IPL sources and ruby lasers for hair reduction - trying to compare apples and oranges

Abstract

Drs Bjerring et al are to be congratulated for their report on their research entitled ‘Hair reduction using a new intense pulsed light irradiator and a normal mode ruby laser’. This group of studies demonstrates this new intense pulsed light (IPL) source to be nearly four times as effective as the ruby laser. By using the two sides of the face and neck to compare these two light sources one would anticipate meaningful results. Unfortunately, this comparison of broadband irradiation (IPL) and monochromatic ruby laser irradiation is signiŽ cantly  awed, and the results may indeed contribute to an erroneous conclusion. This  aw relates to the choice of a ruby laser that delivers a small spot size (5 mm) being compared to an IPL source with a spot size of 48 3 10 mm. This means that the IPL foot print is 24 times larger than that of the ruby laser. Larger spot size translates to deeper penetration of light which is of distinct importance when we are targeting hair follicles. If we would like to attribute greater effectiveness to the IPL, with its longer wavelengths, then we should have a more even playing Ž eld relative to spot size. Additionally, the authors point out that the ruby laser in their study had a sub-optimal pulse width of less than 1 millisecond. We have learned that in the pursuit of permanent hair reduction, longer pulse widths are beneŽ cial. Hence, the design of this new IPL source included pulse widths from 5–40 milliseconds. Furthermore, this new IPL source enlists the beneŽ t of photon recycling which is absent in the older ruby laser used in this study. Therefore, even though the  uences utilized were nearly identical, photon recycling would enhance efŽ ciency at any wavelength. To summarize, although good control exists by virtue of comparing two similar anatomical sites on the experimental subjects, the absence of controls for spot size, pulse width, and photon recycling disallows any conclusion that broadband irradiation is more effective than monochromatic ruby laser irradiation for permanent hair reduction. Such an erroneous conclusion  ies in the face of our understanding that there is better melanin absorption of 694 nm light than of the longer wavelengths that are part of the emission spectrum of this IPL source. As it happens, there is a ruby laser of more recent design than the one used in this study. Palomar’s E-2000 ruby laser delivers a spot size with four times the area of the Epitouch, with a more appropriate pulse width of 3 milliseconds with an option to pause for 100 milliseconds mid-pulse, and with photon recycling. The one drawback of the ruby laser for hair removal relates to epidermal heating due to the epidermal melanin absorption of 694 nm light. The E-2000’s design therefore, includes a saphire contact cooling tip to minimize the chance of epidermal damage. I would suggest that by comparing the Elipse Relax light 1000, a newly designed IPL source, with a more recently designed normal mode ruby laser like the E-2000, the authors would have results that would be more valid, and they might well come up with different conclusions. Cyrus Chess, MD Dermatologic Laser Center of Connecticut Yale University School of Medicine Medical Director: Cool Laser Optics, Inc. Norwalk, CT 06851-5709 USA