Combining large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers for promoting protective melanosome autophagy via the PI3K/Akt/mTOR signalling pathway for the treatment of melasma.

Melasma is a common condition of hyperpigmented facial skin. Picosecond lasers are reported to be effective for the treatment of melasma. We aimed to identify the most effective therapeutic mode and elucidate the potential molecular mechanisms of picosecond lasers for the treatment of melasma. Female Kunming mice with melasma-like conditions were treated using four different picosecond laser modes. Concurrently, in vitro experiments were conducted to assess changes in melanin and autophagy in mouse melanoma B16-F10 cells treated with these laser modes. Changes in melanin in mouse skin were detected via Fontana-Masson staining, and melanin particles were evaluated in B16-F10 cells. Real-time polymerase chain reaction and western blotting were used to analyse the expression levels of melanosome and autophagy-related messenger ribonucleic acid (mRNA) and proteins. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers resulted insignificant decreases in melanin as well as in mRNA and protein expression of melanin-synthesizing enzymes (TYR, TRP-1 and MITF). This combination also led to increased expression of the autophagy-related proteins, Beclin1 and ATG5, with a marked decrease in p62 expression. Intervention with the PI3K activator, 740 Y-P, increased TYR, TRP-1, MITF, p-PI3K, p-AKT, p-mTOR and p62 expression but decreased the expression of LC3, ATG5 and Beclin1. A combination of large-spot low-fluence 1064-nm and fractional 1064-nm picosecond lasers proved more effective and safer. It inhibits melanin production, downregulates the PI3K/AKT/mTOR pathway, enhances melanocyte autophagy and accelerates melanin metabolism, thereby reducing melanin content.

The efficacy and safety of low- versus high-fluence fractional picosecond Nd:YAG 1064-nm laser in the treatment of acne scars: A randomized split-face comparison study.

BACKGROUND: Differences in clinical efficacy based on the fluence of fractional picosecond laser treatment for acne scars are unknown. OBJECTIVE: To compare the efficacy and safety of low-fluence versus high-fluence fractional picosecond Nd:YAG 1064-nm laser treatment in acne scar patients. METHODS: In this 12-week, investigator-blinded, randomized, split-face study, 25 patients with moderate-to-severe acne scars received three sessions of high-fluence laser treatment (1.0 J/cm2 ) on one side of their face and low-fluence (0.3 J/cm2 ) on the other side every 4 weeks. Patients were assessed using acne scar counts, the scar global assessment (SGA), and the ECCA scar grading scale every 4 weeks. The histological analysis compared the acne scars obtained before and 4 weeks after treatment. RESULTS: At their last visit, 88.00% and 92.00% of the subjects achieved >30% reduction in scar counts on the low- and high-fluence sides, respectively, without a significant difference between the two sides. On both sides, the scar counts, SGA, and ECCA score significantly improved 4 weeks after the last treatment. Although the high-fluence side showed a greater reduction in scar counts (-66.73%) than the low-fluence side (-62.13%), the two sides had no significant difference in the grading scores. The high-fluence side showed significantly more severe pain and higher side-effect scores immediately and 4 weeks after treatment. Histological analysis revealed a significantly increased collagen, elastin, and vimentin expression after treatment on the low-fluence side. CONCLUSIONS: The low-fluence setting demonstrated comparable efficacy and superior safety in treating acne scars compared with the high-fluence setting.

Fractional picosecond laser treatment of non-acne atrophic scars and scar erythema in Chinese patients.

BACKGROUND: Fractional picosecond lasers (FPL) are reported to be effective and safe for atrophic acne scars and post-acne erythema. However, there is no evidence regarding the effectiveness and safety of FPL treatment for non-acne atrophic scars and scar erythema among Chinese patients. METHODS: In this retrospective study, 12 Chinese patients with non-acne atrophic scars, including nine with scar erythema, were treated with one to three sessions of 1064 nm FPL treatment. Clinical improvement was objectively assessed through blinded evaluations by external physicians. A modified Manchester Scar Scale (mMSS) and the Clinician Erythema Assessment Scale (CEAS) were individually used to evaluate atrophic scars and scar erythema based on photographs. Physician-assessed and subject-assessed Global Aesthetic Improvement Scale (GAIS) were used to assess changes before and after FPL treatment. Patient satisfaction and adverse events were also documented. RESULTS: Total mMSS scores, as well as three parameters (color, distortion, and texture), were significantly decreased after FPL treatment, with a mean reduction of 3.18 ± 1.60 in total scores (p < 0.05). The CEAS scores were significantly reduced from 2.41 ± 0.98 before treatment to 0.41 ± 0.40 at the final visit (p < 0.05). Based on physician-assessed and subject-assessed GAIS scores, 11 (91.7%) patients were improved after FPL treatment. 33.3% of patients were very satisfied, and 41.7% were satisfied. No serious, prolonged (> 3 weeks) adverse events were observed. CONCLUSION: Our study suggests that 1064 nm FPL treatment may be a promising option for non-acne atrophic scars, especially with scar erythema. Further studies are needed to confirm our results.

In Vivo Evaluation of Laser-Induced Optical Breakdown (LIOBS) by 1064-nm Nd:YAG Fractional Picosecond Laser With Reflectance Confocal Microscopy and Precise Histopathologic Correlation.

OBJECTIVES: Picosecond lasers with a microlens array can cause laser-induced optical breakdown (LIOBS) and LIC (Intradermal laser-induced cavitation) within high-fluence areas. This study aimed to describe the clinical, reflectance confocal microscopy (RCM), histopathological findings, and the characteristics of vacuoles caused by LIOBS and LIC in individuals with skin types III and IV. MATERIALS AND METHODS: This study was performed on six Chilean healthy volunteers, males and females, aged 35-65 years old with Fitzpatrick skin phototypes III-IV. The laser was applied in the inner proximal area of the nondominant arm. RCM evaluation was performed 24 h later; 48 h later, skin biopsies were performed on the laser-treated areas. Clinical, histological, and RCM findings were recorded. RESULTS: Every individual developed a 10 mm2 area of clinical erythema in the treated area. Under RCM, all six volunteers had hyporeflective spherical structures at the level of the epidermis, consistent with intraepidermal vacuoles. Histopathological evaluation revealed different sizes of vacuoles in both the epidermis and dermis. CONCLUSION: The LIOBS and LIC processes and the secondary production of vacuoles could be highly valuable for effective dermal remodeling treatment and aid in promoting the production of new collagen, elastic fibers, and growth factors that could improve skin texture. These structures were visible under RCM and histopathological evaluation.

Exploring Fractional Pigment Toning: A Novel Approach for Treating Benign Pigmented Lesions in Asian Patients With Fitzpatrick Skin Types III-V.

BACKGROUND/OBJECTIVE: Laser therapy has emerged as a widely favored treatment option for solar lentigines (SL). However, a significant challenge associated with this treatment, particularly among individuals with darker skin tones, is the notable risk of postinflammatory hyperpigmentation (PIH) induction. In response to these concerns, the authors conducted a prospective, self-controlled study to comprehensively evaluate the safety and effectiveness of 532-nm picosecond laser, both with and without a microlens array (MLA), for the management of SL in patients with Fitzpatrick skin types (FST) III-V. METHODS: Twenty-seven patients with FST III-V and bilateral SL on the face underwent randomized treatment. One side of the face was treated with a 532-nm picosecond laser coupled with an MLA, utilizing the fractional pigment toning (FPT) technique, while the other side received treatment without the MLA, following the conventional technique (CT). The FPT technique utilized a 9-mm spot size with a fluence of 0.47 J/cm2 for two passes covering 40% of the area. In contrast, the CT used a 4.5-mm handpiece with fluence ranging from 0.3 to 0.7 J/cm2. Patients received a single treatment and were evaluated for pigment clearance, occurrence of PIH, and other adverse effects at 2 weeks, 1, 3, and 6 months posttreatment. RESULTS: Twenty-seven participants completed the study protocol. Analysis of pigment clearance, measured via 3D photography, showed significant improvement from 2 weeks to 6 months posttreatment for both the FPT technique (p < 0.001) and CT (p = 0.004). PIH occurred in 64%, 80%, 96%, and 88% of cases on the CT side, compared to 8%, 32%, 36%, and 16% on the FPT technique side at 2 weeks, 1, 3, and 6 months posttreatment, respectively. The incidence of PIH was significantly lower on the FPT technique side compared to the CT side throughout the follow-up periods. Additionally, transient and mild hypopigmentation occurred in one participant (4%) on the FPT technique side and in five participants (20%) on the CT side. No other adverse effects were observed during the study. CONCLUSIONS: The 532-nm picosecond laser emerges as a safe and efficacious treatment modality for SL in individuals with FST III-V. Particularly noteworthy is the efficacy of the FPT technique, which demonstrates comparable effectiveness while significantly reducing the incidence of PIH compared to the CT.

Efficacy and safety of 1064-nm fractional picosecond laser for the treatment of postmastectomy scars in transgender men: A randomized controlled trial.

OBJECTIVES: Subcutaneous mastectomy is a crucial component of gender affirmation therapy for transgender men (TM), but the scars that result from this procedure can frequently impair their quality of life. This study aimed to assess the efficacy and safety of 1064-nm fractional picosecond laser (FxPico) treatment for hypertrophic and atrophic postmastectomy scars in TM. METHODS: Twenty-two patients with a total of 35 pairs of bilateral symmetric mastectomy scars were enrolled. One of each pair of symmetric scars was randomly assigned to receive four FxPico treatments at 4-week intervals. All scars were evaluated using the modified Vancouver Scar Scale (mVSS) and three-dimensional imaging for scar roughness, melanin index, and hemoglobin index before each treatment session and at 1, 3, and 6 months following the last treatment. Additionally, participant-rated scar satisfaction (PSS) and scar improvement (Global Assessment Score, GAS), as well as adverse events were recorded. RESULTS: During the 6-month follow-up period after the end of laser treatment sessions, the treated scars showed significant reductions in the mVSS compared to the untreated controls (p < 0.001), whereas the melanin index and hemoglobin index were not significantly different. Subgroup analysis of hypertrophic scars demonstrated statistically significant reductions in mVSS at 1 (p = 0.003) and 3 months (p = 0.041) after the end of laser treatments. PSS was significantly higher on the laser-treated scars than the controls (p = 0.008), and a participant-rated GAS of 2.95 ± 0.65 was found. There were no serious adverse events reported. CONCLUSIONS: 1064-nm FxPico could be utilized to treat mastectomy scars among TM, particularly the hypertrophic type.

Wavelength-dependent threshold fluences for melanosome disruption to evaluate the treatment of pigmented lesions with 532-, 730-, 755-, 785-, and 1064-nm picosecond lasers.

BACKGROUND AND OBJECTIVES: A threshold fluence for melanosome disruption has the potential to provide a robust numerical indicator for establishing clinical endpoints for pigmented lesion treatment using a picosecond laser. Although the thresholds for a 755-nm picosecond laser were previously reported, the wavelength dependence has not been investigated. In this study, wavelength-dependent threshold fluences for melanosome disruption were determined. Using a mathematical model based on the thresholds, irradiation parameters for 532-, 730-, 755-, 785-, and 1064-nm picosecond laser treatments were evaluated quantitatively. STUDY DESIGN/MATERIALS AND METHODS: A suspension of melanosomes extracted from porcine eyes was irradiated using picosecond lasers with varying fluence. The mean particle size of the irradiated melanosomes was measured by dynamic light scattering, and their disruption was observed by scanning electron microscopy to determine the disruption thresholds. A mathematical model was developed, combined with the threshold obtained and Monte Carlo light transport to calculate irradiation parameters required to disrupt melanosomes within the skin tissue. RESULTS: The threshold fluences were determined to be 0.95, 2.25, 2.75, and 6.50 J/cm² for 532-, 730-, 785-, and 1064-nm picosecond lasers, respectively. The numerical results quantitatively revealed the relationship between irradiation wavelength, incident fluence, and spot size required to disrupt melanosomes distributed at different depths in the skin tissue. The calculated irradiation parameters were consistent with clinical parameters that showed high efficacy with a low incidence of complications. CONCLUSION: The wavelength-dependent thresholds for melanosome disruption were determined. The results of the evaluation of irradiation parameters from the threshold-based analysis provided numerical indicators for setting the clinical endpoints for 532-, 730-, 755-, 785-, and 1064-nm picosecond lasers.

Effect of fractional picosecond laser therapy using a diffractive optical lens on histological tissue reaction.

BACKGROUND AND OBJECTIVES: Fractional ablative resurfacing techniques are preferred treatments for facial rejuvenation of aged skin. This study was performed to investigate the cutaneous effects of using a fractional picosecond laser at 1064 nm with a diffractive lens. METHODS: The penetration depth according to the location of the handpiece tip was evaluated using an acrylic panel. Laser induced optical breakdown (LIOB) and cutaneous damage were observed after hematoxylin and eosin staining in guinea pigs. Collagen formation was evaluated using Victoria staining, Masson's trichrome (MT) staining, and immunohistochemical staining for collagen type III. RESULTS: The penetration depth for LEVEL 1 was 499.98-935.23 µm (average: 668.75 ± 182.84 µm); the LIOB cavity area was 1664.17 ± 650.52 µm2. The penetration depth of LEVEL 2 was 257.12-287.38 µm (average: 269.77 ± 14.55 µm) with an LIOB cavity area of 1335.85 ± 214.41 µm2. At LEVEL 3, that was 36.17-53.69 µm (average: 52.15 ± 20.81 µm) and the LIOB cavity area was 1312.67 ± 1069.12 µm2. No epidermal tissue damage was observed and collagen formation was observed from day 14 under all conditions. CONCLUSION: Diffractive optical element (DOE) lens arranged laser treatment system controlled the position of LIOB occurrence and an irradiating area.

755-nm picosecond laser plus topical 20% azelaic acid compared to topical 20% azelaic acid alone for the treatment of melasma: a randomized, split-face and controlled trial.

PURPOSE: Melasma remains a refractory skin condition that needs to be actively explored. Azelaic acid has been used for decades as a topical agent to improve melasma through multiple mechanisms, however, there is a lack of research on its combination with laser therapy. This study evaluated the effectiveness of isolated treatment with topical 20% azelaic acid and its combination with 755-nm picosecond laser in facial melasma patients. METHODS: A randomized, evaluator-blinded, controlled study was conducted on 30 subjects with facial melasma in a single center from October 2021 to April 2022. All subjects received topical 20% azelaic acid cream (AA) for 24 weeks, and after 4 weeks, a hemiface was randomly assigned to receive 755-nm picosecond (PS) laser therapy once every 4 weeks for 3 treatments. Treatment efficacy was determined by mMASI score evaluations, dermoscopic assessment, reflectance confocal microscopy (RCM) assessments and patient's satisfaction assessments (PSA). RESULTS: Treatment with 20% azelaic acid, with or without picosecond laser therapy, significantly reduced the hemi-mMASI score (P < 0.0001) and resulted in higher patient satisfaction. Improvements in dermoscopic and RCM assessments were observed in both sides of the face over time, with no difference between the two sides. RCM exhibited better dentritic cell improvement in the combined treatment side. No patients had serious adverse effects at the end of treatment or during the follow-up period. CONCLUSION: The additional use of picosecond laser therapy showed no clinical difference except for subtle differences detected by RCM assessments.The study was registered in the Chinese Clinical Trial Registry (ChiCTR2100051294; 18 September 2021).

Laser-induced optical breakdown is a prior strategy for acquired melanin-increased disorder in dermal layer.

This brief report discusses the challenges in treating dermal melanosis and the limitations of current laser treatments due to inadequate tissue penetration and potential side effects. It introduces laser-induced optical breakdown (LIOB) as a novel therapeutic approach using a picosecond laser with a diffractive lens array (DLA) to target dermal pigmentation effectively. LIOB induces multiphoton ionization, leading to melanin clearance through phagocytosis and apoptotic cell removal, while also promoting dermal remodeling and collagen synthesis. We present a case of successful treatment of dermal pigmentation in a 55-year-old woman using 755 nm-picosecond alexandrite laser therapy, demonstrating significant improvement without recurrence. The findings suggest that LIOB offers a promising solution for acquired dermal hypermelanosis by addressing both diffuse and localized pigmentation effectively, leading to skin rejuvenation with minimal downtime and high patient satisfaction.

Comparison of the 1064-nm picosecond laser with fractionated microlens array and 1565-nm non-ablative fractional laser for the treatment of enlarged pores: a randomized, split-face, controlled trial.

PURPOSE: This split-face randomized study compared the efficacy and safety between 1064-nm picosecond laser with fractionated microlens array (MLA) and 1565-nm nonablative fractional laser to treat enlarged pores. METHODS: Participants with enlarged facial pores were enrolled and underwent three consecutive sessions at 2-week intervals with either a 1064-nm picosecond laser with MLA or a 1565-nm nonablative fractional laser. Images were captured at each visit. Objective (pore number) and subjective assessments, including patient self-evaluations and quartile improvement scales, were used to evaluate the treatment efficacy. The pain levels and adverse effects were recorded at each subsequent visit. RESULTS: The participants were 3 men and 22 women with enlarged facial pores. At the initial and 2-month checkups after the last treatment, the pore numbers were significantly decreased bilaterally for both lasers. The respective quartile improvement scale scores for the 1064-nm picosecond and 1565-nm fractional lasers were 2.22 ± 1.06 and 2.14 ± 1.11, while those for patient self-assessment were 3.72 ± 0.74 and 3.68 ± 0.75. The pore number, quartile improvement scale score, and patients' self-assessments did not differ significantly between the two lasers. Treatment with the 1064-nm picosecond laser better reduced pain compared with the 1565-nm nonablative fractional laser (4.11 ± 1.33 vs. 4.83 ± 1.17). The occurrence of pigmentation did not differ significantly between the lasers. CONCLUSION: Both the 1064-nm picosecond laser with MLA and the 1565-nm nonablative fractional laser are viable options for treating enlarged pores, and showed comparable respective efficacies; however, the former was less likely to cause hyperpigmentation and was better tolerated.

A novel treatment for Riehl's melanosis targeting both dermal melanin and vessels.

BACKGROUND/PURPOSE: Riehl's melanosis is a difficult-to-treat condition characterized by persisting dermal hyperpigmentation. This study aimed to evaluate the efficacy of a histology-specific targeted therapy for Riehl's melanosis. METHODS: Skin biopsy samples of Riehl's melanosis were assessed to identify histology-specific targets for treatment. Subsequently, the efficacy of a combination involving a fractional picosecond laser and a pulsed dye laser (PDL) targeting the dermal melanin and vessels, respectively, was evaluated. Clinical improvement was assessed using the dermal pigmentation area and severity index (DPASI). The treatment outcomes were compared to those of a control, in this case a single laser treatment solely targeting pigmentation. RESULTS: Histological and immunohistochemical analyses identified dermal melanin pigment and dilated vessels as treatment targets for Riehl's melanosis. The combined treatment of the fractional picosecond laser and PDL showed a significant reduction of the DPASI scores, which was significantly better than the control group. Patients who underwent the combined laser treatment indicated high levels of satisfaction with no adverse events except of transient erythema and oedema. CONCLUSION: The combined treatment of a fractional picosecond laser and a PDL was more effective for Riehl's melanosis compared to single laser treatment. The treatment targets both dermal pigmentation and dilated vessels, offering promising results for those working to manage Riehl's melanosis.

Evaluation of the safety and efficacy of a fractional picosecond 1064 nm laser for post-acne erythema in adult Chinese patients.

OBJECTIVE: To evaluate the efficacy and safety of fractional 1064 nm picosecond Nd:YAG laser (FPNYL) in the treatment of post-acne erythema (PAE) of adult Chinese. MATERIALS AND METHODS: A total of 22 patients received 1 session of treatment and were followed up at the eighth week. Primary outcomes were measured by the Clinician erythema assessment scale (CEAS). Secondary outcomes included a global aesthetic improvement scale (GAIS) and patients' assessment of satisfaction on a five-point scale. Pain scores and adverse effects were also evaluated. RESULTS: Twenty-two patients with Fitzpatrick skin types III and IV were enrolled in the study and completed all treatments and follow-up visits. The mean CEAS scores fell from 2.74 ± 0.80 to 1.95 ± 0.75 (p < 0.05). The mean GAIS of PAE improvement was 2.46 ± 0.68. Erythema percentile scores by VISIA increased from 32.63 ± 7.0 to 45.75 ± 11.45 (t = 5.442, p = 0). The patient satisfaction score was 1.86 ± 1.17. The pain scores were 3.27 ± 1.17 for the FPNYL treatment (varied from 2 to 6). There were moderate erythema and oedema, which last for 3.84 ± 0.78 days. There were overall 68.18% (15/22) patients who felt pruritus in different degrees and 27.27% patients who encountered acne eruptions (white head type). No scar, hyperpigmentation or hypopigmentation was found. CONCLUSION: Treatment with fractional 1064 nm picosecond Nd:YAG laser is effective and safe for PAE of Chinese patients.

Efficacy and safety of low-dose oral isotretinoin monotherapy versus combined therapy with picosecond laser for the treatment of acne scars in Asian population.

PURPOSE: Acne scars are common in patients with moderate to severe acne. Isotretinoin is the first-line treatment for those patients, but whether oral isotretinoin can improve acne scar is not clear. Picosecond lasers (FxPico) has been reported to improve acne scars. In the present study, we evaluated the clinical efficacy of low-dose isotretinoin with or without FxPico treatment for acne scars. MATERIALS AND METHODS: A total of 48 patients with acne scars were enrolled and were randomly assigned to receive low dose oral isotretinoin or not. For all the patients in both treatment groups, one side of face were randomly assigned to be treated with picosecond laser. Assessments, including photos, échelle d'évaluation clinique des cicatrices d'acné (ECCA) and Global Acne Grading System (GAGS) score, the number of lesions, melanin and erythema indexes, transepidermal water loss were assessed at 0, 1, 2, and 3 month. Side effects, Dermatology Life Quality Index (DLQI) and satisfaction were recorded before and after the study. RESULTS: A total of 44 patients completed the study (24 received oral low dose isotretinoin and 20 did not). Low dose oral isotretinoin treated group showed significant improvement on ECCA (from 112.5 [50-180] to 105 [50-160]), GAGS score (from 12.6 ± 3.3 to 10.1 ± 3.0), the count of papules (from 4.3 ± 3.7 to 1.0 ± 1.5) than the blank group, and higher improvement were noticed after isotretinoin combined with FxPico. All the side effects were temporary and tolerable, no adverse effects were observed. Higher DLQI and patients' satisfaction were achieved by oral isotretinoin alone and isotretinoin combined with FxPico. CONCLUSIONS: This is the first paper showing the improvement of scars by early low dose-isotretinoin intervention with or without the combination of picosecond laser. Early intervention with oral low-dose isotretinoin is effective for the treatment and prevention of acne scars, the combined therapy with FxPico can achieve better outcome.

Efficacy and safety of fractional 1064-nm picosecond laser for atrophic traumatic and surgical scars: A randomized, single-blinded, split-scar-controlled study.

OBJECTIVE: A fractional 1064-nm picosecond laser is an efficient and safe treatment for atrophic acne scars. However, evidence of using a picosecond laser for atrophic posttraumatic and surgical scar therapy is lacking. This study aimed to evaluate the efficacy and safety of using a 1064-nm picosecond laser with a microlens array (MLA) for the treatment of atrophic posttraumatic and surgical scars. METHODS: This was a prospective, intraindividual, single-blinded, randomized split-lesion-controlled trial. Twenty-five subjects with atrophic traumatic or surgical scars that existed for more than 1 year were enrolled. All atrophic scars were divided at the midline into two halves and randomly assigned to a treatment or control side. The treatment group was treated with a 1064-nm picosecond laser with an MLA handpiece (spot size: 6-8 mm, fluence: 1.0-1.2 J/cm2 , repetition rate: 5 Hz, three passes) for 3 monthly sessions. The scar volumes were objectively measured using a three-dimensional (3D) photograph at baseline, 1 month after the first and second treatments, and 3 and 6 months after the final treatment. Subjective assessments were conducted by a blinded dermatologist and patients' self-assessment to evaluate improvements at 3 months after the final treatment. RESULTS: The treated sides exhibited a significant volume reduction, with statistically significant improvements over the control group at 1 month after the first and second treatments and at 3 months after the final treatment (p = 0.024, 0.005, and 0.019, respectively). At 3 months after the final treatment, a blinded dermatologist correctly identified the treated side in 24 of 25 patients (96%). The patients rated the improvements as excellent (>75%) and marked (50%-75%) in 36% and 48% of patients, respectively. CONCLUSION: At 3 months, the 1064-nm picosecond laser with a fractionated MLA can significantly reduce the posttraumatic and postsurgical atrophic scar volume in patients with Fitzpatrick skin types III-V. Insufficient data preclude inferences regarding efficacy at 6 months.

Morphologic and molecular biologic analyses of the skin rejuvenation effect of the fractional 1064-nm picosecond laser: An animal study.

OBJECTIVES: Application of the picosecond laser in the field of dermatology has expanded from tattoo removal to skin rejuvenation on a clinical basis. Although various mechanisms of pigment removal have been elucidated, the molecular changes associated with skin rejuvenation have yet to be identified. The aim of this study was to explore the theoretical basis and to evaluate the efficacy of skin rejuvenation using a 1064-nm fractional picosecond laser in a mouse model. METHODS: We conducted an in vivo study using a fractional picosecond laser on the skin of old and young female hairless mice and performed topographical, histological, micro-, and electron microscopic assessments. RESULTS: The topography of the skin surface was enhanced and showed increased dermal thickness on histological examination. Electron microscopy revealed disarranged collagen bundles with microspaces and vascular leakage in the upper dermis. Levels of collagen synthesis markers and various inflammatory cytokines, such as procollagens, interleukin-1ß, tumor necrosis factor-α, and heat shock proteins, were elevated in the laser-treated skin. CONCLUSIONS: This study provides a possible mechanism for the skin rejuvenation effect of fractional picosecond laser that has been reported previously in clinical observations. Based on our findings, the fractional picosecond laser could be widely applied in clinical settings where dermal regeneration and promotion of skin rejuvenation is required.

Comparison of the efficacy and safety of a 730 nm picosecond titanium sapphire laser and a 755 nm picosecond alexandrite laser for the treatment of freckles in Asian patients: A two-center randomized, split-face, controlled trial.

OBJECTIVE: The 730 nm picosecond titanium sapphire laser is a novel laser that shows promising results in treating freckles. This study aimed to further investigate the efficacy and safety of the 730 nm picosecond titanium sapphire laser for treating freckles in Asian patients compared with those of the 755 nm picosecond alexandrite laser. METHODS: Each face of 86 participants was split into two parts and randomly assigned either one session of 730 or 755 nm picosecond-laser treatment each. Efficacy and safety were determined based on blinded visual evaluations and self-reports at each follow-up visit. RESULTS: The treatment outcomes of the 730 nm picosecond laser for the treatment of freckles were comparable to those of the 755 nm picosecond laser, with 68.99 ± 7.42% and 69.27 ± 7.75% clearance, respectively (p > 0.05). Participants achieved similar Global Aesthetic Improvement Scale scores (4.04 ± 0.31 vs. 4.02 ± 0.30, respectively [p > 0.05]). Additionally, the 730 nm picosecond laser was perceived to be less painful than the 755 nm picosecond laser (4.69 ± 1.63 vs. 5.65 ± 1.80 nm, p < 0.0001). CONCLUSION: The 730 nm picosecond laser is safe and effective for the treatment of freckles in Asian patients. Besides, the 730 nm picosecond laser is less painful than the 755 nm picosecond laser.

Nonlinear absorption-based analysis of energy deposition in melanosomes for 532-nm short-pulsed laser skin treatment.

BACKGROUND AND OBJECTIVES: The clinical use of 532-nm short-pulsed lasers has provided effective treatment of epidermal pigmented lesions. However, the detection of significant differences in treatment effects between picosecond and nanosecond lasers has still varied among clinical studies. For robust evaluation of the differences based on the treatment mechanism, this study presents a nonlinear absorption-based analysis of energy deposition in melanosomes for 532-nm short-pulsed laser treatment. STUDY DESIGN/MATERIALS AND METHODS: Nonlinear absorption by melanin is modeled based on sequential two-photon absorption. Absorption cross-sections and nonradiative lifetimes of melanin, which are necessary for the nonlinear absorption-based analysis, are determined from transmittance measurement. Using the model and parameters, energy deposition in melanosomes was calculated with varying fluence and pulse width settings, including actual clinical parameters. RESULTS: The energy deposition in melanosomes increased with shorter laser pulses, and subnanosecond laser pulses were found to be most efficient. The comparison of energy deposition calculated using clinical parameters demonstrated the differences in treatment effects between picosecond and nanosecond lasers reported in clinical studies. CONCLUSION: The nonlinear absorption-based analysis provides quantitative evidence for the safety and efficacy evaluation of short-pulsed laser treatments, which may lead to the establishment of numerical indices for determining treatment conditions. Future studies considering the effects of the surrounding tissue on energy deposition in melanosomes will be needed.

Efficacy and safety of picosecond laser for the treatment of melasma: a systematic review and meta-analysis.

Multiple laser modalities have been used for melasma treatment. However, the effectiveness of picosecond laser in treating melasma remains unclear. This meta-analysis investigated the effectiveness and safety of picosecond laser for melasma treatment. Randomized controlled trials (RCTs) comparing picosecond laser with conventional treatment for melasma were searched through five databases. The melasma area severity index (MASI)/modified MASI (mMASI) was used to quantify the degree of melasma improvement. Standardized mean differences and 95% confidence intervals were calculated using Review Manager for result standardization. Six RCTs, which used picosecond laser at 1064, 755, 595, and 532 nm wavelengths, were included herein. Picosecond laser significantly reduced the MASI/mMASI, but the results were highly heterogeneous (P = 0.008, I2 = 70%). In the subgroup analysis of 1064 and 755 nm picosecond lasers, 1064 nm picosecond laser significantly reduced the MASI/mMASI with no significant side effects (P = 0.04). Meanwhile, 755 nm picosecond laser did not significantly improve the MASI/mMASI compared with topical hypopigmentation agents (P = 0.08) and caused post-inflammatory hyperpigmentation. Other laser wavelengths could not be used in the subgroup analysis owing to an insufficient sample size. Picosecond laser at 1064 nm is safe and effective for melasma treatment. Picosecond laser at 755 nm is not superior to topical hypopigmentation agents in treating melasma. The exact efficacy of other wavelengths of picosecond laser for melasma treatment remains to be verified in large-scale RCTs.

An update on fractional picosecond laser treatment: histology and clinical applications.

Picosecond lasers have a very short pulse duration and a high peak power density. When fractional optical delivery systems are attached to picosecond lasers, they generate an array of concentrated microspots with a high fluence surrounded by areas with a low fluence. This article discusses the histologic characteristics and clinical applications of fractional picosecond laser treatment. Fractional picosecond laser produces laser-induced optical breakdown (LIOB) and laser-induced cavitation (LIC) in the epidermis and dermis respectively, and can encourage skin regeneration and dermal remodeling. It has been shown that fractional picosecond laser has a positive effect on facial photoaging, enlarged facial pores, dyspigmentation, wrinkles, and atrophic scars. Further research is still needed to confirm the benefits of fractional picosecond lasers.