split-Face Study.

BACKGROUND

High-intensity focused ultrasound (HIFU) is widely used for noninvasive eyebrow lifting, but within-subject comparisons of cartridge focal depths are scarce.

OBJECTIVE

To evaluate the efficacy and safety of 1.5- and 3.0-mm cartridges for eyebrow lifting in Korean adults, with an exploratory between-depth comparison.

METHODS

In this randomized split-face study, 20 Korean adults were treated once with the 1.5-mm cartridge on one side and the 3.0-mm contralaterally (225 J/side). Average and maximum eyebrow heights (AEH, primary; MEH, secondary) were measured from standardized photographs at baseline, post-treatment, and weeks 1, 4, and 12. Satisfaction, pain, and adverse events were recorded.

RESULTS

Both measures increased significantly at all time points (unadjusted p < 0.05). At week 12, AEH increased by 1.76 ± 1.19 mm (1.5-mm) and 1.23 ± 1.33 mm (3.0-mm); 98.75% one-sided CI lower bounds (1.10 and 0.51 mm) met the corrected primary efficacy criterion. MEH met the separately corrected criterion with the 1.5-mm (0.57 mm) but not the 3.0-mm cartridge (-0.08 mm). The exploratory week-12 AEH difference was nonsignificant (p = 0.116). No treatment-related adverse events occurred over 12 weeks, supporting short-term tolerability in this cohort rather than definitive safety.

CONCLUSIONS

Each cartridge was associated with significant within-subject increases in photographic eyebrow-height measures through 12 weeks and high satisfaction, although the corrected MEH criterion was not met with the 3.0-mm cartridge. Without a sham control, findings indicate within-subject improvement, not causal efficacy; the between-cartridge comparison is inconclusive, not evidence of equivalence. Larger, sham-controlled studies are needed.