Various Applications of Dye Laser and Practical Use of Long-Pulsed Laser

 

We’ve looked into the people, who took the lead in the development of vascular lasers, and learned about dye laser for the treatment of nevus flammeus, which was at the center of the early development phase. With the efforts of Furumoto, who found Candella and Cynosure, Rox Anderson of Harvard Medical School, and O.T. Tan, who led early clinical papers from 1980s to early 1990s, laser treatment has become recognized as a treatment for vascular lesions, but it was not still very effective for thick blood vessels. Since thick blood vessels were mostly treated effectively by sclerotherapy in the US or Europe, it was no wonder that the development of vascular laser for thick blood vessels had been slow.

 

While the development of vascular laser for thick blood vessels was in progress, the use of dye lasers for nevus flammeus was already prevailing and some hospitals have already started using them for vascular diseases other than nevus flammeus. From the late 1990s to early 2000s, dye laser has become the treatment of various vascular skin disease and even lasers for thick blood vessels has started to be used little by little.

What’s interesting here is that most of the lasers for thick blood vessels were similar to the lasers for hair removal. Although I will mention again later in another chapter about lasers for hair removal, what Rox Anderson first introduced for hair removal in the early 1990s was the long-pulsed ruby laser. He then introduced 800nm diode laser for hair removal, which was immediately adapted by Furumoto’s Cynosure and Candella as long-pulsed alexandrite laser for hair removal. Those lasers could be released in less than 1 year because the two companies were already developing long-pulsed alexandrite laser for vascular treatment, not for hair removal. Long-pulsed lasers for vascular treatment and those for hair removal are still made of similar parameters for those reasons. In recent years, you can see long-pulsed lasers that embrace both purposes in the market (e.g. Gentle Max, Elite MPX).

 

 

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1. Various Applications of Dye Laser

When dye laser for vascular lesions (577nm, 300-450us) was first developed, it was for the treatment of lesions made up of thin blood vessels (dozens of um in diameter), especially of nevus flammeus primarily made up of capillaries in infants and children (adults were not considered as appropriate because the blood vessels become dilated with age). As the wavelength became longer and longer to 585nm and 595nm (see the previous chapter) and pulse duration longer and longer (to dozens of ms), however, the indication has expanded as well. The wide use of dye lasers at that time also contributed to various attempts by dermatologists to use dye lasers for the treatment of other vascular lesions.

If you look at the examples of how dye lasers were used in this process, you will learn that the development of lasers was more than just the development of a new treatment. Understanding various applications of dye laser would be also helpful for understanding why the basic knowledge on dermatology is necessary for laser therapies, and why dermatologists who have the basic knowledge on dermatology also need to understand the mechanical properties of lasers for better treatment and expansion of the new applications. It would impossible to name all areas where dye laser was applied in this article, but I will give you several examples that would be helpful for understanding the process of expanding the use of lasers.

 

Verruca

In 1993, O.T. Tan reported in the Lasers in Surgery and Medicine that she could treat 28 out of 39 patients with recalcitrant verrucas on their hands and fingers with 585nm, 340us pulsed-dye laser.

Several more reports followed afterward, although the effects were different among the papers. Combination of PDT and pulsed-dye laser has been reported recently. Verruca is a contagious disease caused by Human Papilloma Virus (HPV), but the histology shows vascular development. Now it seems obvious that damaging blood vessels in a skin disease with vascular development on histology, as in a verruca, could eliminate the cause of the disease as well. But it would have been difficult to come up with the idea of using a vascular laser, such as dye laser, to treat verruca without knowing that verrucas are densely populated with blood vessels of relatively thin diameters.

At any rate, verruca is a good example showing that a disease can be improved or cured by damaging the blood vessels inside, even though they are the consequence, not the cause, of the disease. However, it is also important to remember that laser is not necessarily the best option because there exists various treatments for different location of lesions, which is why most papers are titled with the word ‘recalcitrant’. Laser is a tool that can be considered when previous therapies would not work.

 

Sebaceous Gland Hyperplasia

Sebaceous gland is a hyperplastic skin disease or skin aging, but the histology shows hyperplasia of vessels. Inspired by this finding, German dermatologists reported good results of treatment with pulsed-dye laser in 1997 (Lasers in Surgery and Medicine). I also remember treating sebaceous gland hyperplasia on my forehead after reading this paper.

The treatment uses slightly high fluence with 585nm, 6.5-8J/cm2, and 300-450 microsecond, because the small lesion is less likely to develop a scar.

 

Scar

Scar treatment with dye lase has been reported by many authors from the early 1990s. Dye laser in this case is more for the prevention than for the treatment of an established scar. There are only few cases reported in Korea because patients rarely pay their money to receive a procedure for a barely-there scar. Some reports also suggest that 585nm laser irradiation is helpful immediately after removing surgical suture, but it’s a shame that only few surgeons in Korea have dye laser available.

Considering the fact that angioplasia occurs typically in the early phase of scarring, vascular lasers, especially dye lasers with high vascular selectivity (such as 585nm laser), are expected to be of great help. This is also supported by the fact that papers which reported that dye laser is helpful for scar treatment have used 585nm. Reducing blood vessels is helpful, but injury to the surrounding tissues may lead to growing the scar. 577nm or 585nm can be used, in this regard, for their low fluence and increased selectivity from high HbO2 absorption rate. It is interesting that even the lasers that are not in the market anymore can provide a better effect.

 

Striae

A lot of reports have reported improved striae by low fluence 585nm dye laser since the first report in mid-1990s. Dye laser has been reported as helpful not only for early red striae but also for stimulating collagen production in white striae. People often want the treatment for the striae on their belly even right after delivery if it is helpful. This treatment is not very popular in Korea, however due to the lack of information.

 

Rosacea

Since rosacea is a refractory disease with heterogeneous clinical pattern, various types of lasers and IPL are used for the treatment. The Department of Dermatology, Yonsei University College of Medicine in Korea, recently reported a very interesting paper on rosacea-associated erythema (British Journal of Dermatology, December 2010, Enhancing effect of pretreatment with topical niacin in the treatment of rosacea-associated erythema by 585nm Pulsed Dye Laser in Koreans: A randomized, prospective, split-face trial). According to this paper, 585nm dye laser combined with topical vasodilator cream had superior efficacy than laser monotherapy for rosacea-associated erythema. This study shows that laser can be adaptable to various, creative therapies.

 

2. Development and Practical Use of Various Long-pulsed Lasers

With the use of 532nm KTP or 578nm copper vapor laser for vascular lesions, it was found that long-pulsed laser with relatively long (millisecond) pulse width is more effective and essential for damaging or eliminating thick blood vessels. Since thick blood vessels are located deeper from the skin surface than relatively thinner blood vessels, 532nm or 578nm could not provide a penetration depth that could deliver sufficient energy. In this context, lasers that were easily modifiable to longer pulse duration or existing lasers were introduced for the purpose of damaging thick blood vessels due to deep penetration (longer wavelength translates to deeper penetration depth in a certain wavelength range) and pulse duration suitability, despite incongruity of wavelength. Some lasers were made from existing lasers, others were newly released for vascular use. Because those were not optimal lasers, however, lasers for pigment disorder or hair removal were also included for vessel treatment. Among them were Long-pulsed alexandrite, diode, and Nd:YAG lasers, which have been used for the treatment of thick blood vessels. Endovenous laser treatment, which irradiates laser directly inside the blood vessel, has been also attempted for very thick blood vessels, such as varicose vein. There have been other attempts as well to use laser for the treatment of various diseases consisted of blood vessels. The only success so far has been skin lesions consisted of capillaries that are situated closer to the skin surface and maintaining relatively consistent thickness. Laser therapy is still not so successful for thick and relatively deep vascular lesions because if the system have suitable HbO2 absorption wavelength, pulse duration is no appropriate and if either wavelength and pulse duration is suitable, penetration depth is not enough, or if the system have suitable penetration depth and pulse duration, wavelength is not appropriate.

 

3. Epilogue

Before completing this article about the changes of vascular lasers and clinical use, I would like to quote one of the most experienced dermatologists in nevus flammeus and laser therapy for vascular diseases in Korea, Dr. Kim Yeong-geol (Mapo S&U Dermatology, http://www.allskin.co.kr/) on nevus flammeus treatment:

 

“When patients with nevus flammeus starts treatment, their biggest concerns are whether the lesion could be cured and how long would it take to treat the disease. Doctors who treat nevus flammeus should be able to give a prediction about the prognosis so as to gain certain degree of trust from the patient. Such prediction can be made, however, only by years of continued experience of treating at least hundreds of patients with close observations. Too positive or negative description of prognosis might ruin the possibility of establishing a long-term doctor-patient relationship.

 

“When treating nevus flammeus, the most important and common error is over-treatment. Repetitive over-treatment, without noticing that the previous treatment was not adequate, may lead to an irreversible, tragic outcome. Over-treatment leaves a wound, which definitely ends up as a scar. Eczema emergent during the treatment or erythema exacerbated after the treatment are highly likely to indicate an inadequate treatment. Blood vessels respond to harmful and life-threatening stimulations, such as vascular laser therapy, by revascularization and neovascularization. Moreover, based on my experience, blood vessels seem to generate an environment where they can directly and strongly respond to such damage, and maintain the environment for some time. Such phenomenon becomes most obvious while treating nevus flammeus and seems the biggest obstacle for the treatment. It is widely known that early treatment is most important for nevus flammeus. The problem is that younger patients are more vulnerable to over-treatment, hence more likely to experience the above phenomenon. Therefore, the importance of the initial treatment in children cannot be emphasized enough. Wrongful treatment in the childhood may turn an easily treatable disease to a lifelong incurable disease.”

 

Before and after treatment. Pictures provided by Dr. Kim Yeong-geol, Mapo S&U Dermatology (http://www.allskin.co.kr/)

 

- To be continued -

 

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