The “Class IV” myths

By Jan Tunér

Several manufacturers offer lasers in the Class 4 (IV) group of lasers; that is lasers emitting more than 500 mW. This classification is a bit problematic, because it is possible to start a fire with a 30 mW 808 nm laser and to biostimulate with one of 10 watts. It is primarily a matter of optics and beam size. As we all know, we can start a fire by focusing the light from the sun through a magnifying glass.

The very strong biostimulation lasers have various techniques to overcome the heat. The most common way is to use a wide aperture, thereby lowering the power density. This may or may not be combined with water and air cooling. The beam can also be pulsed to allow for heat dissipation (which simply reduces the output power for which you’ve paid a fortune!)

Very strong lasers may have their place in phototherapy, but a problem is the marketing and the tricks used. Most of these manufacturers claim that their strong lasers have a greater depth of penetration than the “weak” 3B lasers. However, the opposite is true. Since there is so much heat, the probe has to be used at a distance or with a constant movement. Keeping it at a distance means that a considerable amount of the energy is lost through reflection, and keeping it in movement means that the energy has to be introduced over large areas, even if the target is small. And it takes a lot of attention to not cause burns. The Companion laser is one of the most blatant liars in the field, since the company claims that their many-watts-laser of 980 nm has a better penetration than a 500 mW 808 nm laser. It is common knowledge that 980 nm has a lower penetration rate than 808 nm. The very best penetration is actually obtained with the superpulsed 904 nm, with 808 nm in second place.

These lasers arrived on the market before there were any publications. A few are now appearing and let us have a look at some!

1. Roberts D B, Kruse R J, Stoll S F. The Effectiveness of Therapeutic Class IV (10 W) Laser Treatment for Epicondylitis. Lasers Surg Med.2013; 45 (5): 311-317.

Roberts evaluated a dual wavelength (980/810 nm) class 4 laser with a power output of 10 W for the purpose of determining the efficacy of class 4 laser therapy in alleviating the pain and dysfunction associated with chronic epicondylitis. Sixteen subjects volunteered for laser therapy, or an identically appearing sham instrument in a randomized, placebo-controlled, double-blinded clinical trial. Subjects underwent clinical examination (pain, function, strength, and ultrasonic imaging) to confirm chronic tendinopathy of the extensor carpi radialis brevis tendon, followed by eight treatments of 6.6 +/- 1.3 J/cm2 (laser), or sham over 18 days. The exam protocol was repeated at 0, 3, 6 and 12 months post-treatment. No initial differences were seen between the two groups. In the laser treated group handgrip strength improved by 17 +/- 3%, 52 +/- 7%, and 66 +/- 6% at 3, 6, and 12 months respectively; function improved by 44 +/- 1%, 71 +/- 3%, and 82 +/- 2%, and pain with resistance to extension of the middle finger was reduced by 50 +/- 6%, 93 +/- 4%, and 100 +/- 1% at 3, 6 and 12 months, respectively. In contrast, no changes were seen until 12 months following sham treatment (12 months: strength improved by 13 +/- 2%, function improved by 52 +/- 3%, pain with resistance to extension of the middle finger reduced by 76 +/- 2%). No adverse effects were reported at any time. (Shortened abstract)

The authors write: “These findings suggest that laser therapy using the 10 W Class 4 instrument is efficacious for the long-term relief of the symptoms associated with chronic epicondylitis. The potential for a rapidly administered, safe and effective treatment warrants further investigation.” This conclusion must be questioned. Not only that a 10 W laser poses a much higher risk of burning and eye injury and is more expensive than a class 3B laser – a Class 3B laser is quicker! The high output forces a sweeping motion or irradiation from a distance, thereby causing a lot of energy loss at the deep target. The time spent was 5 minutes, which is more than a conventional class 3B session for this condition. With a 3B laser in firm contact over tender points and a sweeping motion over the actual superficial condyle, more energy can be applied in 2-3 minutes. The authors of the paper above swept over an area of 45 cm2. By spreading the light over a large area, using a wide beam area and irradiating from a distance, the dose became 6.6 J/cm2 and the power density only 22 mW/cm2, which is very low. 3.000 J, but is “more” really better? Irradiating in contact with 10 W is not possible, but with a 3B laser in firm contact, an optimal penetration is achieved and less time is required. Yes, it was a 10 Watt laser and yes, 3,000 joules was delivered. However it had a very large beam area and treatment was delivered over a very large area (45cm2) in a “painting fashion”. The fluence (dose) was 6.6 Joules/cm2 and the power density was a tiny 22mW/cm2, consequently treatment time was a hefty 5 minutes.

2. Conforti M, Fachinetti G P. High power laser therapy treatment compared to simple segmental physical rehabilitation in whiplash injuries (1 degrees and 2 degrees grade of the Quebec Task Force classification) involving muscles and ligaments. Muscles Ligaments Tendons J. 2013; 3 (2): 106-111.

Conforti [2337] conducted a short term prospective randomised study to test the effectiveness of a multi wave “High Power Laser Therapy (HPLT)” versus conventional simple segmental physical rehabilitation (PT). The authors identified 135 homogeneous patients with whiplash grade 1 – 2 of the Quebec Task Force classification (QTFC). Group A (84 patients) was treated with HPLT, Group B (51 patients) received conventional simple segmental physical rehabilitation (PT). During the treatment period, no other electro-medical therapy, analgesics or anti-inflammatory drugs were allowed. All patients were assessed at baseline (T0) and at the end of the treatment period (T1) using a VAS, (T2) the date of return to work was registered afterwards. There was a reduction in VAS pain scores at T1. Group A (VAS = 20) Group B (VAS = 34.8). Laser treatment allowed quick recovery and return to work (T2). Group A after 48 days against 66 days of Group B. (Shortened abstract)

This promising study is short of details and is unclear in the reporting of several parameters, but obviously a 12 W laser with three wavelengths within 780-1100 nm was used, Parameters are not included in the abstract. Power density is reported to be 7.5 W/cm2, five points irradiated for 40 seconds each, 20-30 J, using a cooling system to keep temperature rise below 2.5C. The authors claim that the high power increases penetration, which of course is incorrect. The laser treatment was performed with simultaneous micro-rotating electrical fields, which makes the actual LPT effect difficult to evaluate. A class 3B laser of 500 mW would require 60 seconds to deliver 30 J.

So what is the “best” output of a biostimulative laser? Well, which is the best car? Are you a travelling salesman, a retired person using it for local shopping, a family of 7 individuals, a fan of fast driving, are you experienced or did you just get your license? And how are the roads in your area? And the climate? Same thing for lasers. There is no “one-size-fits-all” machine.

Certainly lasers of high output are useful for acute pain conditions and large muscular areas. But do we ever really need more than 1000 mW? Some practitioners will say they do, but the great majority of users do not. Actually, a lot of what laser therapists do is to reduce inflammation, and that requires low power and long time. Applying high energies decreases pain temporarily but prolongs the inflammatory process.

A common feature in the papers above is that the investigators may have been skilled, but not knowledgeable in the LPT field. So they have been in the hands of their advisors – the manufacturers. This is reflected in the paper, where parameters are not documented in the abstract (making PubMed evaluation impossible) and even in the full paper. And in the list of references, oranges and apples are compared.

The “Class IV” lasers are expensive and the risk of optical and thermal injury increases dramatically. Are they worth the price, and are they really needed?

Like the man in the bar of the Titanic said: “I asked for ice in my drink, but isn’t this a bit much?”