Picosecond alexandrite laser treatment of nevus of Ota in children.

BACKGROUND: The picosecond alexandrite laser has been safely and effectively used to treat the nevus of Ota in adults. However, limited data are available for children. OBJECTIVE: To investigate the efficacy, safety, and correlative influencing factors of a 755nm picosecond alexandrite laser in the treatment of nevus of Ota in children. METHODS: We retrospectively analyzed Chinese children with nevus of Ota who received a 755nm picosecond alexandrite laser treatment in a tertiary dermatological hospital. RESULT: A total of 305 pediatric patients received an average of two treatments achieving an average of 79% pigment clearance. After the first treatment, 22 patients achieved complete clearance (95%-100%), and 72 patients achieved excellent response (75%-94%), with an average initial efficacy of 63% lesion clearance. Treatment at an early age achieved better initial efficacy (0- to 12-month group >1- to 6-year group, 6- to 12-year group). And 0- to 12-month group achieved better final efficacy. More treatment sessions also increased the final efficacy. Both initial efficacy and final efficacy were better when treating a darker lesion. The incidence of complications was 12.1%, with 10.8% being post-inflammatory hyperpigmentation and 1.3% being hypopigmentation. The rate of recurrence was 6.6%. LIMITATION: Retrospective study. CONCLUSION: A 755nm picosecond alexandrite laser is safe and effective in treating nevus of Ota in children. Younger to initiate treatment, darker lesions, and more treatments are positively associated with better pigmentation clearance.

Advancements in Laser Therapies for Dermal Hyperpigmentation in Skin of Color: A Comprehensive Literature Review and Experience of Sequential Laser Treatments in a Cohort of 122 Indian Patients.

The heightened awareness of ethnic dermatology aligns with the growing prevalence of skin of color communities globally, where hyperpigmentation disorders pose a common dermatological challenge. Effectively addressing dermal pigmentation is challenging due to its resistance to conventional therapies and its association with impaired quality of life. This underscores the need for effective treatments and a thorough grasp of laser advancements. A relevant literature search spanning the last 7 years across the PubMed database reveals core studies, challenges, and the evolution of laser technologies tailored for various forms of congenital and acquired dermal hyperpigmentation in skin of color. This comprehensive review explores the mechanisms, applications, and recommendations for pigmentary laser technologies, highlighting the key role of Q-switched lasers in their established millisecond/ nanosecond forms and emerging picosecond lasers, fractional non-ablative and ablative lasers, Intense Pulsed Light, etc. The summary of evidence includes studies on dermal melanocytosis (nevus of Ota and Hori's nevus), tattoos, acquired dermal macular hyperpigmentation, etc., and also entities with mixed epidermal-dermal components, such as melasma and post-inflammatory hyperpigmentation. The review offers valuable insights for clinicians to make informed decisions based on diagnosis, skin type, and the latest technologies to optimize results and minimize complications, especially in darker Fitzpatrick skin types. In their five-year study with 122 Indian patients, the authors applied specific laser combinations for diverse dermal melanoses, including tattoos, dermal/mixed melasma, acquired dermal macular hyperpigmentation, and dermal nevi. Substantial pigmentation reduction, subjectively assessed by both physicians and patients, was observed across all groups. A one-way ANOVA indicated a significant difference in mean improvement scores across various pigmentary conditions (F = 3.39, p = 0.02), with melasma patients exhibiting a significantly higher improvement score than tattoos (p = 0.03). The results affirmed the safety and efficacy of sequential laser therapy for dermal pigmentation in skin of color, advocating for flexibility in approach while maintaining the rationale behind the laser sequences. Despite advancements, challenges persist, and gaps in the current literature are identified. In conclusion, this summary highlights the ongoing pursuit of optimal protocols in dermatological laser treatments for dermal melanoses, offering valuable insights for future research and clinical practice.

Results and Follow-Up of a Sequential Q-Switched Laser Therapy for Nevus of Ota in Infants.

Background and Aim: There is a dearth of scholarly investigation pertaining to the effectiveness and safety of laser therapy for nevus of Ota manifestation in infants. The objective of this study is to examine the efficacy and safety of administering laser therapy at an early stage to treat nevus of Ota in infants. Methods: A total of 102 infants below the age of one who had nevus of Ota were treated at the Laser Center at Hangzhou Third People's Hospital. The treatment approach involved a combination of the Q-switched laser (with a wavelength of 755 nm) and the Q-switched laser (with a wavelength of 1064 nm). The treatment sessions were conducted at six-month intervals. Prior to and after each session, photographs and relevant parameters were documented, including any skin reactions. Subsequent follow-up was conducted through phone calls, WeChat, and text messages, and the parents/guardians of the infants completed a general questionnaire as well as Conner's Abbreviated Symptom Questionnaire. Results: Laser therapy exhibited significant efficacy in the treatment of nevus of Ota in infants. Success rates reached 88.7% after four sessions and 99.3% after seven sessions. No instances of serious adverse reactions, except for pain, were reported. Among the 47 infants subject to follow-up, 14 experienced a recurrence, resulting in a recurrence rate of 29.8%. Factors contributing to these recurrences included lesion size, subtypes, exposure to the sun, and location. Subsequent laser treatments, typically involving two to three additional sessions, proved effective in mitigating recurrences. Notably, none of the infants exhibited any signs of fear, anxiety, or other psychological abnormalities following laser therapy, and the overall satisfaction rate was markedly high. Conclusion: Commencing laser therapy promptly for nevus of Ota in infants is recommended. This early intervention significantly contributes to the overall well-being of infants, addressing both physical and psychological aspects.

Concurrent Occurrence of Trichilemmal Cyst and Nevus of Ota: Case Series.

Nevus of Ota or congenital oculodermal melanosis (ODM) is characterized by brown or blue/gray asymptomatic brown or blue/gray flat lesions of the skin, mucosae, episcleral/sclera, and uvea, which are located near the trigeminal nerve's ophthalmic and mandibular branches. The main ophthalmic complications are glaucoma and predisposition to uveal melanoma. "trichilemmal cyst" is also known as "wen" "pilar cyst" or " isthmus catagen cyst". It occurs in the scalp and mimics sebaceous cysts clinically. The swelling appears smooth in outline and is filled with cytokeratin. An unusual case of a 32-year-old male with both trichilemmal cyst and nevus of Ota, a 27-year-old female, and a 47-year-old male with nevus of Ota is discussed here.

Exploring the potential of intradermal platelet-rich plasma in treating acquired bilateral nevus of Ota-like macule (Hori's nevus): A pilot study.

BACKGROUND: Hori's nevus is a common and challenging dermatological condition, often complicated by post-inflammatory hyperpigmentation following treatment. Platelet-rich plasma (PRP) has demonstrated efficacy in the treatment of hyperpigmentation disorders such as melasma and periorbital darkening. Given the benefits and minimally invasive nature of PRP treatments, exploring its application in managing Hori's nevus through further investigation is worthwhile. AIMS: To evaluate the safety and effectiveness of intradermal PRP therapy for the treatment of Hori's nevus. METHODS: Ten female patients received bilateral intradermal PRP injections every 2 weeks for a total of four treatments. The modified dermal pigmentation and severity index (mDPASI), mean melanin index (MI), brightening score, patient self-assessment, and clinical photographs were evaluated at 2, 4, 8, and 12 weeks post-treatment. Adverse events were also recorded to determine treatment safety. RESULTS: At 12 weeks post-treatment, mDPASI decreased 38.86%, from 0.929 ± 0.617 to 0.568 ± 0.415 (p < 0.05). The mean melanin index decreased 12.75%, from 208.650 ± 26.319 to 182.052 ± 17.028 (p < 0.05). In addition, the mean brightness score evaluated by two experts was 1.4, indicating 25-50% improvement. At the end of the study, 50% of the patients reported 50-75% improvement. Side effects included pain, mild edema, and bruising, which resolved spontaneously within 3 days. No serious side effects were found. CONCLUSION: Our results suggest that intradermal PRP therapy may be a safe and effective alternative for the treatment of Hori's nevus and can complement conventional interventions. However, further research with a larger sample size, control groups, and longer follow-up is needed to confirm these findings.

A retrospective study of 1064-nm Q-switched Nd:YAG laser therapy for acquired bilateral nevus of Ota-like macules.

BACKGROUND: The therapeutic efficacy of laser treatments for acquired bilateral nevus of Ota-like macules (ABNOM) varies among studies, and few studies have evaluated the factors affecting therapeutic effects. AIMS: To evaluate the efficacy and safety of 1064-nm Q-switched Nd:YAG laser (QSNYL) therapy for ABNOM and to identify the factors influencing the outcome. METHODS: A total of 110 patients with ABNOM were retrospectively evaluated and received two-to-nine treatment sessions. The effects of different factors on the therapeutic effect were analyzed on the basis of the number of treatments, age at first treatment, skin type, lesion color, affected area, number of lesion sites, and presence of concomitant melasma. RESULTS: The curative effect was positively correlated with the treatment time and negatively correlated with the increasing age at first treatment (p < 0.05). The curative effect was better in patients with skin type III than those with type IV ( p < 0.05) and in patients with a lesion area of less than 10 cm2 than those with a larger affected area (p < 0.05). Additionally, the treatment effect was poorer in patients with concomitant melasma (p < 0.05). The treatment effect was not significantly correlated with the lesion color or number of affected sites (p > 0.05). Eleven patients (10%) developed postinflammatory hyperpigmentation (PIH). CONCLUSIONS: Early and repeated QSNYL therapy achieved satisfactory results for ABNOM. The risk of PIH after laser treatment is highest among patients with older age, darker lesion color, and darker skin color. For patients with ABNOM with concurrent melasma, low-energy laser therapy is recommended to reduce the risk of melasma aggravation.

Blue Nevus Hidden within the Nevus of Ota.

A 3-year-old boy presented with bluish patch and scattered blue spots on the left side of his face. After several sessions of laser treatment, the azury patch in the periorbital area became even darker. Histopathology showed many bipolar, pigment-laden dendritic cells scattered in the papillary and upper reticular dermis. Immunohistochemically, these cells were positive for S100, SOX-10, melan-A, P16, and HMB-45. The positive rate of Ki-67 was less than 5%. Finally, the lesion was diagnosed with nevus of Ota concurrent with common blue nevus. Therefore, for cases of the nevus of Ota with poor response to laser treatment, the possible coexisting diseases should be suspected.

Prospective comparison study of a 550 picosecond 755 nm laser vs a 50 ns 755 nm laser in the treatment of nevus of Ota.

Since the introduction of selective photothermolysis, Q-switched nanosecond lasers have been used for the treatment of dermal pigmented lesions. Over the past several years, picosecond lasers have been introduced to the cosmetic community. We recently performed a study comparing a 550 picosecond 755 nm laser versus a 50 ns 755 nm laser, with the purpose of evaluating the clinical efficacy and complications of each laser when treating nevus of Ota. Ten Asian patients with nevus of Ota were enrolled in the study. Each lesion was split into 2 parts, and patients were treated with a 755 nm picosecond laser (PSL) and a 755 nm nanosecond laser (NSL). The clinical endpoint for fluence choice was immediate whitening (PSL: 2.33 ~ 3.36 J/cm2, NSL: 5.5 ~ 7 J/cm2) of the treated area. The pulse duration was fixed at 550 picoseconds (PSL) and 50 ns (NSL). The spot size of each laser was 2.5-3 mm. Laser treatments were performed until excellent clinical improvement was observed. Patients were examined 1 week after the first treatment, at each follow-up visit, and 6 months after the last laser treatment. The average number of treatment sessions to achieve excellent clinical improvement was 4.2 treatments using PSL and 5.4 treatments using NSL. One case of hyperpigmentation and one case of hypopigmentation were observed in the NSL treatment group. There were no complications in the PSL treatment group. The 755 nm 550 picosecond laser is significantly more effective than the 755 nm 50 ns laser in the treatment of nevus of Ota. The PSL treatment group also had minimum side effects.

Nevo de Ota bilateral: presentación de un caso de distribución poco frecuente / Bilateral nevus of Ota: an unusual presentation

RESUMEN El Nevo de Ota, es una melanocitosis dérmica que se desarrolla por un defecto embrionario en la migración de los melanocitos desde la cresta neural a la piel y mucosas. Presentamos una paciente de 32 años, con Nevo de Ota bilateral de presentación infrecuente.

ABSTRACT Nevus of Ota is a dermal melanocytosis that develops due to an embryonic defect in the migration of melanocytes from the neural crest to the skin and mucous membranes. We report a 32-year-old female patient with a bilateral nevus of Ota with a rare manifestation due to its unusual distribution.

An update on ophthalmological perspectives in oculodermal melanocytosis (Nevus of Ota).

PURPOSE: To provide a review of the literature on oculodermal melanocytosis (ODM) with a focus on the diagnostic and therapeutic implications of multimodal imaging techniques in the management of ophthalmic complications. METHODS: The authors carried out a literature search on PubMed, Medline, and Scopus of English language articles published on ODM through August 2021. This review presents traditional and novel diagnostic methods in the diagnosis and follow-up of patients with particular emphasis on addressing the role of imaging in the management of the ophthalmic complications of the condition towards improving current practice patterns. RESULTS: ODM is a rare, prevalently unilateral, congenital condition that presents with brown or blue/gray flat asymptomatic lesions of the skin, mucosae, episclera/sclera, and uvea localized within the territory of distribution of the ophthalmic and mandibular branches of the trigeminal nerve. Glaucoma and predisposition to uveal melanoma are the main ophthalmic complications. Diagnosis and management are through comprehensive opthalmological examination and traditional imaging methods such as ultrasonography and fluorescein/indocyanine green angiography as pigmentation of the fundus can conceal subtle retinal and choroidal alterations. Anterior segment optical coherence tomography and ultrasound biomicroscopy are used to evaluate the anterior segment and the ciliary body in the presence of glaucoma or melanoma of the anterior uveal tract. Fundus autofluorescence and retinal pigment epithelium (RPE) alterations are of aid in the differential diagnosis between choroidal nevi and melanoma. Enhanced depth imaging spectral domain optical coherence tomography offers outstanding in vivo evaluation of the dimensions and details of tumors or nevi and surrounding choroidal tissues and small choroidal melanomas may show distortions of the retinal and sub-retinal profile, presence of intra and sub-retinal fluid, abnormalities of the RPE, and compression of the choriocapillaris. CONCLUSIONS: Novel multimodal imaging techniques are significant in the diagnosis and management of the ophthalmic complications of ODM. Fundus autofluorescence and enhanced depth spectral domain optical coherence tomography have adjunctive value in the detection of early-stage melanoma and differential diagnosis between nevi and melanoma. Awareness of current and emerging imaging techniques can propagate improved standardized definition and assessment of the complications of ODM.

Treatment of Nevus of Ota in Black patients with the 1064 nm QS or picosecond laser and nonablative fractional photothermolysis.

OBJECTIVES: Nevus of Ota is a benign melanocytic lesion that presents as a unilateral blue gray to brown facial patch favoring the distribution of the first two branches of the trigeminal nerve. Incidence is highest in Asian and Black populations, however, the overwhelming majority of studies are limited to diagnosis and treatment in Asian patients. We herein present 10 Black patients with Fitzpatrick skin types (FST) V and VI who underwent laser treatment for Nevus of Ota. METHODS: We performed a retrospective review of Black patients presenting with Nevus of Ota. Race was self-designated by all patients and documented in the medical record at the time of initial consultation. Primary outcomes were based on improvement using before and after photographs which were graded by three independent board-certified dermatologists using a 5-point visual analog scale. RESULTS: Ten FST V or VI patients with an age range of 9 months to 45 years were treated for Nevus of Ota. All patients were treated with the 1064 nm Q-switched neodymium doped yttrium aluminum garnet (QS Nd:YAG) and on average received 4.7 treatments at 2-10 month intervals. Fluence ranged from 1.8 to 2.3 J/cm2 , and total pulse count ranged from 510.9 to 776.6. 2/10 patients were additionally treated with 1550 nm nonablative fractional resurfacing (NAFR), and 1/10 patients underwent combination therapy with both NAFR and 1064 nm picosecond laser therapy. Overall, patients saw a mean improvement of 51%-75% at follow-up 5-254 weeks (mean 51.5 weeks) after treatment. Three patients experienced mild guttate hypopigmentation in treated areas. No other long-term adverse events were encountered. CONCLUSION: 1064 nm QS Nd:YAG laser therapy is a safe and efficacious treatment for Nevus of Ota in patients with FST V and VI. When patient improvement plateaus, combining therapy with 1550 nm NAFR or transitioning to 1064 nm picosecond laser may be of benefit. Patients should be counseled on the risk of guttate hypopigmentation. This is the largest case series to date of Black patients with Nevus of Ota, highlighting the need for further investigation to determine optimal device settings and treatment parameters for this population.

Blue Nevus Hidden within the Nevus of Ota / 中国医学科学杂志(英文版)

A 3-year-old boy presented with bluish patch and scattered blue spots on the left side of his face. After several sessions of laser treatment, the azury patch in the periorbital area became even darker. Histopathology showed many bipolar, pigment-laden dendritic cells scattered in the papillary and upper reticular dermis. Immunohistochemically, these cells were positive for S100, SOX-10, melan-A, P16, and HMB-45. The positive rate of Ki-67 was less than 5%. Finally, the lesion was diagnosed with nevus of Ota concurrent with common blue nevus. Therefore, for cases of the nevus of Ota with poor response to laser treatment, the possible coexisting diseases should be suspected.

Nevus of Ota: Combination Treatment with Q-Switched Neodymium-Doped Yttrium Aluminum Garnet Laser and Fractional CO2 Laser.

Background: Nevus of Ota is a facial dermal melanocytic hamartoma occurring more commonly in Asians. The mainstay of treatment is 1064-nm Q-Switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, which has shown variable results in pigmented skin. Objective: The aim of this study was to determine whether Q-Switched Nd:YAG laser treatment combined with fractional CO2 laser is more efficacious than Q-Switched Nd:YAG laser alone. Materials and Methods: This was a prospective study with 81 patients. The patients were randomly divided into two groups. Group 1 received 1064-nm Q-Switched Nd:YAG laser alone and group 2 in addition received a fractional CO2 laser as well. Both groups received six sittings at monthly intervals. The treatment response was documented with physician global assessment (PGA) and patient's treatment satisfaction on Wong-Baker Facial Pain Scale (WBFPS). Dermoscopic evaluation was done to see subsurface pigment clearance. Results: In the combination group, 25% of patients had more than 50% improvement as compared with 5.71% in group 1. To achieve a mean PGA score of 1.4, it took six sessions for group 1 versus only four for group 2. Dermoscopic evaluation showed faster pigment clearance in the combination group. Conclusion: Combining two lasers shows statistically significant faster and greater degree of improvement as compared with Q-Switched Nd:YAG laser monotherapy in nevus of Ota.

The risk of glaucoma associated with phacomatosis cesioflammea and phacomatosis cesioflammeo-marmorata

Background: The ocular features of phacomatosis pigmentovascularis (PPV) have rarely been reported, and glaucoma is the leading cause of blindness in patients with this condition. To protect vision in these patients, it is important to identify glaucoma as early as possible. Objectives: To systematically report the systemic and ocular manifestations of phacomatosis cesioflammea and phacomatosis cesioflammeo-marmorata, and to investigate a glaucoma risk scoring system. Materials & Methods: In this prospective study, patients with PPV from 2014 to 2021 were included. Clinical information was collected, and associations with glaucoma were evaluated. The suitability of the scoring system was assessed. A systematic literature review and analysis of reported cases of PPV was performed. Results: A total of 28 participants with PPV were included. Their ocular findings were similar, ranging from episcleral hyperpigmentation (78.5%), glaucoma (75%), choroid haemangioma (38%), and retinal vascular abnormalities (48%), to hyperpigmentation of the cornea, iris, lens and fundus. Glaucoma was associated with multiple factors, especially a thick choroid (odds ratio: 2.61; p = 0.008) and a diffuse mass-type of episcleral hyperpigmentation (odds ratio: 41.3; p = 0.027). The risk scoring system was characterized by high sensitivity (84%) and specificity (80%; AUC = 0.91) in predicting glaucoma. Conclusion: In addition to involving the systemic system, phacomatosis cesioflammea and phacomatosis cesioflammeo-marmorata also represent a specific spectrum of ophthalmic vascular malformations and hyperpigmentation. Early and periodic detailed ocular examination are recommended. The novel scoring system will help to tailor follow-up for visual protection.

Aiming to personalized laser therapy for nevus of Ota: melanin distribution dependent parameter optimization.

Aiming to the personalized laser therapy of nevus of Ota (NO), a local thermal non-equilibrium model was employed to optimize laser wavelength, pulse duration, and energy density under different melanin depth and volume fraction. According to our simulation, the optimal pulse duration is between 15 and 150 ns to limit heat transfer inside the hyperplastic melanin, and 50 ns is recommended to decrease the energy absorption by normal melanin in epidermis. Correlations of the minimum and the maximum energy densities are proposed with respect to melanin depth and volume fraction for the 755-nm and 1064-nm lasers. For the same NO type, the therapy window of the 755-nm laser is larger than that of 1064-nm. For NO with shallow depth or low volume fraction, the 755-nm laser is recommended to make the treatment more stable owing to its lager therapy window. For deeper depth or higher volume fraction, the 1064-nm laser is recommended to avoid thermal damage of epidermis. Through comparison with clinical data, the optimized laser parameters are proved practicable since high cure rate can be achieved when energy density falls into the range of predicted therapy window. With developing of non-invasive measurement technology of melanin content and distribution, personalized treatment of NO maybe possible in the near future.

Nevus of Ota on the auricle successfully treated with Q-switched ruby laser.

Nevus of Ota is a dermal melanocytosis that consists of blue-brown spots, patches and plaques along the distribution of the first and second branches of trigeminal nerve. The efficacy of Q-switched ruby laser treatment against nevus of Ota on dark skin has not been described. The present case, a 2-month-old Indonesian girl, showed rare auricular involvement. Because ear has complicated steric structure, whose skin is sensitive and thin, pain and inflammatory reaction are inevitable. We discussed the difficulty of laser treatments on auricular lesions.

Laser Surgery for Dermatologic Conditions in Pediatric Patients.

Laser therapy is an effective treatment that can be used in a wide range of cutaneous conditions in pediatric dermatology. It is an important tool to have in one's armamentarium. The parameters within each laser can vary greatly by the make and model of the laser, making it difficult to make settings generalizable. The goal of this article is to provide some general guiding principles for laser choice, theory behind laser parameter choice, and education surrounding tissue response which will guide treatment parameter changes.

Bilateral Phakomatosis Cesiomarmorata With Ocular Melanocytosis and Secondary Glaucoma.

Phakomatosis pigmentovascularis (PPV) is a family of rare congenital diseases where vascular malformation coexists with melanocytic, dermal, or ocular lesions. The cesiomarmorata type is even rarer, and most such cases are reported with unilateral occurrence. We present an atypical case of a patient with bilateral phakomatosis cesiomarmorata, bilateral ocular melanocytosis, and bilateral glaucoma. No malformation to resist aqueous drainage was identified. Long-term management of intraocular pressure (IOP) using topical antiglaucoma medication was successful. This case report refines the clinical presentation of phakomatosis cesiomarmorata and may help diagnose and treat future cases.

A Comparative Study of Dermatoscopic Features of Melasma and Hori's Nevus in Asian Patients.

Background: Dermatoscopy is a noninvasive diagnostic tool for pigmented lesions. However, data regarding dermatoscopic features in melasma and Hori's nevus, which are commonly found in Asian populations, are still lacking. In addition, melasma coexisting with Hori's nevus presents a particular diagnostic challenge and they generally require different treatments. Objective: We sought to describe the dermatoscopic features of melasma and Hori's nevus and to establish diagnostic clues for each condition. Methods: Fifty patients with melasma and 46 patients with Hori's nevus were enrolled in the study. Dermatoscopic pictures were taken with Dermlite DL200 HR (3Gen, San Juan Capistrano, Califorinia) and evaluated by two blinded board-certified dermatologists. Results: The dermatoscopic features more prominently seen in melasma compared to Hori's nevus include light brown pigmentation (98% vs. 10.9%, P<0.001), regular pigment network (38% vs. 2.2%, P<0.001), irregular pigment network (98% vs. 63%, P<0.001), arcuate structure (68% vs. 13%, P<0.001), circles (48% vs. 10.9%, P<0.001), sparing of follicles and sweat gland openings (98% vs. 4.3%, P<0.001), and telangiectasias (52% vs. 19.6%, P=0.001). In contrast, the common features of Hori's nevus include blue-brown or grey pigmentation (63% vs. 0%, P=0.001) and speckled homogenous pattern (52.2% vs. 0%, P<0.001). Conclusion: Dermatoscopy is a useful diagnostic tool for distinguishing between melasma and Hori's nevus. In patients with coexistence of both conditions, dermatoscopy can be used to confirm the diagnosis and aid the proper treatment.

Efficacy evaluation and treatment parameter optimization for laser surgery of Ota's nevus based on an advanced non-equilibrium bio-tissue heat transfer model.

This study was performed to better understand the laser-tissue interaction mechanism and optimize the laser wavelength and pulse duration for the laser treatment of Ota's nevus, thereby providing the precise theoretical guidance for clinician to improve the therapeutic effect. A non-equilibrium bio-tissue heat transfer model coupled with thermo-mechanical effect for the explosive vaporization of melanin granule induced by laser heating was developed to investigate the temperature and thermal damage distribution using alexandrite (755 nm) and Nd:YAG (1064 nm) lasers with the pulse width of 10-120 ns. Cryogen spray cooling (CSC) was introduced to prevent the epidermal thermal damage due to competitive laser absorption between epidermal and dermal melanin. Thermal injury of the epidermis with temperature in the melanin zone reaching 132.3 °C was induced by alexandrite laser. The optimal pulse durations were 50 and 30 ns, and the corresponding incident laser fluence thresholds were 6.45 and 19.5 J·cm-2 for alexandrite and Nd:YAG laser, respectively, with the pre-cooling of R32 spray. Using R32 spray cooling, the 1064-nm laser fluence threshold of melanin can be increased by 56.0%, resulting in an indirect increase (80.4%) of injury thickness. Nd:YAG laser (1064 nm) was highly suitable for the removal of melanin in the deep tissue owing to its deep penetration. Too short pulse duration should be avoided to prevent the epidermal thermal damage. The improvement of therapeutic effect by CSC demonstrates its high clinical application potential.