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Scott Nelson

Leading Light Therapy Researcher Explains LED Flicker, Heat Lamp Limitations, and Photobiomodulation Treatment Times

We're fortunate to have one of the world’s leading photomedicine experts, Dr. Michael Hamblin, on our scientific advisory board. Dr. Hamblin has published over 300 peer-reviewed articles on light therapy.

We recently had a conversation where we posed FAQs that we hear again and again from Joovv users and people unsure about light therapy. These are Dr. Hamblin’s answers:

Infrared Heat Lamps Versus Joovv

Joovv: In terms of receiving a clinically-relevant dose within the same treatment time, how does a high-quality LED device like the Joovv compare to 250-Watt infrared heat lamps?

Dr. Hamblin: You would need to spend much, much longer in front of a heat lamp to receive a clinically relevant dose of near-infrared light. The difference between an infrared heat lamp and the Joovv is that the heat lamp puts out mid-infrared and far-infrared wavelengths in addition to near-infrared. These IR wavelengths are absorbed by the body and generate heat. As a result, a person cannot get too near a heat lamp or it will feel uncomfortably warm.

Joovv: We recently used a third-party diagnostic company (Independent Testing Laboratories) to test a series of 250-watt heat lamps. The total light output measured 27 Watts within the 600- 900 nm range and the average irradiance over the surface of the device was 2 mW/cm2 @ 18 inches away. By comparison, at 6” away from the Joovv Solo, the average irradiance over the surface area of the device was 30.4 mW/cm2. Far more than the heat lamp.

Dr. Hamblin: A distance of 18 inches from heat lamps is recommended, and with the highly divergent nature of the heat lamp beam, the power density at that distance will be very low, in the region of the 2 mW/cm2 that you measured.

Ideal Light Therapy Dosage

Joovv: Is there a minimum or maximum amount of Joules that an LED-based light therapy device should be delivering to the body in a given treatment session to induce a biologically-relevant result?

Dr. Hamblin: A few hundred total Joules spread over a reasonable area is probably the least energy that will give a beneficial effect. If a laser is used with a small focused spot, then the total energy will be much smaller. The maximum amount of energy delivered by a full-body device would be in the neighborhood of 200,000 Joules. For many applications, a few thousand Joules is optimal.

LED Flicker

Joovv: Because of the flicker (ripple) effect caused from the residual periodic variation of DC voltage from a power supply, some consumers are concerned that LEDs may be potentially dangerous. What are your thoughts on LED flicker as it pertains to light therapy? Do you think there is any safety risk for the user?

Dr. Hamblin: I do not believe that the “ripple or flicker effect” has any substantial effect on the outcome of photobiomodulation (PBM) treatments. If anything, I suppose it might make the light a tiny bit more effective because it is pulsed, but this is very unlikely. It is certainly not dangerous.

Lasers Versus LEDs

Joovv: In layman’s terms, what are some of the key differences between LED-based light therapy devices and laser-based devices? Do you have a preference?

Dr. Hamblin: If everything else is equal, laser devices can deliver a focused beam of light that may penetrate somewhat better into the tissue than LEDs. However, everything is not equal. For an LED array with a power output of 100 Watts, you would only pay hundreds of dollars. For an equivalent power output laser that you’d have to expand to a very large treatment area with appropriate lenses, you’d pay tens of thousands of dollars. Laser and LEDs are different, but both are useful. LEDs are clearly better to deliver large amounts of energy into the body.

Can You Joovv Too Much?

Joovv: In your opinion, can someone use a Joovv too much? Third-party testing finds that when sitting or standing about 6” from a Joovv device, the average user will receive about 30-40 joules/cm2. In other words, at what point would using a Joovv become unproductive?

Dr. Hamblin: The key issue here is probably not energy density (J/cm2) but total energy (total Joules). Energy density is perfectly fine for discussing dosimetry for traditional laser therapy where a relatively small laser spot is focused on the tissue. However, for large LED devices like Joovv, the total Joules absorbed by the body is most important. In this case, many thousands of Joules will usually be an appropriate dose.

But keep in mind, there may be high responders (a few %), average responders (the majority), or low responders (a few %). The high responders are the ones that may get an “overdose”, but it won’t do them any permanent harm. Another consideration is that a person sunbathing for one hour (in the summer at midday in a temperate latitude, with UV protection) will absorb one million Joules of light energy. Therefore, over-using a PBM device is rather difficult.

Want to learn more about Dr. Hamblin?  Here's his more extensive bio:

Michael Hamblin, Ph.D., is a Principal Investigator at the Wellman Center for Photomedicine at Massachusetts General Hospital, an Associate Professor of Dermatology at Harvard Medical School, and a member of the Affiliated Faculty of Harvard-MIT Division of Health Science and Technology. He has published over 300 peer-reviewed articles on light therapy and is a member of Joovv’s scientific advisory board.

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