Treatment of facial and non‐facial lentigines with a 730 nm picosecond titanium: Sapphire laser is safe and effective
Authors: Kauvar Arielle N. B. , Sun Rongrong , Bhawan Jag , Singh Gaurav , Ugonabo Nkem , Feng Hao , Schomacker Kevin 
Published: August 2021

Objective

A 730 nm picosecond‐domain laser was developed to improve the clearance of pigmented lesion and reduce adverse events. This study assessed the safety and efficacy of this system for the clearance of lentigines and explores how the short picosecond pulses interact with tissue via histology.

Study Design and Methods

Twenty subjects with Fitzpatrick skin types II–IV were enrolled in this prospective, IRB‐approved study. Four treatments were administered using a 730 nm picosecond‐domain laser. Pre‐ and posttreatment photos were assessed by blinded reviewers at 4‐ and 12‐week follow‐up visits, using a 5‐point clearance scale. Subject satisfaction was measured using a 5‐point scale. Investigator Global Improvement Score (IGIS) was performed at the 4‐ and 12‐week follow‐up visits, using an 11‐point clearance scale. Subject pain level was measured using an 11‐point scale (no pain [0], extreme pain [10]). Histology of 730 and 532 nm picosecond pulses was compared with 755 and 532 nm nanosecond pulses.

Results

Sixteen subjects with a total of 118 discontinuous treatment areas, each comprised of 1–20 lesions, completed all study visits. Thirty body regions were studied, including arms (6), hands (16), scalp (1), forehead (2), face (3), and back (2). Spot sizes ranging from 2 to 5 mm diameters were used with fluences ranging from 0.8 to 4.0 J/cm2. Mean pain score was 3.6 of 10 for all four treatments. Ninety‐nine percent of randomly paired 4‐week posttreatment images and 100% of 12‐week posttreatment images were correctly identified from their respective baseline images by three blinded reviewers. Mean IGIS demonstrated scores of 6.7 and 7.0 at 4‐ and 12‐week follow‐up visits, respectively. At the 4‐ and 12‐week follow‐up visits, 76% and 73% of subjects, respectively, were satisfied to highly satisfied. The mean clearance score for all 118 treatment areas was 3 of 4 in follow‐up visits. At 12‐week follow‐up, 36% of 118 treatment areas had a clearance score of 4, and 38% had a clearance score of 3. Post treatment, there was typical erythema, edema, dryness, crusting, and itching but negligible purpura, no pinpoint bleeding, blistering or scarring, and no significant hyperpigmentation or hypopigmentation. Histology showed diffuse, focal epidermal vacuolization ~5–10 µm in diameter and mild extravasation of erythrocytes with 730 nm picosecond pulses, while diffuse epidermal vacuolization was observed with coalescence of vacuoles (~20–100 µm), junctional clefting and mild extravasation of erythrocytes with 755 nm nanosecond pulses. Picosecond pulses of the wavelength of 532 nm produced diffuse, focal epidermal vacuolization and larger dermal vacuoles to depths of 500 µm, while 532 nm nanosecond pulses produced diffuse epidermal vacuolization with coalescence of vacuoles and marked dermal hemorrhage.

Conclusion

This study demonstrated the potential of a new 730 nm picosecond‐domain laser for the clearance of lentigines. The results showed good clearance with no adverse events and good subject satisfaction in patients with skin type II–III. Additional studies need to be conducted on darker skin types. The histopathologic findings demonstrate that the picosecond 730 nm laser produces excellent selectivity for pigment with minimal disruption of the dermal–epidermal junction and may therefore reduce healing times and the risk of adverse events.