Immediate skin responses to laser and light treatments

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.

Assessment of adverse events for a home-use intense pulsed light hair removal device using postmarketing surveillance

BACKGROUND AND OBJECTIVES

Home-use intense pulsed light (IPL) hair removal devices are convenient for consumers. Consumer safety associated with home-use IPL devices, however, remains a subject of interest. In this descriptive analysis, we assessed the most commonly reported adverse events (AEs) for a home-use IPL device from postmarketing surveillance and qualitatively compared these with AEs from clinical studies and medical device reports of home-use IPL treatments.

MATERIALS AND METHODS

For this analysis of voluntary reports, we queried a distributor's postmarketing database for IPL devices for the period beginning January 1, 2016, to December 31, 2021. All sources of comments, for example, phone, e-mail, company-sponsored web sites, were included in the analysis. AE data were coded according to the Medical Dictionary for Regulatory Activities (MedDRA) terminology. Also, we conducted a PubMed search to identify AE profiles from existing literature on home-use IPL devices and we searched the Manufacturer and User Facility Device Experience (MAUDE) database for reports on home-use IPL devices. These results were qualitatively compared to the data in the postmarketing surveillance database.

RESULTS

A total of 1692 cases involving IPL were identified from voluntary reports of AEs between 2016 and 2021. The shipment-adjusted reporting rate for AE cases (number of AE cases/100,000 shipped IPL devices) was 67/100,000 during this 6-year period. The most commonly reported AEs were pain of skin 27.8% (470/1692), "thermal burn" 18.7% (316/1692), and erythema 16.0% (271/1692). Among the top 25 AEs reported, no unexpected health events were observed. The reported AEs were qualitatively similar to the pattern seen in clinical studies and the MAUDE database associated with such home-use IPL treatments.

CONCLUSION

This is the first such report documenting AEs for home-use IPL hair removal from a postmarketing surveillance program. These data are supportive of the safety of such home-use low-fluence IPL technology.

Laser Treatment of Hypopigmentation in Scars: A Review

BACKGROUND

Despite history of multiple treatment modalities, repigmentation of hypopigmented scars remains a difficult clinical problem.

OBJECTIVE

The purpose of this review is to evaluate the literature on laser and combination laser plus adjunct topical therapy for hypopigmented burn and traumatic scars.

MATERIALS AND METHODS

A search on PubMed and on Oxford Academic was conducted with additional relevant literature obtained from reference lists.

RESULTS

Treatment regimens that address hypopigmentation within scars were reviewed. A combination of nonablative fractional or ablative fractional laser treatment with topical prostaglandin analogue with or without topical retinoid were found to result in superior repigmentation.

CONCLUSION

Reliable improvement of hypopigmentation in scars after laser treatment is challenging. Laser can achieve success in some cases. Ultraviolet laser can achieve modest repigmentation; however, results are short-lived and require continued re-treatment. Modest improvement in pigmentation is seen with nonablative fractional laser or ablative fractional laser alone and enhanced repigmentation is demonstrated when combining fractional laser resurfacing with topical application of synthetic prostaglandin analogues and other known modulators of melanogenesis.

The Optimal Application of Medium Potency Topical Corticosteroids in Preventing Laser-Induced Inflammatory Responses-An Animal Study

Background: During ablative fractional resurfacing (AFR) laser therapy, thermal damage to the skin is inevitable, resulting in inflammatory responses and small wounds. Corticosteroids are known for their anti-inflammatory effect. However, inappropriate application of corticosteroids carries the risk of delayed wound healing. Therefore, we aimed to find the optimal administration route, timing, and duration of medium potency corticosteroid treatment to prevent AFR laser-induced inflammatory responses and to minimize the risk of delayed wound healing. Methods: We determined the anti-inflammatory efficacy of corticosteroids by skin erythema and tissue biopsies on C57BL/6 mice. Wound healing was evaluated by crust area and epithelial gap. Finally, Masson’s trichrome stain and α-SMA immunohistochemistry stain were used to analyze scar contracture. Results: Our results demonstrated that one dose of medium-potency topical corticosteroid applied immediately after AFR laser treatment could prevent erythema effectively with minimal disruption to wound healing. Notably, when more than one dose was administered, wound healing was delayed and scar contracture was aggravated by the application of medium-potency topical corticosteroids in a dosage-dependent manner. Conclusion: Our findings suggested that single-dose medium-potency topical corticosteroids could potentially improve AFR laser-induced acute inflammatory responses in clinical applications.

Light-based treatment of pediatric port-wine birthmarks

Port-wine birthmarks (PWBs) are progressive vascular malformations with significant disfigurement and psychosocial morbidity; early light-based treatment has shown improved outcomes in the pediatric population. Somatic mosaic mutations underly the progressive nature of PWBs and explain the significant differences in response and heterogeneity of vessel architecture in the pediatric population when compared to the adult cohort. Here, we summarize a review of pediatric specific literature on the various light-based treatment modalities, including pulsed dye laser, near-infrared lasers, and intense pulsed light, providing the various indications, tips, advantages, and disadvantages for the pediatric dermatologist.

Management and prevention of laser complications in aesthetic medicine: An analysis of the etiological factors

Growing popularity of laser treatment has understandably resulted in increased incidence of potential complications. The analysis of complications, taking into account the causes of their occurrence, is of particular interest. The identification of etiological factors and the development of a step-by-step prophylactic algorithm with their consideration is the way to reduce the number of possible complications in future practice. In this article, we present a classification of the causes of complications associated with various types of laser procedures. This classification was developed on the basis of a review of last 20 years' literature and our own experience in a network of clinics "Linline" in Russia. We identified six groups of the etiological classification of laser complications: errors of patient selection, errors of treatment tactics, wrong choice of device and technology, neglect of treatment protocol, inadequate post-procedural care, individual response of the patient. The causes of all specified groups of complication, except the last one, are preventable causes.

Dynamic Optical Coherence Tomography Imaging of Telangiectasia Prior to Intense Pulsed Light Treatment-An Opportunity to Target Treatment?

BACKGROUND AND OBJECTIVES

To investigate whether optical coherence tomography (OCT) could be utilized to characterize blood flow and vessel dimensions of facial telangiectasias before and during consecutive intense pulsed light (IPL) treatment.

STUDY DESIGN/MATERIALS AND METHODS

Dynamic OCT (D-OCT) was used to image telangiectasia immediately before and after, 1-3 days after, and 1 month after IPL treatment. Measurements included vessel width and depth, blood flow, and attenuation. Vessel dimensions at baseline were verified by a blinded observer. Clinical improvement was detected as good, moderate, or none, and adverse effects were registered at 1-month follow-up.

RESULTS

In total, 14 patients with facial telangiectasia were included. At baseline, vessel width was median 0.25 mm (interquartile range [IQR]: 0.19-0.34 mm) with an intra-class coefficient (ICC) of 0.89 (95% confidence interval [CI]: 0.70; 0.97). Vessel depth was 0.30 mm (IQR: 0.25-0.33 mm; ICC: 0.40 [CI: -0.07; 0.75]). Vessel depth increased significantly from baseline to 1-month follow-up (P = 0.008), whereas no significant changes in vessel width, blood flow, or attenuation were detected. Clinical efficacy seemed related to the relation between vessel dimensions and applied energy settings.

CONCLUSIONS

The D-OCT imaging technique demonstrated that facial telangiectasias were found deeper within the skin after one IPL treatment. By characterizing the vessel dimensions and blood flow of telangiectasia, D-OCT may improve efficacy and safety of IPL. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Evaluating the Risk Factors of Post Inflammatory Hyperpigmentation Complications with Nd-YAG Laser Toning Using LASSO-Based Algorithm

The neodymium-doped yttrium aluminum garnet (Nd-YAG) laser is used for removal of pigmented skin patches and rejuvenation of skin. However, complications such as hyperpigmentation, hypopigmentation, and petechiae can occur after frequent treatments. Therefore, identifying the risk factors for such complications is important. The development of a multivariable logistic regression model with least absolute shrinkage and selection operator (LASSO) is needed to provide valid predictions about the incidence of post inflammatory hyperpigmentation complication probability (PIHCP) among patients treated with Nd-YAG laser toning. A total of 125 female patients undergoing laser toning therapy between January 2014 and January 2016 were examined for post-inflammatory hyperpigmentation (PIH) complications. Factor analysis was performed using 15 potential predictive risk factors of PIH determined by a physician. The LASSO algorithm with cross-validation was used to select the optimal number of predictive risk factors from the potential factors for a multivariate logistic regression PIH complication model. The optimal number of predictive risk factors for the model was five: immediate endpoints of laser (IEL), α-hydroxy acid (AHA) peels, Fitzpatrick skin phototype (FSPT), acne, and melasma. The area under the receiver operating characteristic curve (AUC) was 0.79 (95% CI, 0.70–0.88) in the optimal model. The overall performance of the LASSO-based PIHCP model was satisfactory based on the AUC, Omnibus, Nagelkerke R2, and Hosmer–Lemeshow tests. This predictive risk factor model is useful to further optimize laser toning treatment related to PIH. The LASSO-based PIHCP model could be useful for decision-making.

Thermohydrogel Containing Melanin for Photothermal Cancer Therapy

Melanin is an effective absorber of light and can extend to near infrared (NIR) regions. In this study, a natural melanin is presented as a photothermal therapeutic agent (PTA) because it provides a good photothermal conversion efficiency, shows biodegradability, and does not induce long-term toxicity during retention in vivo. Poloxamer solution containing melanin (Pol-Mel) does not show any precipitation and shows sol-gel transition at body temperature. After irradiation from 808 nm NIR laser at 1.5 W cm^-2 for 3 min, the photothermal conversion efficiency of Pol-Mel is enough to kill cancer cells in vitro and in vivo. The tumor growth of mice bearing CT26 tumors treated with Pol-Mel injection and laser irradiation is suppressed completely without recurrence postirradiation. All these results indicate that Pol-Mel can become an attractive PTA for photothermal cancer therapy.