Arguing with Lasers

When I am thinking about various pseudo-scientific treatments it frequently takes the form of a dialogue, or to be more blunt, argument in my head. Yes I talk to myself. 

So here’s a dialogue about Low Level Laser Therapy (LLLT).

But first, I work professionally as an independent physical therapist and strength coach. If you are interested in my services you can email me at: hirsch.sm@gmail.com. Or if you just want to support my blog you can buy me a KoFi

Actual Low Level Laser Therapy application – credit

In brief, LLLT is a passive modality used in PT that involves the therapist moving a wand over the injured area and the wand shoots a laser at your skin.

Me: The thing that strikes me about LLLT in the peer-reviewed, published literature is the fact that the articles don’t even contain a plausible hypothesis. 

Laser Enthusiast: Well, the laser delivers energy to the tissue. 

Me: Yes, but so does a hot pack. 

LE: A laser is different!

Me: Yes, and . . .

LE: It’s  a different kind of energy than a hot pack.

Me: It’s photons. The same thing as a lightbulb. Why can’t I just use a lightbulb?

LE: It’s focused.

Me: A lightbulb can have mirrors in front of it so that it’s just as focused as a laser. And not all lasers are focused. A laser is defined by being EITHER collimated or monochromatic, it doesn’t have to be both and the most widespread kinds aren’t collimated, so they have focusing lenses too. 

LE: But it’s also monochromatic, you just said that. 

Me: Sure. It’s all a narrow range of frequencies of light. What does that do?

LE: Well, the tissue reacts in a particular way, or something . . .

Me: When I point out that the published research lacks a clear hypothesis this is specifically what I am talking about. The paper will say we used such and such frequency of light but won’t explain why. 

This illustrates the importance of doing bench research before doing any animal or clinical trials. 

The first laser studies should have involved pointing lasers at petri dishes of cells and seeing what happened. Does a particular frequency stimulate a particular molecule? Does stimulating that molecule mean anything relevant? Does a specific frequency stimulate a particular cell type to do something relevant? 

And these studies needed to compare these measures to a good control condition like the same watt-minutes of a different frequency or of white light.

These are the types of questions that should have been answered first. These are the types of hypotheses that should have been tested in the research. But this is absent from the write-ups. 

LE: So what if we don’t know the mechanism of action. There are plenty of approved drugs that we don’t know the mechanism for. 

Me: Oh sure, that’s a valid point. But the standards for approving a drug require much more clear evidence of benefit than a device. I’ve talked about the low standard of evidence for medical devices before

LE: But the studies do show positive results.

Me: But are they well designed studies? And do they show clinically relevant results?

What’s the control group in these RCT’s? Usually it’s the same laser wand without the laser turned on. While the control group may not realize they are in the control group because they feel nothing, they may suspect they are in the control group because they feel nothing. But the experimental group KNOWS they are the experimental group because they feel it get hot. So hot that it can cause burns if not used properly. 

When both the control and experimental group have a pretty good idea which group they are in then the study isn’t particularly well blinded. This influences reported results. Enough to produce false positive results. 

A good control group would be standard of care. In the same way that approval for a new pain-killer would require comparison not merely to a sugar pill but also to another standard pain-killer. If a drug company wants to sell a new pain-killer and it’s not better than Tylenol but it’s also more expensive and dangerous then it doesn’t matter if it’s better than a sugar pill, it’s not getting approved. 

LE: Well, if patients think it’s working isn’t that good enough?

Me: No.

This is what’s important about the comparison to a hot pack. The hot pack can cause burns, it’s true, but preventing that is incredibly easy. Like, you let the undergrad clinic slaves apply hot packs (true story). 

They also don’t require a physical therapist to sit there and apply the treatment. You just put the hot pack on and walk away. But the LLLT requires my doctorate educated time to sit there and constantly wiggle the wand to keep it from burning the patient. My time is expensive. 

Plus, the hot pack is something the patient can do for themself. There are a wide variety of kinds they can purchase. There are long lasting ones using the same kinds of chemistry as a chemical hand warmer. There are ones that can be microwaved for instant relief. There are electric heating pads. And they are all cheaper than a PT clinic Co-Pay.

Hot packs are really convenient for the patient. They improve the patient’s sense of ability to control and manage their own condition. They improve their self-efficacy. These are all good things for the patient long-term. 

While the laser (and any other passive treatment) creates the idea that the patient needs an appointment with the therapist to feel better. It may be profitable business but it’s not in the best interests of the patient or the cost of our healthcare system. 

LE: But you haven’t really addressed whether or not the lasers work. 

Me: How well they work needs to be put in perspective. Before we can conclude that the laser is a better treatment for the patient it has to demonstrate that it is SO MUCH better than a hot pack to justify the higher cost, higher risk and patient’s loss of control. That means big effect sizes. 

Statistically significant effect sizes don’t even matter to me. As I discussed in the VR for Back Pain article what matters to a patient are clinically significant effect sizes. And these effect sizes would need to show a clinically significant difference to hot packs, not merely to an inert control. 

Any researcher can get a statistically significant result from the “gee whiz!” factor from using lasers but that doesn’t prove the effects are real. 

So, no, lasers are for tag, not physical therapy.

The good kind of arguing with lasers – credit

Author: Steven Hirsch, DPT, CSCS

Physical therapist, strength coach, historical fencer.

2 thoughts on “Arguing with Lasers”

  1. LLLT doesn’t give off any heat… They are class III lasers and the “light” you see is just LEDs to show that it is emitting the laser therapy. Class IV lasers give off heat like the lightforce laser that has gained more clinical use as of late. Have to differentiate between the two.

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    1. As I state in my post, LLLT emits photons. The class of laser is irrelevant to whether or not they emit photons – laser are photon emitters. Any photon that is absorbed by a material will heat that material up. It’s how microwaves and heat lamps work. It’s very basic physics.

      I’m fully aware that the light on an LLLT wand is not the active light, and is instead simply an indicator. But that’s irrelevant, as I describe above.

      Most, (maybe all – I don’t know every product) use infrared frequency light. This is noteworthy specifically because of the fact that IR is almost entirely absorbed by the target tissue. Which is to say that it is an efficient way of heating the target tissue.

      All LLLT heats the target tissue. And that’s all they do. No evidence has shown other effects.

      I don’t have to differentiate between classes of lasers. And you did not address any of the valid reasons for my opposition to LLLT.

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