Introduction

Chronic sun exposure leads to damage of the epidermis and dermis over time, resulting in rhytides, dyschromia, alterations in skin texture, and skin laxity. In recent years there has been a progressive movement toward nonsurgical interventions for facial rejuvenation. Ablative resurfacing with CO₂ and erbium‐doped yttrium aluminum garnet (Er:YAG) lasers were first used to treat photodamaged skin in the 1980s and remain the gold standard today [1–5]. Yet despite their effectiveness at treating photoaging, there has been a recent push for non‐ablative treatment modalities with less downtime and fewer side effects. There has also been an increased demand for rejuvenation in patients with darker skin types, and non‐ablative lasers have been shown to be safe for this population [6].

Non‐ablative lasers have been used to successfully treat rhytides, dyspigmentation, vascular changes, skin texture, laxity, and scarring [1, 4, 7]. The main goal of these systems is to selectively induce dermal damage, resulting in collagen remodeling and production while sparing the epidermis [1, 2,7–9]. Many different systems have been used with this endpoint in mind (Table 52.1), and they will be discussed in detail below.

Pathophysiology

Non‐ablative rejuvenation systems are composed of lasers, light sources, and radiofrequency devices. Laser systems use energy in the infrared or near infrared spectrum to target specific dermal chromophores, such as water, melanin, and hemoglobin. In contrast, radiofrequency devices produce heat in the dermis and subcutaneous tissue as a result of resistance to current flow through the tissue. Although the mechanisms of action are different, the end result is the same. Both the light sources and radiofrequency devices effectively heat the dermis eliciting a wound healing response without disturbing the integrity of the epidermis [1, 4,10–12].

One of the main effects of photodamage and aging is a reduction in dermal collagen, and this is the target of non‐ablative rejuvenation. It has been proven that thermal induced injury to the dermis causes local release of inflammatory cytokines leading to the proliferation of fibroblasts which results in collagen synthesis [813–16]. In vivo mouse studies have been performed to evaluate collagen composition after treatment with various lasers, and they have all demonstrated a significant change in collagen and extracellular matrix [8, 14].

Non‐ablative modalities

Improvement of the cosmetic appearance of the face depends on the ability to restore damage done over time due to sun exposure. This includes improving red and brown areas, improving skin texture and tone, and reducing the number and depth of rhytides. Many non‐ablative systems have been evaluated for efficacy in facial rejuvenation. Results have been promising and often require multiple treatments in order to appreciate clinical improvement. There are many non‐ablative laser regimens that are effective for facial rejuvenation, and the corresponding studies for each laser will be discussed below. The most common lasers and parameter settings used today are outlined in Table 52.2.

Potassium titanyl phosphate (KTP) 532 nm laser

The 532 nm KTP laser is one of the many modalities used in facial rejuvenation. It is absorbed more intensely by melanin and hemoglobin, and so it is thought that fewer treatments are needed when targeting these components of photodamaged skin [3]. This laser has been shown to effectively target vascular and pigmentary change, skin texture, tightening, acne scars, and rhytides [4, 16].

Lee performed a 150‐person study to compare the efficacy of the KTP laser alone, the long pulsed Nd:YAG alone, or the two modalities combined on collagen enhancement and photorejuvenation [16]. After three to six treatments, all three groups showed statistically significant improvement in rhytides, skin tone and texture, reduction in redness, and improvement in dyschromia. Overall, the KTP laser treated patients showed more improvement than the LP Nd:YAG laser, but the combined treatment group was superior to either group alone. The combined group had a 70–80% improvement in redness and pigmentation, 40–60% improvement in skin texture, tone and tightening, and a 30–40% improvement in rhytides. In addition to these findings, it was also noted that collagen remodeling continues for up to 6–12 months posttreatment, with slow regression in benefit thereafter. Although further studies are necessary, these results suggest that combined modalities may be superior at targeting various factors involved in photodamage and more effectively stimulate collagen production.

A study by Ho and colleagues compared the effectiveness and safety of using the 532 nm LP KTP laser, 595 nm long pulse dye laser (LPDL), 755 nm LP Alexandrite laser, and 532 nm QS Nd:YAG laser for the treatment of freckles or lentigines in Fitzpatrick skin type III and IV Asian patients [17]. Forty patients were enrolled in the study and each patient attended between one and four treatments at 4–6 weeks intervals depending on the clinical response. The laser parameters included a fluence of 12–14 J/cm² and spot size of 2 mm for the LP KTP laser, a fluence of 11–13 J/cm² and spot size of 7 mm for the LPDL, a fluence of 20–35 J/cm² and spot size of 10 mm for the LP Alexandrite laser, and a fluence of 0.6 J/cm² and spot size of 2 mm for the QS Nd:YAG laser. Statistically significant improvement of global and focal facial pigmentation was found after treatment with LP KTP, LPDL, and QS Nd:YAG lasers. No significant improvement was found after treatment with LP Alexandrite laser. Post‐inflammatory hyperpigmentation was absent after LP KTP and LPDL treatment, but was seen in 20% of patients after LP Alexandrite treatment and 10% of patients after QS Nd:YAG treatment. The 532 nm LP KTP and 595 nm LPDL lasers appear to be more effective with less complications compared to the 532 nm QS Nd:YAG and 755 nm LP Alexandrite lasers for the treatment of freckles and lentigines in Fitzpatrick type III and IV skin. The authors also concluded that a long pulse laser and small spot size appear to reduce the risks of lentigines treatment in darker skin types. Another recent study by Negishi et al. evaluated 532 nm KTP laser alone or in combination with LP 1064 to treat dyschromia in 22 Japanese patients. These patients were treated with three sessions 2 weeks apart with one side of the face with 532 and the other with 532 and LP 1064. 532 was shown to be a safe and effective treatment and the addition of 1064 was not clinically apparent but a difference was detected by the 3D skin analysis device [18].

Pulse dye laser (PDL) 585 or 595 nm

The pulse dye laser (PDL) is a yellow light that targets oxyhemoglobin and melanin. It has been used to treat vascular changes and induce new collagen formation. It has been hypothesized that wavelengths targeting hemoglobin disrupt vascular endothelial cells resulting in cytokine release and subsequent collagen remodeling and production [4, 19, 20].

A group of 10 female patients, Fitzpatrick types I–IV, were treated in the periorbital area with the 595 nm flash lamp PDL [20]. One side of the face was treated with the following laser settings: 1.5 ms pulse, fluences of 5–6 J/cm², and a spot size of 7 mm. The contralateral side was treated with a 40 ms pulse duration, fluences of 8–11 J/cm², and a 7 mm spot size. Cryogen cooling was administered for 30 ms with a delay of 30 ms before treatment. Subjects were treated one to two times, and at their 6‐month follow‐up, 70% treated had mild to moderate improvement overall. Sixty percent had equal improvement on both sides despite the different settings. Histologic and electron microscopic evaluation showed a significant increase in papillary dermal collagen, mainly type I.

Another study performed by Bernstein evaluated the effects of treatment of sun damaged skin with a 595 nm long pulse duration PDL [19]. Ten subjects were treated with 10 ms pulse duration, fluences of 8–10 J/cm², and a 10 mm spot size. Improvements were evaluated 8 weeks after treatment with photograph comparison. Blinded physician evaluation of pre‐ and post‐photographs rated improvement in wrinkles in 50%, facial veins improved in 82%, overall redness improved 80%, pigmentary change 61.4%, and a 25% improvement in pore size.

A small clinical trial was performed on 10 patients comparing the efficacy of a long‐pulse PDL (LPDL) versus an intense pulsed light (IPL) on photodamaged facial skin [21]. When compared to the IPL, the LPDL showed greater improvement in lentigines (81% versus 62%), no significant difference in wrinkle reduction between the two groups, and fewer treatments were needed with the LPDL when compared to the IPL (3 versus 6).

In addition to using the PDL laser as a single agent in photorejuvenation, recent trends have shown an effective combination with aminolevulinic acid (ALA) in treatment of photodamaged skin. It is believed that PDL at 595 nm activates protoporphyrin IX, a photosensitizer, which accumulates in photodamaged cells, causing destruction of the cells, release of cytokines, and collagen repair [1]. This is a new and exciting area of research that offers another effective treatment modality for photorejuvenation.