Flat optic vs. diffractive lens array delivery of 755‐nm picosecond alexandrite laser for melasma‐associated photoaging in Asian skin: a randomized split‐face trial with 2‐year follow‐up
Description
Facial rejuvenation in darker-skinned individuals, particularly Asians, is challenging due to high risks of post-inflammatory hyperpigmentation (PIH). The 755-nm picosecond alexandrite laser (PSAL) offers a promising alternative through its photomechanical mechanism, yet comparative data between its two delivery modes—flat optic and diffractive lens array (DLA)—remain limited. This split-face randomized controlled trial compared these two modalities in 78 Asian women with melasma. Each participant received six monthly split-face treatment sessions. Evaluations included clinical, photographic, patient-reported, and histologic analysis over two years. Results showed both modalities yielded comparable long-term improvements in photoaging and melasma, with equivalent increases in collagen I/III and elastin levels. Flat optic provided faster pigment clearance, while DLA showed earlier improvement in texture and wrinkles. Crucially, flat optic demonstrated superior safety, with significantly lower PIH incidence (35.9% vs. 60.3%, p=0.0023), less pain, and shorter recovery time. Among those developing PIH, 60.7% with flat optic recovered within one week versus 25.5% with DLA, where 27.7% had recovery exceeding four weeks. Based on these findings, we propose a new, refined treatment paradigm: flat optic emerges as the preferred initial intervention for PIH-prone patients seeking rejuvenation, DLA may be reserved for subsequent structural enhancement once pigment has been stabilized.