Facial Pigmentation - How can I get rid of it?
Dr Rachel Teoh, MBBS, Dip Fam Med, Dip Derm
Skin pigmentation or brown spots on the skin are very common especially in Asians. It is usually due to an increased deposition of melanin. Rarely, it can be caused by the deposition in the dermis of endogenous or exogenous pigments such as hemosiderin, iron or heavy metals. Facial pigmentation is one of the most common reasons for dermatologic consultation especially for darker skin types. Although skin pigmentation is not harmful, it can cause significant cosmetic disfigurement and become a persistent psychosocial burden.
The diagnosis of most skin pigmentation is made on clinical grounds. In most cases, the initial evaluation involves a detailed family and personal medical history and a complete physical examination. It is most important to visit a trusted doctor to obtain an accurate diagnosis before embarking on any treatment.
Pigment lasers are very effective for treating sun spots and freckles which usually affect the top layer of the skin. The use of laser for cutaneous hyperpigmentation is based on the clinical application of the theory of selective photothermolysis. The wavelength of light delivered should be preferentially absorbed by the target molecule (chromophore). To limit the damage to adjacent cutaneous structures, the light must be delivered within a period of time and the light energy transferred to the target chromophore must be sufficient to exert the desired therapeutic effect.
Principles of light therapy
Absorption of light by melanin progressively decreases with increasing wavelengths of light. In contrast, the absorption of light by water molecules generally increases as wavelengths increase. Oxyhemoglobin has two peaks of light absorption within the visible light range. Although one might interpret this to mean that lasers that emit ultraviolet light or short wavelengths of visible light would be preferred for the treatment of skin pigmentation, additional factors such as competition with hemoglobin (a chromophore with peak light absorption between 400 and 600 nm) and the limited depth of penetration of very short wavelengths of light, limit the spectrum of optimal clinical use.
Q-switched nanosecond lasers deliver exceptionally high energy laser pulses with pulse durations in the nanosecond range. Absorption of light by melanin create acoustic shock waves within melanosomes, which breaks up the melanocytes and melanosomes.
Picosecond lasers deliver an optical pulse duration that is less than 1 nanosecond. A picosecond is one trillionth of a second. The extremely short pulse duration create more of a photoacoustic effect than a photothermal effect on target tissue, as compared to Q-switched nanosecond lasers. This helps to treat even smaller particles than nanosecond lasers, use less energy and reduce thermal damage to adjacent cutaneous structures.
Ablative lasers treat superficial skin pigmentation in a nonselective manner through the vaporization of the epidermis and superficial dermis. The 10,600 nm carbon dioxide (CO2) and 2940 nm erbium:yttrium aluminum garnet (Er:YAG) lasers can be used to ablate pigment-containing skin. However, ablative laser is a less popular option in treating pigmentation.
Fractionated lasers, both nonablative and ablative, create multiple microscopic vertical columns of thermally damaged skin in the epidermis and dermis (microthermal zones). After treatment, the wound healing process leads to remodelling and normalization of the treated tissue.
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Disclaimer: This article is not intended to be a substitute for medical advice and readers are advised to seek advice from me personally.