Acne vulgaris is a very common cutaneous disorder which can cause permanent scarring and disfigurement.
Acne is a multifactorial disorder of pilosebaceous units and affects the areas of skin with the greatest concentration of sebaceous follicles such as the face, neck, chest, and back.
Common therapies for acne treatment include retinoids, keratolytic agents, antimicrobials, and anti-inflammatory agents.
The need for an alternative treatment has led to the investigation of lasers and light sources as a new treatment.
The laser and light based devices most commonly used are either the short wavelengths (400–700 nm) i.e., pulsed dye laser, red light or blue light; or longer wavelength lasers (near- and mid-infrared).
The short wavelength lasers cause activation of protoporphyrin-IX resulting in a photodynamic reaction.
The longer wavelength lasers target sebaceous glands resulting in reduction of sebum secretion and improvement of acne. They also induce collagen production resulting in improvement of acne scars.
Introduction
Acne vulgaris is the most common cutaneous disorder that affects approximately 80% of the population at some point during their lives.1 Its prevalence has been estimated to be about 85–100% in boys aged 16–17 years, and 83–85% in girls of the same age.2’3 In fact in the U.S., it is estimated that approximately 25 million adults and 40 million adolescents are affected by this condition.4’5 However, even though it is common in teenagers and early adults, acne can occur in all age groups.6’7
This common cutaneous disorder can cause permanent scarring and disfigurement, which may lead to severe consequences in psychological and personality development. In fact, it is associated with a high prevalence of depression and is the second highest cause of skin disease related suicide. For these reasons effective management of acne can improve self esteem, body image and other life quality issues.8’9
Acne is a multifactorial disorder of pilosebaceous units and affects the areas of skin with the greatest concentration of sebaceous follicles. These areas include the face, neck, chest, and back. The main etiologic factors of acne are complex and multifactorial. There are four key components that contribute to the development of acne, these include (1) hypercornification of follicular epithelium at the infra-infundibulum with the development of a keratin plug blocking outflow of sebum to the skin surface; (2) hyperplasia of the sebaceous glands and hypersecretion of sebum with puberty or increased activity due to androgen hormone stimulation; (3) lipase-synthesizing bacteria (Propionibacterium acnes) colonizing the upper and midportion of the hair follicle, converting lipids within sebum to pro-inflammatory fatty acids; finally, (4) immune response and induction of inflammation in the follicle associated with release of cytotoxic and chemotactic factors.10–13
The severity of acne has been classified by the American Academy of Dermatology according to the following specifications: Mild acne is characterized by the presence of comedones, few papules and pustules (generally <10) but no nodules; Moderate acne has several to many papules and pustules (10–40) along with comedones (10–40); Moderately severe acne is characterized as the presence of <40 papules and pustules along with larger, deeper nodular inflamed lesions (up to 5); Severe acne is characterized by the presence of numerous or extensive papules and pustules, as well as many nodular lesions.14 Although most patients will improve with time, some do not and have serious long term effects from acne. These include redness, hyperpigmentation, and permanent scars (atrophic, hypertrophic and keloids).1
Common therapies used for the treatment of acne vulgaris include keratolytic agents, antimicrobials, anti-inflammatories, retinoids, hormonal treatments, microdermabrasion, and chemical peels.1’9 The need for an alternative treatment has led to the investigation of lasers and light sources as a new treatment. The mechanism of action relies upon the fact that lasers can emit wavelengths in the visible light spectrum (400–700 nm) which can cause self destruction of P. acnes because these bacteria have porphyrins with Q-band absorption peaks in the range of 500–700 nm.15 In addition, long wavelength, near- and mid-infrared lasers, cause photothermal damage to the sebaceous glands because they can penetrate deeper into the skin (Fig. 1a, b).16
Fig. 1
Laser for acne (a) before treatment (b) result after four treatments with 1,064 nm Nd: YAG laser
Laser Based Therapies
The mechanisms of action are that lasers can emit wavelengths which are selectively absorbed by oxyhemoglobin of the dilated vasculature within inflamed acne, activate bacterial porphyrins resulting in self destruction of P. acnes, or decrease sebum production by photothermal damage to the sebaceous glands. |
Pulsed Dye Lasers
The 585-nm and 595-nm pulsed-dye lasers (PDL) directly targets P. acnes. The PDL uses a yellow light which is mostly absorbed by oxyhemoglobin. For this reason it is especially useful for the treatment of vascular lesions as well as scars and fine wrinkles. However, the pulsed dye laser can also activate bacterial porphyrins and thereby produce selective photothermolysis of the dilated vasculature within inflamed acne.17–19
Orringer and co-workers conducted a randomized controlled split-face study with the 585-nm PDL, however their study did not find any significant improvement in treated versus non-treated skin.20 In contrast, Seaton and co-workers found that this wavelength reduced inflammatory acne lesions by 49% at 12 weeks after one treatment.21 No serious adverse affect to the treatment was noted in this study.
Potassium Titanyl Phosphate (KTP) Laser
The 532 nm potassium-titanyl-phosphate (KTP) laser uses a broad spectrum green light which is thought to photoactivate bacterial porphyrins and produce limited non-specific thermal injury to sebaceous glands.22–24 Baugh and Kucaba conducted a study to evaluate the 532-nm KTP laser for the treatment of mild to moderate acne. This study was a randomized split-face study of 26 patients that showed a moderate reduction in acne score at 1 week and diminished reduction at 4 weeks post-treatment.25
Bowes and co-workers conducted another split-face study whereby they treated one-half of the face of 11 patients with mild to moderate acne with the KTP laser. After 1 month, the treated half had a 35.9% decrease in acne, while the control half had a 1.8% increase. They noted in this study that there was decreased sebum production but there was a minimal effect on P. acnes.23
1,450-nm Diode Laser
The 1,450 nm diode laser is a longer wavelength laser that penetrates to the level of the sebaceous gland within the mid-dermis.26 This wavelength is primarily absorbed by water, so it does not greatly effect the epidermis but does thermally ablate sebocytes, along with P. acnes.26’27 In a multicenter, blinded study, 61 patients were treated every month for 4 consecutive months using the 1,450 nm diode. There was a 26% drop out rate, but of the 45 patients remaining, 26 had 65% improvement 1 month following treatment, and at 6 months 5 patients required no additional acne therapy.28
Friedman and co-workers observed an 83% decrease in mean inflammatory facial acne lesions after three treatments using a 1,450 nm diode at 4–6-week intervals. Side effects were transient and local, including erythema, edema, and perioral pain. However, this study was limited in that there was no control and no long-term follow up.27
Alam and co-workers compared the 1,450 nm diode laser with the 595 nm PDL and determined that the 1,450 nm diode laser produced similar acne reduction with longer remissions (up to 3 months) when compared to the 595 nm PDL in a split-face trial of 25 patients after 4 monthly treatments.29
1,320 Neodymium: Yttrium Aluminum Garnet Laser (ND:YAG)
The 1,320 neodymium: yttrium aluminum garnet laser (Nd:YAG) is a deep-penetrating, long wavelength, mid-infrared laser that has been shown to have thermolytic effects upon sebaceous glands. In one study the 1,320 Nd: YAG laser was used to treat 50 moderate to severe acne patients with 6-weekly treatments. The patients were followed for 1 year thereafter. Eighty percent of patients felt they had 75–100% improvement after the fourth of these six treatments. However, 72% of the patients felt that the benefit seemed to fade beyond 3 months. Eighty two percent of the patients that had acne scarring had ‘noticeable’ improvement. The one major complication that was reported was one patient developed a pitted scar from the treatment.30
1,540 Erbium (ER): Glass Laser
The 1,540 erbium (Er): glass laser was initially used for non-ablative dermal remodeling and wrinkle reduction. However, this laser was shown to provide deep dermal penetration and subsequent alteration of sebaceous activity through thermal coagulation. Two studies that have looked at the effects of the 1,540 erbium (Er): glass laser have found very promising results. One study found that there was a 78% lesion reduction in 25 patients with facial and truncal acne after 4 monthly treatments with the 1,540 nm laser.31 The other study found that there was a 70% reduction in 20 patients with facial acne who received four bi-weekly treatments.32 Both studies had no reported adverse effects and had a reduction of oiliness in their patients.31’32
Light Based Therapies
The three light based devices most commonly used are the blue light, red light, and intense pulsed light system. They can cause self destruction of P. acnes by activation of protoporphyrin IX to produce free radicals. |
Blue Light
Light based therapies takes advantage of the photosensitivity of porphyrins produced by P. acnes. Activation of protoporphyrin IX, found in P. acnes, in the presence of oxygen produces a metastable intermediate that destroys the bacterium. Protoporphyrin IX absorption peaks occurs in wavelengths found in the visible light spectrum.33–36
In a study done by Elman and co-workers, 46 acne patients were treated with blue light. Of these 46 patients, 80% of them received approximately a 60% improvement of papulo-nodular acne lesions after 8 treatments. These patients had prolonged remission of their acne which was evident in the 8 weeks follow-up period. No adverse effects were noted in any of the patients.37 In a split face study conducted by Tzung and co-workers, they found that the treated half when compared with the non-irradiated side, was markedly improved and concluded that blue light was effective in acne treatment.38
In a study by Tremblay and co-workers, 45 patients were treated with pure blue light (415 nm and 48 J/cm2) for a period of 4–8 weeks. They found that the mean improvement score was 3.14 at 4 weeks and 2.90 at 8 weeks. In fact, nine patients experienced complete clearing at 8 weeks. The treatment was well tolerated, with 50% of patients highly satisfied with the treatment. There were no reported adverse effects in this study.39
In a study by Omi and colleagues, they investigated the use of high-intensity, narrow-band, blue light on acne. They recruited a total of 28 adult healthy volunteers with facial acne (mean age 28.1 years, range 16–56 years). These patients were treated with a total of eight serial biweekly 15-min treatment sessions. They found that overall there was a 64.7% improvement in acne lesions.40
Morton and co-workers tried to determine the effect of narrow-band blue light in the reduction of inflammatory and non-inflammatory lesions in patients with mild to moderate acne. They performed an open study utilizing a blue light source in 30 patients with mild to moderate facial acne. Over a 4 week period, patients received eight 10- or 20-min light treatments, peak wavelength 409–419 nm at 40 mW/cm2
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