Negishi et al.36 proposed that latent melasma that was not visible with the unaided eye might have exacerbated after IPL therapy. They called this latent melasma ‘very subtle epidermal melasma’ (VSEM) and found that about 30% of all women without visible melasma had VSEM in ultraviolet (UV) photography.36
In other words, subtle melasma can be often present in patients without visible lesions and can develop into noticeable melasma after aggressive IPL treatment. As IPL therapy was too often followed by development of visible hyperpigmentation,36,37 or worsening of existing melasma lesions,38 the notion that IPL is risky in patients with melasma began to spread widely among dermatologists.
We are of belief that an appropriate use of IPL can be very effective in the treatment of melasma. Melasma may worsen after IPL because improper parameters, which are more suitable for treating solar lentigines or freckles, are used. Excessive heating of tissues can worsen melasma. In fact, dermatologists who frequently utilize IPL in melasma use lower fluences than those used in solar lentigines or freckles.
This is similar to the difference between high-fluence 1,064 nm QS Nd:YAG Laser and low-fluence Laser toning. However, unlike Laser toning, IPL used in melasma does not target destruction of melanin pigments or melanosomes. IPL has a longer pulse width than that of the QS Nd:YAG Laser and delivers thermal energy to the entire epidermis through melanin pigments and melanosomes to increase epidermal turn-over and improve degenerated skin environments.
Therefore, the mechanism of action differs between IPL and Laser toning, which allows them to complement each other. As most patients with melasma also present other pigmented lesions, combining IPL with Laser toning can bring superior and faster improvement than using Laser toning alone. For these reasons, we prefer combining Laser toning with IPL.
In agreement with our experience, recent studies have reported that low-fluence IPL therapy is safe and effective,39 and combining IPL and Laser toning can bring excellent outcomes and rapid improvement.40-42 We expect fractionated IPL will be soon introduced for treatment of melasma,43 and additional research should be performed to support its use.
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4. Fractional Lasers
The concept of fractional photothermolysis (FP) was first introduced by Manstein D et al.44` in their paper published in Lasers in Surgery and Medicine in 2004. Early fractional Lasers were developed to reduce the complications of traditional Laser skin resurfacing. In the early days, the key indication of FP was skin rejuvenation of photodamaged skin and rhytides.
However, some studies reported of successfully treating melasma using a 1,550 nm fractional erbium-doped Laser.45,46 Afterwards, generation and excretion of micro epidermal necrotic debris (MEND), and removal of melanin in this process were clarified,47,48 which served as an underlying principle of fractional Laser therapy in melasma. Favorable reports of ablative and nonablative fractional Lasers in melamsa followed,49-52 and review papers described that fractional Lasers were effective in treatment of melasma.53-55
However, Korean dermatologists who applied fractional Lasers in melasma came to experience much more side effects including PIH and rebound pigmentation than those reported in previous literature. When the energy and density were lowered to reduce side effects, the actual efficacy was much lower than what was reported in clinical studies.
Many dermatologists started to be skeptical of the benefits of FP in melasma. By the late 2000s, skepticism regarding the effects of fractional Laser in melasma had grown and many studies reported of a high risk of side effects and low efficacy.2,56-58
These negative results were particularly pronounced in studies involving Asian patients. The discrepancy in the results between Asians and Caucasians may stem from racial and genetic differences. Lee et al.56 reported that melasma initially improved in the early phase of the treatment but worsened starting with the third treatment.
They raised questions about the long-term results. Nonspecific thermal stimulation is inevitable to remove melanin through MEND and inflammation takes place as a reaction to the excess heat. Therefore, FP may bring temporary improvement of melasma but is likely to worsen melasma through inflammatory response in the long run.
Controversy still exists over the use of fractional Laser in treatment of melasma. We believe that fractional Lasers can play a significant role if they are combined with Laser toning. As mentioned earlier, there is a high probability of low effect and high risk of side effects in the treatment conducted on the basis of the old concept that FP can be effective in melasma by removing melanin pigments through MEND.
However, when combined with Laser toning for the purpose of improving the dermal environment, fractional Lasers may bring excellent long-term benefits.
As for histopathology of melasma, basic characteristics of the condition include increased melanin in all epidermal layers, basal hyperpigmentation, solar elastosis, and epidermal flattening.59-61 Melanocytes in the melasma lesion are larger and have more developed dendrites compared to those in the normal tissues.59-61 The basement membrane is also damaged, presenting pendulous melanocytes that protrude into the dermis.62,63
Along with these findings, other noticeable histochemical characteristics include increased inflammatory cytokines, elevated levels of melanogenesis-associated proteins, and signs suggesting UV-induced skin damage. Dermal inflammation caused by accumulated UV irradiation stimulates fibroblasts which increase dermal stem cell factors and various cytokines.64 These seem to lead to increased melanogenesis.64
UV irradiation also activates matrix metalloproteinases which results in the damaged basement membrane.63 For these reasons, it has been proposed that the treatment goal of FP in melasma should be the improvement of the altered dermal environment to rectify the aberrant signals between dermis and epidermis.
Therefore, Laser toning which is effective in removing melanin, and fractional Laser which is effective in improving the dermal environment can be combined to enhance the therapeutic effect in melasma. As the benefits and risks can differ greatly across patients and lesion types, parameters should be delicately adjusted to maximize the effect and minimize complications.
-To be continued
References
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