Mechanism of Action

Recent data
suggests the role of cutaneous vasculature in the pathogenesis of melasma.
Pulsed dye laser (585 nm)  targets the
melanin and cutaneous vasculature. Vascular endothelial growth factor receptors
1 and 2, expressed by melanocytes, are involved in the pigmentation process. Thus,
by targeting the vascular component, the stimulation of melanocytes can be
prevented. This resultsinto better clinical response and decrease risk of recurrence
of melasma.

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Efficacy

There is paucity of studies of efficacy and
safety profile of PDL in melasma. A study of 17 patients with melasma who were
treated with PDL and TCC.7 The combination treatment was compared
with TCC alone. The laser treatment was started after 1 month of TCC
applications. Three sessions were performed at 3 weekly intervals at the
following settings: fluence 7–10 J/cm2 and pulse duration 1.5 ms.
The authors found that the combination treatment had greater treatment
satisfaction in patients with skin phototypes II and III. PIH was reported in 3
cases.

Fractional
Lasers

Mechanism of Action

In laser therapy, fractional photothermolysis
is a new concept in which multiple microscopic zones of thermal damage are
created leaving the majority of the skin intact, that serves as a reservoir for
healing. The multiple columns of thermal damage are called microthermal
treatment zones (MTZ) and lead to extrusion of microscopic epidermal necrotic
debris (MENDs) that includes pigment in the basal layer. The migration of MENDs
is facilitated by the viable keratinocytes at the wound margins.

Fractional laser therapy does not create an open
wound. The stratum corneum is found to be intact after 24 hours of treatment. This
lead to the faster recovery, lesser risk of scarring so areas such as neck and
chest that are more prone to scarring can be safely treated and complications
of open wounds such as hyper- or hypopigmentation are avoided. Also, greater
depths of penetration can be achieved as entire skin surface is not ablated.
Hence, dermal melasma can be targeted.

Efficacy

Goldberg et al.9
has shown a reduced number of melanocytes after fractional laser which means
that this laser delayed pigmentation.

In a randomized controlled trial by Kroon et
al.,8 20 female patients with moderate to severe melasma were
treated with either nonablative fractional laser (performed every 2 weeks for a
total of four sessions) or TTT (once daily for 8 weeks). A density of
2,000–2,500 MTZ/cm2 with energy per microbeam of 10 mJ. Improvement was same in both the
groups, but treatment satisfaction and recommendation was higher in laser group.
Also, recurrence was noted in both the groups and no case of PIH was seen.

Density used in the melasma treatment varied from
2,000 MTZ/cm2 to 2,500 MTZ/cm2 and energy levels 10–15 mJ/mb.
The treatment sessions varied from 2 to 6 at an interval of 1–4 weeks. Studies have
shown variable results on efficacy.

Intense Pulse Light

Mechanism of Action

The mechanism of effectiveness of IPL involves
absorption of light energy by melanin in keratinocytes and melanocytes leading
to epidermal coagulation due to photothermolysis followed by microcrust
formation.10These crusts containing melanin are shed off hence, the
clinical improvement in pigmentation.

Efficacy

Zoccali et al.
treated 38 patients with melasma using cut off filters of 550 nm, pulse of 5–10
ms, pulse delay of 10–20 ms, and low fluence 6–14 J/cm2 and found
80–100% clearance in 47% of patients.11 The number of sessions used
was 3–5 at interval of 40–45 days. No side effects were reported. 500–550 nm
filters can be used initially and for epidermal lesions, whereas higher
wavelength filters can be used to target deeper melanin in patients with dermal/mixed
melasma. The fluence can be modulated in relation to the anatomic sites.
Although, single pulses heat pigment well, but double or triple pulses should
be used as they reduce the thermal damage by allowing the epidermis to cool
while the target stays warm. The pulse duration used in the studies varied from
3 ms to 5 ms. Average pulse delay used was 10–20 ms. It is important that delay
time between pulses should not be below 10 ms as this inturn increases the risk
of thermal damage as the targeted tissue cannot reduce its temperature within
that time. Average number of sessions used in these studies was 2–5 at an
interval of 4–8 weeks. However, more number of sessions is required for
maintenance and it decreases the chances of recurrence.

 

IPL is found to be effective for epidermal
melasma while, dermal or mixed or refractory melasma can be targeted with
higher fluencies. In darker skin, the risk of PIH should be always be kept in
mind. Use of low fluences and long delay between pulses in such cases can be
helpful. Also, pre and post treatment sun protection and hydroquinone should be
used.

 

Also, combination of ablative and pigment
selective lasers has been tried in melasma. Ablative lasers remove the
epidermis (containing excess melanin and abnormal melanocytes), followed by the
use of Q-switched pigment selective laser that reach deeper lesion in dermis
(dermal melanophages) have been tried without causing serious side effects.

Lasers
in the Future

Recently, FDA has approved Fractional Er:YAG
laser for melasma. The Thulium laser and Copper Bromide laser appear promising
but have been tried in small number of patients, so larger studies are needed
with cautious analysis of results.

Picosecond lasers are now available with laser
output of 532nm, 755nm and 1064nm. However, these have not been tried in
melasma. However, theoretically they may be more effective in removing pigment
due to the shorter laser pulse duration that cause pigment fragmentation. The
damage to surrounding tissue is much less.

Lasers may be used for facilitating delivery of
topical medications known as laser assisted drug delivery (LADD). LADD may be used
to treat patients with dermal type of melasma where topical therapy has not
shown good results. CO2 and Er:YAG ablative lasers can be used to create
transepidermal channels, and thus, facilitating drug delivery to the deeper
layers of the skin.

Similar to LADD, micro needle (MN) technology
can be used deliver cosmeceuticals across the skin by creating micron sized
pores through the epidermis using a roller device with needles.12

In melasma, radiofrequency (RF) devices have
also been used. Cameli et al used a mono polar RF device to facilitate drug
delivery of phytocomplex of 1% kojic acid in 50 patients of melasma.13
MASI score was improved in all patients without any adverse effects. Fractional
RF has also been tried in melasma. Fractional RF causes fractionated
transepidermal elimination of melanin with minimal risk of 

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