Lasers for the treatment of hyperpigmentation

Ideally, the goal of laser therapy is to reduce the occurrence of chromatin changes, as well as to reduce the risk of scarring and permanent dyschromia.

Laser systems for the treatment of hyperpigmentation can be divided into:

• surgical lasers;
• Q-switched neodymium yttrium garnet lasers (532 nm), Q-switched ruby ​​lasers (694 nm), Alexandrite lasers (755 nm), Q-switched neodymium yttrium garnet lasers (1064 nm) ;
• laser systems based on the action of high-intensity light pulses (500 - 1200 nm).

Surgical lasers

Surgical lasers (typically used to treat lesions such as seborrheic keratosis, warts, syringomas, trichoepitheliomas, verrucous mole, xanthoma squamous, rhinophyma) may also help treat hyperpigmentation by reducing tissue ablation with partially selective thermal damage and little risk of scarring and dyschromia. The Q-switched neodymium yttrium aluminum garnet laser emits light at a wavelength of 2940 nm, which is well absorbed by water and penetrates much less than CO₂ lasers, thus ablating the skin with minimal thermal damage.

Fractional photothermolysis is a relatively new concept in laser therapy, in which numerous microscopic areas of thermal damage are created, while leaving most of the skin intact. Fractional laser radiation is delivered using points (acupressure therapy) that generate microzones of ablative and thermal damage (microthermal zones; MTZ) that alternate with healthy tissue. In the treated microzones, the controlled release of heat leads to instant tissue shrinkage and stimulates neocollagenesis. Zones of healthy tissue between the treated areas provide rapid healing and a significant reduction in the recovery period, as well as redness after the procedure. The exclusive radiation system makes it possible to control tissue damage while maximizing efficiency.

Q-switched lasers

Melanosome varies between 50 ns and 500 ns with a wide spectrum of melanin absorption. Q-switched lasers (neodymium yttrium aluminum garnet lasers, ruby ​​and alexandrite lasers) send nanosecond pulses; therefore they are selectively targeted to melanosomes with minimal heat diffusion.

Q-switched ruby ​​lasers

Q-switched ruby ​​lasers at 694 nm are more selective for melanin than Q-switched neodymium yttrium garnet lasers (1064 nm). In theory, they should be more efficient than Q-switched neodymium yttrium aluminum garnet lasers, but the role of the ruby ​​laser is controversial. Studies have shown different results. In particular, they have the disadvantage that a deeply pigmented epidermis can create resistance to the penetration of light into the dermis, and unwanted damage to the epidermis can lead to dyspigmentation. In general, Q-switched ruby ​​lasers are not recommended for the treatment of hyperpigmentation problems in dark-skinned patients (Fitzpatrick skin types IV - VI).

Q-switched neodymium yttrium aluminum garnet lasers

Waves of 532 nm Q-switched neodymium yttrium aluminum garnet lasers are well absorbed by melanin, while longer wavelengths cause minimal damage to the epidermis and are not absorbed by hemoglobin. Deeper skin penetration also allows doctors to target melanin in the dermis. Small doses of such radiation cause sublethal lesions of melanosomes, leading to fragmentation and disintegration of melanin granules into the cytoplasm. This action is very effective for melanosomes, since the waves are well absorbed by melanin in other structures. Longer wavelength Q-switched neodymium garnet lasers are the safest type of laser therapy for dark skinned patients.

Q-switched alexandrite laser

The long wavelength of the 755nm Q-switched Alexandrite laser provides deeper penetration into the skin. Unlike other Q-switched lasers, the alexandrite laser can be used with short pulses (5 ms). This type of laser makes selective pigmentation damage possible. However, it poses a greater risk of dyschromia. Research suggests using a combination of low-energy Q-switched alexandrite lasers and Q-switched neodymium yttrium aluminum garnet lasers to effectively treat hyperpigmentation, especially the "light brown" type.

High Intensity Light (HIL) pulses in the treatment of hyperpigmentation

The IVS is a non-laser light source that emits light in the range of 515 nm (red/yellow) to 1200 nm (infrared). The advantage of the IVS is the variety of parameters. Wavelength, radiation density, number, duration and delay of pulses can be individually adjusted for each patient for effective targeting of chromophores. Also, IVS can be widely used to treat many diseases, including vascular damage, melanocyte damage and hair removal. The authors' experience shows that the use of IVS makes it possible to ablate superficial pigmented lesions with partially selective thermal lesions and a low level of scarring, but with a high risk of discoloration.

Laser units play an important role in treatment. Initially, 500-550 nm filters can be used for epidermal lesions, and longer wavelength filters can be used to target deeper melanin, such as in patients with dermal/mixed melasma. Density can be adjusted to the areas to be treated, so a higher density can be used for the cheeks and cheekbones, while a lower density can be used for the eye and neck areas. Higher density is used for deeper lesions, but may lead to post-inflammatory hyperpigmentation of the skin in dark-skinned patients. Single pulses are effective at heating the pigment, while double or triple pulses are used to reduce thermal damage by allowing the epidermis to cool while the target remains warm.

According to Prime magazine.