Med Lasers 2023; 12(1): 51-58  https://doi.org/10.25289/ML.23.003
Effectiveness of 250-picosecond laser for the treatment of melasma and pigmented lesions with a low fluence 1,064-nm Nd:YAG laser in Republic of Korea: retrospective study
Sun Jae Lee, Dong Gyu Kim, Seung Min Nam, Han Gyu Cha, Eun Soo Park
Department of Plastic and Reconstructive Surgery, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Republic of Korea
Correspondence to: Eun Soo Park
E-mail: peunsoo@schmc.ac.kr
ORCID: https://orcid.org/0000-0003-2966-9122
Received: February 1, 2023; Accepted: February 13, 2023; Published online: March 31, 2023.
© Korean Society for Laser Medicine and Surgery. All rights reserved.

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background and Objectives: Melasma is a pigment disease mainly acquired by skin exposed to sunlight. Picosecond laser was developed for a treatment that is more effective than Q-switch laser in tattoo treatment and can reduce complications. This study was undertaken to confirm the efficacy of a 250 picosecond laser in melasma and pigmented lesion therapy.
Materials and Methods: The study is a retrospective analysis of melasma and pigmented lesion cases treated from April 2022 to September 2022 using the 250 picosecond 1,064 nm laser. Data before and after treatment were compared for patients who had undergone picosecond lasers toning mode up to five times. A clinical picture of the patient was taken using skin analysis program, and quantitative values for skin pigment and skin tone were obtained.
Results: A total of 87 patients were included in the study. Results of the paired-sample t-test comparing the difference in polarized light and ultraviolet pigmentation in entirety and for each part showed a decrease in the mean score. Analysis of skin tone revealed that a higher score showed better results. The mean score of skin tone increased statistically significantly.
Conclusion: Our results confirmed that the 250 picosecond laser is effective in treating melasma and pigmented lesions. In particular, our study used a skin analysis tool program to add objectivity and confirmed the statistical significance of the results.
Keywords: Pico toning; Picolasers; Laser therapy; Pigmentation; Melanosis
INTRODUCTION

Melasma is a common cosmetic pigmentary disorder that manifests as symmetrically distributed, irregular, light to dark brown macules on the face. Although the exact causes of melasma have not been fully elucidated yet, it is widely recognized that extensive ultraviolet (UV) light exposure [1], hormonal disorders [2,3], and genetic susceptibility [4] play important roles in its pathogenesis. It usually occurs on the face and rarely occurs in other areas. To treat melasma, laser, and other treatment methods are used in parallel. Among treatments other than laser, sunscreens to block UV light and topical anti-melanogenesis agents including hydroquinone, retinoic acid, glycolic acid, and corticosteroid are commonly used for treating melasma [5,6].

Recently, laser-based treatment of hyperpigmentation conditions of the skin including melasma has been proposed as an adjunctive treatment [7]. The main mechanism in the treatment of pigmentation using a laser is that photothermal energy can target the melanin pigment to cause “selective photothermolysis” [8]. Lasers widely used in the treatment of pigmented skin include Q-switch ruby laser, Q-switch alexandrite laser, and Q-switch Nd:YAG laser [9,10]. However, none of these laser treatments is consistently effective enough to become the gold standard, and complications including pain, erythema, and post-inflammatory hyperpigmentation or hypopigmentation are frequently reported [10,11].

Picosecond laser was developed for a treatment that is more effective than Q-switch laser in tattoo treatment and can reduce complications. A picosecond laser uses extremely short pulse duration (that is, 450-750 picosecond pulse duration) to deliver higher energies with a lower photothermal effect than other laser technologies with a longer pulse duration range. As a result, it has the advantage of minimizing post-procedure pain and skin discoloration after laser treatment [12]. In addition, a picosecond laser can cause more melanin fragmentation with a higher energy than a nanosecond laser [13]. Therefore, when using a picosecond laser, tattoo and facial acne scar lesions can be treated with low fluence and satisfactory results can be obtained with minimal side effects [14,15].

The lower the picosecond can be used in the picosecond laser, the better the effect can be expected, so it will be more meaningful to develop the picosecond laser with a lower picosecond. Under the concept of stress relaxation time (SRT), as the pulse duration approaches true picosecond, the photothermal effect becomes weaker and more photomechanical effects occur. Even when tattoo is removed, the crushing rate of tattoo pigment particles varies depending on the wavelength. Although the absorbed amount is similar, a shorter pulse duration will lead to a higher crushing rate. After all, a 450-picosecond laser is more effective in tattoo removal than a 750-picosecond laser. The higher the crushing rate, the smaller the tattoo pigment particles. Smaller pigment particles can be easily eaten by macrophages and quickly excreted through the lymphatic system. Therefore, pulse duration is a very important factor in tattoo removal.

By applying this principle to melasma, the objective of this study was to determine whether a lower picosecond laser could be more effective in treating melasma. In this study, we tried to determine the effectiveness of a 250-picosecond laser in treating melasma.

METHODS
Ethics statement: This retrospective study was approved by the Institutional Review Board (IRB) of Soonchunhyang University Bucheon Hospital (IRB no. 2022-10-015) and performed in accordance with the Declaration of Helsinki. A written informed consent was obtained from the patient for the publication of the study.

Subjects and study design

This study performed a retrospective analysis of cases treated using a 250-picosecond 1,064-nm laser for patients diagnosed with melasma or pigmentation from April 2022 to September 2022. A total of 87 patients with melasma or pigmentation were treated with the laser. Through patient's chart review, we obtained patient's basic personal information. Patients with underlying skin disease, those with immunodeficiency, those who were taking hormone replacement therapy, those who were currently pregnant, and those who were breastfeeding were excluded from this study. Patients who had been treated with topical agents (such as retinoid, corticosteroid, and hydroquinone) within one month were also excluded from the study.

Photographs were taken immediately before the patient started laser treatment and at each visit. Photographic images were obtained under the same condition. For digital pigmentation analysis, we used a Mark-Vu skin analysis system (PSI Plus). The Mark-Vu system has four different light emitting diode-type light sources (normal, specular, polarized, UV), a complementary metal–oxide–semiconductor sensor of 18.0 mega pixels, and integrated analysis tools. Two-dimensional images of the whole face were taken in a natural manner (right lateral, right lateral 45°, central, left lateral 45°, left lateral).

Laser treatment

A picosecond Nd:YAG laser device, Picocare Majesty (WONTECH) was used in this study. The use of a topical anesthetic agent for pain relief (EMLA®, Recipharm Karlskoga AB) was applied only when the patient complained of pain or needed it. However, except in very few cases, basically no pain-reducing ointment was used.

Picocare Majesty laser treatment was performed at a wavelength of 1,064 nm, 7-10 mm spot size, 0.1-0.6 J/cm2 fluence, 10 Hz frequency, and 2,000-3,500 shots for full face (Table 1).

Table 1 . Laser parameter

Wavelength (nm)Spot size (mm)Fluence (J/cm2)Frequency (Hz)Total shots
1,06470.1-0.6102,000-3,500


Evaluation

To objectively confirm the effect of melasma treatment, we used the skin analysis program (Mark-Vu).

The Mark-Vu analyzer utilizes focused area analysis to optically quantify the degree of pigmentation and melanin amount of specific areas (Fig. 1) and show a numerical value along the areas. Data were recorded and analyzed pre- and posttreatment. Measurement of skin color is an accepted method of assessing melanin content and pigmentation levels. Additionally, digital images of the targeted area under natural and polarized, UV light were also taken at the same time points.

Figure 1. Positions of each part of items (A, B, E, F, G, H) and numerical values on polarized light before and after treatment.

At each visit, Mark-Vu photograph was taken after washing the face before laser treatment. Only photographs of patients who had undergone a maximum of five laser treatments were used for analysis. After taking a picture of the patient with Mark-Vu, analysis value from the skin analysis program was used. Among them, pigmentation was obtained by analyzing pigmentation values under natural light and UV light, respectively. The higher the pigmentation score, the higher the pigmentation score. Conversely, in the skin tone analysis, the skin tone score increased as the skin tone improved. These numerical values were obtained by averaging the entire face and by subdividing each part of the face. A is the forehead, B is the nose and bridge of the nose, E is the right under eye area, F is the left under eye area, G is the right malar area, and H is the left malar area (Fig. 1).

Two weeks after the last procedure, patient’s satisfaction with the treatment was evaluated. Subject satisfaction was evaluated on a 5-point Likert scale questionnaire (1 = very unsatisfied, 2 = unsatisfied, 3 = neutral, 4 = satisfied, 5 = very satisfied).

All adverse events and complications, including erythema, edema, bullae, post-inflammatory hyperpigmentation, and hypopigmentation, on medical records were reviewed during treatment and visitation.

Statistical analysis

Statistical analysis was performed using a paired-sample t-test. In the case of pigmentation, it showed a small but statistically significant improvement. In particular, by analyzing scores of the entire face and each part, we were able to determine which part had more effectiveness. In the case of skin tone, an increase in score meant an improvement. It was determined whether the improvement was statistically significant. Patient satisfaction survey results were also analyzed using a paired-sample t-test to determine whether statistically significant results were obtained.

RESULTS

A total of 87 patients were included in this study. Of them, 97.7% were females. As for the distribution by age group, those in their 20s, 30s, 40s, and 50s accounted for 12.6%, 36.8%, 39.1%, and 11.5%, respectively, with those in their 40s having the highest percentage (Table 2).

Table 2 . Subject demograhpics

DemographicsValue
Total no. of patients87 (100)
Sex
Male2 (2.3)
Female85 (97.7)
Age (yr)39.45 ± 8.14
20s11 (12.6)
30s32 (36.8)
40s34 (39.1)
50s10 (11.5)
Treatment laser session (minimum 3-maximum 5)
567 (77.0)
413 (14.9)
37 (8.1)

Values are presented as number (%) or mean ± standard deviation.



As a result of paired-sample t-test, when comparing the difference in polarized light (PL) pigmentation for the whole part and for each part, the mean was decreased from 22.38 to 20.02 (p < 0.05). When different parts were compared, PL pigmentation was decreased from 17.52 to 15.47 in the A area (p < 0.05), from 32.60 to 31.34 in the B area (p < 0.05), from 19.16 to 17.24 in E and F areas (p < 0.05), and from 22.82 to 19.58 in G and H areas (p < 0.05). Pigmentation was found to be decreased in all areas (Table 3, Figs. 1, 2).

Table 3 . Differences in pre- and post-procedure polarized light pigmentation by whole face and region

By partProcedureMean ± standard deviationt(p)
Full facePre22.38 ± 7.095.05 (<0.001***)
Post20.02 ± 5.61
APre17.52 ± 8.043.82 (<0.001***)
Post15.47 ± 6.37
BPre32.60 ± 9.332.27 (0.013*)
Post31.34 ± 8.13
E, FPre19.16 ± 6.864.36 (<0.001***)
Post17.24 ± 5.65
G, HPre22.82 ± 10.693.41 (<0.001***)
Post19.58 ± 6.96

The total number of patients is 87.

*p < 0.05, ***p < 0.001.


Figure 2. Differences in pre- and post-procedure polarized light pigmentation by whole face and region graph.

When comparing differences in UV pigmentation by the same area using the same analysis method, the mean was decreased from 22.10 to 20.06 (p < 0.05). It was decreased from 17.84 to 16.24 in the A area (p < 0.05), from 30.01 to 27.68 in the B area (p < 0.05), from 22.06 to 19.86 in E and F areas (p < 0.05), and from 20.26 to 18.17 in G and H areas (p < 0.05). Thus, UV pigmentation values were also decreased in all areas (Table 4, Fig. 3).

Table 4 . Differences in ultraviolet pigmentation by whole and area before and after treatment

By partTreatmentMean ± standard deviationt(p)
Full faceBefore22.10 ± 7.144.34 (<0.001***)
After20.06 ± 5.69
ABefore17.84 ± 7.573.30 (<0.001***)
After16.24 ± 6.42
BBefore30.01 ± 11.723.48 (<0.001***)
After27.68 ± 9.02
E, FBefore22.06 ± 7.253.61 (<0.001***)
After19.86 ± 6.58
G, HBefore20.26 ± 8.622.99 (0.002**)
After18.17 ± 5.57

The total number of patients is 87.

**p < 0.01, ***p < 0.001.


Figure 3. Differences in ultraviolet pigmentation by whole and area before and after treatment graph.

Comparing the difference in skin tone, the mean was increasd from 55.57 to 55.91 (p < 0.05). Although it was increased from 55.83 to 55.87 in the A area, such increase was not statistically significant (p = 0.449). In the B area, it was increased from 55.94 to 55.98. Such increase was not statistically significant either (p = 0.426). In E and F areas, it was increased from 53.47 to 54.55 (p < 0.05). In G and H areas, it was decreased from 56.51 to 56.17 (p < 0.05). A statistically significant increase was shown in the mean and in E and F areas (Table 5, Fig. 4).

Table 5 . Differences in skin tone by whole and area before and after treatment

By partTreatmentMean ± standard deviationt(p)
Full faceBefore55.57 ± 3.26–1.83 (0.035*)
After55.91 ± 3.36
ABefore55.83 ± 5.06–0.13 (0.449)
After55.87 ± 5.10
BBefore55.94 ± 3.67–0.19 (0.426)
After55.98 ± 4.06
E, FBefore53.47 ± 4.43–4.26 (<0.001***)
After54.55 ± 5.16
G, HBefore56.51 ± 4.581.83 (0.035*)
After56.17 ± 5.04

The total number of patients is 87.

*p < 0.05, ***p < 0.001.


Figure 4. Differences in skin tone by whole and area before and after treatment graph.

When comparing satisfaction of patient’s pre- and post-procedure, the patients’ satisfaction about skin tone increased from 2.53 to 3.34 points (p < 0.05). Their satisfaction about pigmentation also increased from 2.36 points to 3.21 points (p < 0.05; Fig. 5). The photographic finding of a case before laser treatment and 2 weeks after five times laser treatment is presented (Figs. 6-8).

Figure 5. Patient’s satisfaction difference between pre- and post-procedure graph.
Figure 6. Photographic findings of pigmentation patient before and after 250 picosecond laser treatment (polarized light).
Figure 7. Photographic findings of pigmentation patient before and after 250 picosecond laser treatment (ultraviolet light).
Figure 8. Photographic findings of skin tone patient before and after 250 picosecond laser treatment.
DISCUSSION

In the treatment of melasma, laser treatment is a frequently used. However, there are many factors such as patient dissatisfaction affecting the treatment effect, making it difficult to establish a clear treatment. Melasma has always been recognized as an incurable disease because some parts might not show noticeable effects of treatments. The current medical level does not treat the cause of melasma. It only treats the phenomenon of melasma, the brown lesion in which melasma occurs. Laser can be used to treat skin lesions with an increased number of epidermal melanocytes or dermal melanocytes. However, it is difficult to treat with a laser if the function of cells is increased. For this reason, it is important to combine laser treatment and drug treatment in melasma treatment rather than worrying about which laser to treat melasma. The laser used for pigment lesions such as melasma has also been developed from the existing nanosecond laser to a picosecond laser. Picosecond lasers can treat lesions with 1/3 to 1/2 of the energy used in nanosecond lasers. Compared to nanosecond lasers, picosecond lasers have more photoacoustic effects and fewer photothermal effects [16,17]. Therefore, the risk of collateral damage to surrounding tissue is less.

The picosecond laser that was initially released is the PicoSure laser (CYNOSURE), which is a 755-nm alexandrite picosecond laser. However, in the treatment of melasma, the 1,064-nm wavelength, which is less absorbed by melanin, is more effective than the 755-nm wavelength. The 755-nm wavelength itself has high absorption of melanin, so it is more effective in treating pores, and in the treatment of melasma, the treatment effect may decrease because postinflammatory hyperpigmentation (PIH) occurs. Because, in pore treatment, fibrosis around the pores must be removed first. Since the 755-nm wavelength has higher absorption for melanin than the 1,064-nm wavelength in the follicular melanocyte present in the outer root sheath of hair, heat and this is because the microsubcision effect of the secondary target, fibrous tissue, by plasma is superior [18]. Most of picosecond lasers with 1,064-nm wavelength were composed of 450 picoseconds. The Picocare Majesty we used in this study applied 250 picoseconds at a wavelength of 1,064-nm. Thus, a shorter picosecond laser was used.

For SRT of 1 μm size melanosome, 250-picosecond laser is suitable for treating the lesion safely by destroying melanosome only without damaging surrounding tissue, the pulse duration should be shorter than 300-picosecond laser [19]. The thermal relaxation time for the 10-100 nm tattoo particles is 100-10 nanoseconds and more safe and effective treatment without thermal damage, the pulse duration needs to be shorter due to small sizes of tattoo particles. The excellent scar treatment and skin rejuvenation effects can be induced by forming laser-induced optical breakdown more effectively with a shorter pulse duration and a higher peak power.

Research on the treatment of melasma using lasers has continued for the past decade, especially in the treatment of melasma using Q-switched Nd:YAG laser [20-22]. In these studies, the treatment showed effective results. However, post-laser hyperpigmentation has occurred in several cases with frequent recurrence [23,24]. In a comparative study of split face treatment using a Q-switched Nd:YAG laser and a picosecond laser, picosecond laser showed faster and better melasma clearance rate [25]. Another study has reported that the use of hydroquinone cream treatment in combination with a 1,064-nm picosecond laser showed better results than using hydroquinone cream alone, and also proved the safety of using a 1,064-nm picosecond laser [26].

Lee et al. [27] have used Mark-Vu for patient skin analysis in a retrospective analysis of a microneedle patch triple combination cream and hyaluronic acid combination treatment for benign pigmented skin lesions. In the present study, we also used a Mark-Vu system, a skin analysis program that made the analysis of treatment effects more objective. It also made it impossible to intervene in numerical values.

Kim et al. [28] have demonstrated the efficacy and safety of pico toning technique with a low fluence picosecond 1,064-nm Nd:YAG laser in Asian female melasma patients. In their study, a 450-picosecond laser was used and it was confirmed that it was effective in treating melasma. We used a 250-picosecond laser in this study. In their study, the modified Melasma Area and Severity Index scoring system was used for analysis, and we used the Mark-Vu skin analysis program. Therefore, it is difficult to simply compare which treatment effect was better. Compared to the 0.6-1.0 fluence used in melasma treatment using the existing 450-picosecond laser, a lower fluence of 0.1-0.5 was used with the 250-picosecond laser. This seems to be helpful because a low fluence can lower the incidence of PIH theoretically.

This study has a few limitations. First, long-term evaluation is required to clarify the potential pigment-lightening effect. Although there are research papers that are effective for various melasma, such as hydroquinone and Vitamin C, we only conducted treatment with the 250-picosecond laser. In fact, it is expected that the combination treatment of those that have been proven effective will produce better effects. In addition, seasonal factors and the use of sunscreen have a great influence on melasma, but we think there are limitations in this area as the study was conducted in a specific month rather than dividing the year at a constant rate. Another limitation of this paper was that the patient group is biased towards women. Realistically, it is unavoidable in that most patients who receive laser treatment for melasma or blemishes are female patients. Because male patients do not visit the hospital for treating melasma or blemishes.

The advantage of this study was that it used that a skin analysis tool Mark-Vu program to add objectivity and confirmed the statistical significance of the results. Another advantage of a picosecond laser is that it can reduce the use of anesthetic cream by causing less pain to the patient as a lower picosecond is used. In fact, in our current study, anesthetic cream was not used on patients except for one patient who was sensitive to pain among a total of 87 patients. Finally, we used only 250-picosecond laser treatment without any other treatment for melasma and pigmented lesions. This can be said to be an advantage in confirming the treatment effect of the picosecond laser without the influence of other treatments.

In the future, the 250-picosecond laser is expected to be used in various skin disease fields by using the characteristics of low picosecond. We confirmed that a low picosecond laser was effective in treating melasma and pigmented lesions. We look forward to trying to graft it into an effective treatment for more diverse diseases in the future.

ACKNOWLEDGMENTS

None.

AUTHOR CONTRIBUTIONS

Conceptualization: SJL. Data curation: DGK. Formal analysis: SJL. Funding acquisition: ESP. Investigation: all authors. Methodology: all authors. Project administration: all authors. Software: DGK. Validation: ESP. Visualization: DGK. Writing–original draft: SJL, DGK. Writing–review & editing: all authors.

CONFLICT OF INTEREST

Eun Soo Park is an editorial board member of the journal but was not involved in the review process of this manuscript. Otherwise, there is no conflict of interest to declare.

FUNDING

This work was supported by the Soonchunhyang University Research Fund (2023-0010).

DATA AVAILABILITY

Contact the corresponding author for data availability.

SUPPLEMENTARY MATERIALS

None.

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