IT IS ALL ABOUT THE DOSE !
When choosing a therapeutic laser – the bottom line in laser therapy is “it’s all about the dose”, much the same way it is with antibiotics or NSAIDs etc. A low power Class 1, 2 or 3 laser will do the same as a Class 4 laser at the same wavelength, this is not disputed. But if the dose is calculated as x Joules/ cm sq and a Joule = 1 watt x 1 sec – then it is obvious the lower the watts produced the longer the time it takes to achieve a therapeutic dose. This is 100% what it is all about. So if you are looking at a non Class IV laser consider this – you need to treat a cat’s back – roughly an area of 30cm x 8cm = 240cm2. The therapeutic dose will be between 6-12 J/cm2, so let’s say 9 J/cm2 by 240cm2 = 2160 Joules required in total. 1 Joule = 1 watt of power for 1 second. Therefore if you look at Spectravet or Laserex lasers with peak continuous outputs of 500mW and 450mW respectively, it will take you 72 mins to treat that cat. Or you may be considering MLS laser like the Mphi Vet unit with maximum continuous power of 1.1 Watt which just sneaks it into the Class IV arena – that will take 32 mins to treat. However at maximum power Crane Medical Lasers will take 4 mins for the iPALM 9B, 3.6 mins for the CHEESE II 10B and only 2.4 mins for the Gbox 15AB. Look out if it’s a Shepherd!!
If you have a Class IV laser they have to be cooled to remove the extra heat generated by the diodes. This requires a major jump in both sophistication and cost to produce, which is the main reason why manufacturers stick with Class 3. They then try to get around it by pulsing, superpulsing or recommending point to point. The pulsing does not have any benefits over continuous, because it comes back to dose. So you must focus on average power output to be able to compare units. Point therapy in fine as long as you know which point to treat, and you rarely do. It would be fine for acupuncture, but not general practice. Say you’re treating an IVDD dog – where exactly are the specific points to treat? I just treat the whole area as a block – it won’t hurt the healthy tissue and it will help the unhealthy.
People who already own devices tend to say they are happy, otherwise they have to fess up that they bought badly initially. How many bits do you use that have better options available but you can’t justify throwing out the old one to get the new one. My dental machine is my case in hand – it just won’t die, meanwhile I covert the new high tech ones. So people with Class 3 will often endorse them. And at the end of the day – is a Class 3 therapy laser better than no laser? Absolutely. But is a Class 4 laser more efficient at delivering a therapeutic dose in a timely manner than a Class 3 unit? Absolutely.
I have a client who I helped to buy a Class 2 laser to treat his dog for chronic bilateral OA of the hocks. He treats one point on each hock, because we have X-rayed the dog and know exactly where the problem is. We have lasered this dog ourselves and got a brilliant response – BUT it requires weekly therapy to maintain it because it continues to do the activity it loves that caused the injury. He has little money but loads of time. So by spending about $900 on his unit he can laser his dog 2 times week for 20 mins per hock and get a very similar response to bringing it to us weekly for about 1 minute of therapy total. So you can get the same response with different Classes if you have the time. And as you are well aware – time is everything in vet practice.
AND THE WAVELENGTH
Wavelength is another point of disputation. For example the ActiVet Pro, Multi Radiance’s top liner includes the following wavelengths – Laser 905 nm, Infrared 875 nm, Red 640 nm, Blue 465 nm !!!. The best wavelengths for laser therapy are 980nm and 810nm,. This laser does not include either. 905nm is included as it is the first and very much the cheapest diode money can buy. 640nm is basically the red aiming beam found on most Class IV therapy lasers. 465nm is used by podiatrists to treat fungal nail bed infections (which your Class 4 will do anyway). 875nm – not sure about this, but I suspect they include it because it was cheap and having twice the number of wavelengths looks much more impressive. Consider this article Photodermatol Photoimmunol Photomed 2017; 33: 4–13 where the authors concluded “Near-infrared (800–830 nm) was found to be the most effective and widely studied wavelength range followed by red (630–680 nm) and 904 nm superpulsed light exhibiting beneficial photobiomodulatory effects on impaired dermal wound healing.” 980nm was not in this study, possibly because it is relatively new and more commonly found in veterinary literature. Incidentally K-Laser have more recently also gone down the let’s add more wavelengths to make our products look impressive and are now offering 4 wavelengths (660nm, 800nm, 905nm, 970 nm). As mentioned 660nm is an aiming beam, 800nm is not quite 810nm, 970nm is not quite 980nm, and there’s that 905nm again. Gigaa have taken the approach that you buy the laser you need for the purpose intended, and consequently manufacture lasers with wavelengths of 532nm, 635nm, 670nm, 810nm, 940nm, 980nm, 1064nm, 1210nm, and 1470nm.
I am not saying that any of these lasers will not work, of course they will and they can all produce trials and studies to support this. But just like choosing pharmaceuticals to treat infection or pain, you want the most effective drug (or wavelength in the case of lasers) given at the appropriate dosage (laser’s therapeutic dose). Will penicillin at sub optimal doses help at all, probably, but not as good as amoxyclav given at the recommended dose. Will low dose aspirin help with pain, probably, but not as well as meloxicam given at the correct dose.
AND THE INTENSITY
Finally, don’t forget spot size. The size of the therapeutic laser head will influence your speed of treatment – the larger the head the faster it is to cover any area given the output density is the same. But if you reduce the spot size with the adjustable heads that vary the spot size you will alter the intensity of the beam. Then you had better have a calculator and pie handy to recalculate all parameters. Using the Gbox 15AB as an example, 15 watts through the therapy hand piece with a spot size of 30mm diameter will slightly warm the tissues. However if you connect a 400um surgical fibre instead and set it on 2.5 watts, it will vapourise the same tissue and now it’s a surgical laser.
One thing that is very useful to have with all this stuff is a healthy degree of skepticism. You should go to http://aimla.org/ and look around for more info. The book they have shown there looks like a cracker and will be out soon. I had quite a good chat to both the editors at the WVC 2017 conference and it seems quite exhaustive in its content, and covers all these topics far better than I can.
The bottom line is that you could give a 10kg dog, 200 1mg aspirin tablets the size of uterine pessaries for pain, and you would help a little. Alternatively, you could give one small tablet (Spot Size) of a much more effective NSAID (Wavelength) at a high enough concentration (Power) to deliver the prescribed therapeutic dose (Joules), and provide a much simpler and more effective treatment. It really is that simple.