SLR - April 2014 - Archibald J. Loch
Reference: Caney C, Cantrell W. Treatment of Onychomycosis Using a Submillisecond1064-nm Neodymium:Yttrium-Aluminum-Garnet Laser. J Am Acad Dermatol 2013; 69(4): 578-582
Scientific Literature Review
Reviewed By: Archibald J. Loch, DPM
Residency Program: Massachusetts General Hospital, Boston, MA
Podiatric Relevance: Over the last decade there has been a large influx in the number and type of lasers and light therapies available for the treatment of onychomycosis. These new therapies have offered clinicians a source of therapy with minimal side effects and few contraindications. This study investigates the mechanism of action, clinical efficacy and safety of the first FDA approved device for cosmetic improvement of onychomycosis.
Methods: A four-part in vitro and in vivo study was conducted using a Nd:YAG 1064-nm laser. The firs part of the study evaluated three different nail pathogens: T. Rubrum, E. Floccosum and S Dimidiatum, in suspension. The pathogens were exposed to one of seven time intervals from 2-15 minutes and heat exposures ranging from 45ºC - 55ºC. The suspensions were then plated and observed for growth post heat exposure. The second and third parts of the study consisted of irradiating pure fungal colonies and measuring their resultant growth post treatment. The fourth and final portion involved in vivo treatment of toenails diagnosed with onychomycosis both clinically and culture-proven, over five treatment sessions in 24 weeks with the Nd:YAG laser.
Results: A fungicidal effect for Trichophyton Rubrum was seen at 50ºC after 15 minutes, and for Epidermophyton Floccosum at 50ºC after 10 minutes. Limited growth of Scytalidium was seen at 55ºC after five minutes. No inhibition of growth was observed after laser treatment of fungal colonies in suspensions. In vivo treatment of toenails overall showed no improvement in Onychomycosis Severity Index score and did not result in onychomycosis cure, although marked improvement was seen in some individuals.
Conclusions: Laser treatment of onychomycosis was not related to thermal damage or direct laser effects on fungal viability. It has been reported that temperatures of 55ºC are necessary to kill dermatophytes via heat, and in vivo studies with this laser have never shown temperatures to exceed 50ºC. A well designed clinical trial is needed to better examine the parameters used in laser treatment for onychomycosis.