Can Compact Lasers Have An Impact For Onychomycosis?

In recent years, laser therapy has emerged as a possible treatment option for onychomycosis. Given the variety of available lasers, this author offers insights on a couple of compact laser systems and provides a helpful primer on the technology behind laser therapy modalities.

Onychomycosis has been a historic problem because fungi are hardy and robust organisms with spores and hyphae that can survive under conditions and at temperatures more extreme than most human cells can tolerate. Many species are anaerobic or require little oxygen, and most flourish under the conditions of warm temperature and high moisture. Regions beneath the nail plate and within the nail bed and matrix form a nearly ideal environment, providing fungal colonies the ideal environment for growth.

   Topical antifungal agents have a hard time getting through and maintaining a presence long enough to be effective. Systemic antifungal medications, such as terbinafine (Lamisil, Novartis), can attack the colony from below but terbinafine can have unpleasant and sometimes serious side effects. These include liver damage, severe skin reactions and, in some cases, reported death.1 Manufacturers of oral antifungals recommend repeated blood tests, which is the standard of care.

   Most thermal therapies, including some laser therapies, are limited because dermal cells and pain sensors under the nail plate are more sensitive to temperature rises than the fungi. In addition, the use of laser therapy is contraindicated in patients with compromised circulation and a lack of sensation as it may cause burning and tissue injury.

   Light in the near infrared spectrum and specifically at wavelengths around 1 µm transmits well through the nail plate, even when it is reasonably compromised by infection. Most dermal tissues absorb such wavelengths as 1,064 nm but the penetration is less than 1 cm. The fungi that colonize the nail more strongly absorb these wavelengths. (For more insights on how lasers function, see the sidebar “What You Should Know About The Science Behind Lasers” at the right.)

A Closer Look At The Potential Benefits Of Compact Laser Systems

Unfortunately, in my experience, there is currently no insurance coverage for the use of laser therapy to treat onychomycosis. We are currently in a market where it is crucial to offer a reasonably priced treatment to the public. When purchasing a laser, it is essential to acquire one that is cost-effective, offers multiple treatment functions for podiatry and is affordable at the same time.

   Granted, there are many choices when it comes to offering laser therapy to our patients. The use of diode lasers provides the perfect opportunity for podiatrists to treat pain and inflammation without the use of local steroid injections and/or non-steroidal anti-inflammatory drugs (NSAIDs). Over the years, hundreds of patients have received referrals to or sought out my practice due to this physical medicine aspect of diode lasers.

   Today, there are therapeutic lasers available with average power levels, typically in the range of 5 W to 30 W per diode, which deliver the necessary dose at the needed depth of penetration in a reasonable amount of time. The cost per average watt per treatment minute at the needed depth of penetration is well within the financial model of the average patient.

   Nexus lasers (USA Laser) provide the necessary power density and dose at all levels of tissue depth to produce excellent clinical results that increase patient referrals. The Nexus laser weighs less than 3 pounds and is essentially a combination of a diode laser and a surgical laser. It has two hand-pieces, one for pain and inflammation and one for soft tissue ablation, which includes warts and toenail fungus. It is a replacement for our old CO2 lasers.

   The Nexus family of lasers comes in powers of 7 W, 10 W, 15 W, 20 W, 30 W and 60 W with wavelengths within the therapeutic window. Furthermore, Nexus lasers are all designed with a single diode to ensure the highest power density.

   Another laser of note is the compact Q-Clear laser (Light Age Technology), a Q-switched laser that works on cavitation rather than direct heating of the dermis. Accordingly, the laser does not cause the heat and pain that were characteristic of previous lasers. It is fast and affordable for the patient.

   The Q-Clear laser system is safer and more effective in treating dystrophic nails, particularly those due to onychomycosis, in comparison to previously available methods. In clinical studies, it has demonstrated a 97 percent success rate in providing significant clearance of affected toenails without any significant side effects and without causing pain.6 In addition, the average clearance of the toenail was 57 percent across the board. In these studies, most toenails achieved substantial or complete improvement after only a single treatment. These results occurred using a simple treatment protocol, which generally consisted of laser treatment without the application of adjunctive topical therapies or use of any anesthetic agents, and took less than five minutes per foot. Due to the efficacy, speed and lack of disposables, there are significantly reduced treatment costs that have helping to expand the availability of the treatment.

   The Q-Clear is a Nd:YAG laser system with certain unique properties that differentiate it from lasers that have been used previously in podiatry. Nd:YAG lasers themselves are relatively new in podiatry and the FDA has cleared the laser only within the last year for “the temporary increase of clear nail in patients with onychomycosis,” making Q-Clear only the third such laser system to be FDA cleared for this application.

   The Q-Clear laser system delivers sufficiently high pulse energies in spatial and temporal pulse formats. These formats were designed to provide the heating and photomechanical disruption needed to penetrate and kill the fungal colonies without causing pain or adversely affecting the surrounding tissue. In addition, the cost of treatment (for everything related to the laser system) is under $10 per fully treated foot.

Pertinent Insights On Q-Switching And Nd:YAG Technology

Nd:YAG laser systems provide fundamental light output in the near infrared region of the spectrum. Most commonly, the output is at a wavelength of 1,064 nm, slightly outside of the range of visible light (nominally 400 to 800 nm, violet to deep red). The output of these laser systems can occur in either a continuous wave or in a pulsed format. It is sometimes “frequency doubled” by the nonlinear process called second harmonic generation to the green laser wavelength of 532 nm.

   Of the pulsed format lasers, there are several types that are distinguished by the duration of the laser pulses. The most common are long-pulsed lasers and Q-switched lasers. Long-pulsed lasers have typical pulse durations in the millisecond (10-3 s) to microsecond (10-6 s) range and Q-switched lasers have pulse durations in the nanosecond (10-9) range. For a given pulse energy, generally expressed in units of millijoules or joules, the shorter the pulse duration, the higher the laser’s peak power. Continuous wave and long-pulse lasers interact with biological materials (“biomatter”) dominantly through photothermal means. In other words, the energy in the light absorbed rapidly converts into heat, causing a temperature rise in the material illuminated. Q-switched laser pulses additionally can interact more disruptively, causing photoacoustic, photoablative and other photomechanical effects.

   With lasers, selectivity is key as the anti-targeting of its surroundings can be every bit as important targeting a specific bio-entity. Selective photothermolysis is a process that uses differential light absorption to selectively heat and kill a targeted cell type. One can use this process when there is a wavelength at which the bio-target has stronger specific absorption than the surrounding tissue and when the absorbed energy can be confined within the target for times long enough for thermal necrosis to occur in the target. This process is abetted by poor thermal transport between the target and its surrounding tissue and by good cooling of the anti-targeted tissue due to blood circulation or, when possible, by external means.

In Conclusion

There are several lasers on the market that unfortunately are not well designed for the podiatric market. They are too large, too expensive and cost patients more money than they are willing to spend. The future of podiatry is compact, multi-task lasers that the doctor is able to offer to patients at a reasonable price without extensive marketing. These lasers can also make very nice revenue for the practice.

   Dr. Zuckerman is a Fellow of the American College of Foot and Ankle Surgeons. He practices at Foot Specialists in Woodbury, N.J. and is the Medical Director and CEO of Clearly Beautiful Nails Mobile Laser in Cherry Hill, N.J.

   The author acknowledges Nelson Marquina, MSc, PhD, DC, and Donald Heller, PhD, for their assistance in laser research.

   Editor’s note: Dr. Zuckerman is a consultant to Light Age, Inc.

References

1. Prescribing information, terbinafine (Lamisil, Novartis).

2. Joensen J, Demmink JH, Johnson MI, et al. The thermal effects of therapeutic lasers with 810 and 904 nm wavelengths on human skin. Photomed Laser Surg. 2011; 29(3):145-53.

3. Venezian GC, da Silva MA, Mazzetto RG, Mazzetto MO. Low level laser effects on pain to palpation and electromyographic activity in TMD patients: a double-blind, randomized, placebo-controlled study. Cranio. 2010; 28(2):84-91.

4. Bjordal JM, Couppé C, Chow RT, Tunér J, Ljunggren EA. A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. Aust J Physiother. 2003; 49(2):107-16.

5. Tunér J, Hode L. Laser therapy, clinical practice and scientific background. Prima Books, Sweden, 2002.

6. Data on file, Light Age.