Red lights and lasers, oh my!

Humphrey has benefitted from at-home red light therapy for a couple of years so far. It allows him to do his impression of a prawn, while also generating noticeable improvements to his skin and coat, and some help with joint injuries. We've posted about it before. 

Until very recently, Humphrey had only used an at-home unit of near-infrared LED lights that were inexpensive and not particularly strong.

A couple of weeks ago, he had in-office, medical-grade low-level laser therapy (LLLT) which is similar to the red light treatments, but much stronger. The results were noticeable on the first day.

This caused us to look a little further into the different types and strengths of these products. It has  been confusing! First, the vocabulary is a whole thing.

• red light - a wavelength of light that the human eye sees as red ranging from 620 to about 750 nanometres (nm). The 650 to 680 nm range is best for topical therapy (skin, hair)
• near infrared - the closest wavelength to visible red within the red spectrum ranging from 780 to 2500 nanometres (nm) -but the human eye doesn't perceive it. Wavelengths in the 850-880 range are used for deep tissue and muscle therapy.
• low level laser therapy (LLLT) - a general term referring to the use of any range (not just red) of wavelengths for therapy
• photobiomodulation - a general term for therapy that uses light sources (LED, laser, etc), not limited to red

Here's how red lights work: light photons are absorbed by mitochondrial chromophores in skin cells. This activates electron transport, adenosine triphosphate (ATP) nitric oxide release, blood flow, and various signaling pathways. When the cells start working, they heal faster, and produce collagen (which is decreased with age), and in some cases growth (such as hair growth) is stimulated.

Red lights and lasers have a number of different factors that dictate what they can be used for, and how quickly and well they achieve desired results.

Wavelength

The first factor is wavelength, measured in nanometres (nm), described above. To reiterate, wavelengths of about 620nm to 680nm will work on skin and hair and will be visible as red to the human eye. Wavelengths of 850nm to 880nm are for deeper tissue (muscles, ligaments) and will not be visible to the human eye. Most mass-market devices offer both of these wavelengths. 

Density

Next is power density or the intensity of light coming from the diode (sometimes called irradiance), measured in milliwatts per square centimetre (mw/cm2). An inexpensive device will have lower density, meaning the the red light will dissipate before  hitting the targeted part of the body. For example, the inexpensive bulb Humphrey has been using from Amazon has a density of 98mw/cm2 at 6 inches from the body. Studies will generally aim for a density of 200 mw/cm2.

Basically, the closer the device is to the target area, the stronger the density will be. 

FDA Classification: 1 through 4

Laser and LED devices are classified 1 through 4. Most at-home lasers are classified as 2 (and therefore require more contact time), whereas medical use therapeutic lasers will be classifications 3 and 4. 

Light Source: LED versus Laser

Medical-grade devices often (but not always!) rely on lasers for the source of light, while at-home devices are usually LED diodes. As of 2018, no LED-to-Laser direct comparison studies had been conducted. However, this excellent 2018 meta-analysis (with scrollable summary of studies included) suggests that LED has the potential to effective, thought its output is less coherent and targeted compared to a laser. LEDs have the benefit of being safer (since a laser requires goggles and could harm the eyes).

Humphrey has some big LLLT/red light decisions to make. Should he continue in-office treatments, which are quick and effective, but extremely expensive? Or should he splurge on a more expensive LLLT device that purports to be a Class 2 or 3B laser for at home use - which will be more cost effective since the price of a device is as low as 2 or 3 in-office treatments?

UPDATE:

We got  the least expensive LLLT laser from Amazon, and we believe it was worth every penny. We use it for 30 minute sessions - works on humans' sciatica as well as Humph's problems.