Vascular lasers and light sources have evolved significantly since the theory of selective photothermolysis was published in 1983 (Anderson RR, Parrish JA. Science. 1983;220(4596):524-527). This month’s column will review some interesting recent developments in the field of vascular lasers.
Roy Geronemus, M.D., and colleagues reported their experience with a novel 532 nm potassium titanyl phosphate (KTP) laser (Excel V, Cutera) for port wine stains (PWS) (Reddy KK, Brauer JA, J Drugs Dermatol. 2013;12(1):66-71). Five subjects were enrolled with PWS of the body that had previously been treated with multiple pulsed dye laser (PDL) sessions with what they termed mild or unsatisfactory response.
The investigators treated the PWS at four different purpuric KTP laser settings with the following parameter ranges: 4.8-9 J/cm2, 6-10 mm spot, 3 ms to 6 ms pulse duration, 5 degrees Celsius contact cooling, and left an adjacent control site untreated. After the single treatment all sites exhibited at least 1 grade of color improvement.
Immediate post-treatment histology showed vascular injury up to 4 mm depth and one-month follow-up histology revealed reduction in number of vessels and vessel diameter at all levels of the dermis. The authors state that the combination of large spot sizes and short pulse durations allows for considerable penetration of the KTP laser, and perhaps more effective treatment of many different cutaneous vascular lesions.
Approximately 20 percent of PWS are estimated to be resistant to PDL (Renfro L, Geronemus RG. Arch Dermatol. 1993;129(2):182-188). A group from Germany recently reported a unique approach to PWS laser treatment (Klein A, Szeimies R-M, Bäumler W, et al. Br J Dermatol. 2012;167(2):333-342). In a trial of 28 patients with PWS, researchers utilized intravenous indocyanine green (ICG), an exogenous chromophore with a maximum absorption at approximately 810 nm, followed by an 805 nm diode laser (20-50 J cm/2, 10-25 ms pulse), which affords deeper penetration depth than PDL. Controls included PDL (6 J/cm2, 0.45 ms pulse) and diode without ICG.
Blinded investigators favored the cosmetic appearance and clearance of the diode plus ICG group, though the results did not achieve significance. Despite the greater level of discomfort of the combination treatment, a significantly higher percentage of patients preferred diode plus ICG to PDL. Histology revealed clearance of large vessels >20µm, but not smaller vessels typically present in PWS resistant to PDL.
The authors noted that the parameters have yet to be optimized, however this combination treatment was safe, well tolerated, and could represent a breakthrough in the laser treatment of PWS.
Vascular lasers have multiple applications beyond treating cutaneous vascular lesions, including scars, striae and verrucae, among others. Two recent studies have bolstered the evidence of the 595 nm PDL for the treatment of nail psoriasis. Pulsed dye laser is thought to improve psoriatic lesions by targeting their supporting vasculature, as well as by reducing the number of helper and cytotoxic T cells and normalizing epidermal turnover (Hern S, Stanton AWB, Mellor RH, et al. Br J Dermatol. 2005;152(1):60-65).
A 2012 report out of Thailand described 20 patients with nail psoriasis treated on one hand with PDL (V-beam, Candela) at the following settings: 9 J/cm2, 7 mm spot, 6 ms pulse duration, 20 ms cryogen, 10 ms delay, and the contralateral hand at 6 J/cm2, 7 mm, 0.45 ms (Treewittayapoom C, Singvahanont P, Chanprapaph K, Haneke E. J Am Acad Dermatol. 2012;66(5):807-812). Investigators treated the lateral and proximal nail folds as well as the lunula with two passes and 10 percent overlap for a total of six monthly sessions.
Both the short- and long-pulsed PDL-treated nails achieved a statistically significant improvement from baseline in Nail Psoriasis Severity Index (NAPSI). There was no difference in improvement between the two pulse duration groups, however the long-pulsed treatments were associated with more discomfort.
A group from Taiwan reported the first controlled study of PDL for nail psoriasis with their evaluation of 19 patients (Huang YC, Chou C-L, Chiang Y-Y. Lasers Surg Med. 2013;45(2):102-107). On the control hand, patients applied tazarotene 0.1 percent cream daily to all nails, whereas on the treatment side patients applied tazarotene cream and received six monthly PDL treatments (V-beam) with the following settings: 9 J/cm2, 7 mm spot, 1.5 ms pulse duration, 30 ms cryogen, 30 ms delay.
One pass of pulses with 10 percent overlap was applied to the proximal and lateral nail folds. The investigators found a statistically significant decrease in NAPSI score in the PDL treatment group versus the control.
The Physician’s Global Assessment also revealed a significantly greater amount of PDL-treated patients in the >75 percent improvement group than control. Seventy percent of patients would recommend PDL treatment to other nail psoriasis sufferers. The authors reported more improvement in nail matrix lesions (nail pitting, deformity) than nail bed lesions (oil spots, onycholysis) and hypothesize that this is because they did not treat the lunula.
Of note, “vesicles” formed after the first treatment with one patient, and the fluence was decreased to 8 J/cm2 for subsequent treatments. Nail psoriasis can cause considerable social distress and at times be painful. Based on the findings of these two studies, PDL can provide an attractive therapeutic option for patients looking to avoid systemic medications.
Though vascular lasers have been used for over 30 years, new research, like the studies above, has brought us to a higher level of clinical expertise. Congratulations to all who contribute to the quest.