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What Two Factors Impact Red Light Therapy Effectiveness

When it comes to red light therapy, the distance from the diode plays a critical role in determining the power delivered to the target area. As light travels away from the source, it gradually loses intensity due to scattering and absorption.

As the diode is moved farther away from the target area during red light therapy, the intensity of the light, measured in milliwatts per square centimeter (mW/cm²), decreases. This decrease in intensity follows the principle of the inverse square law, which states that the intensity of light diminishes as the square of the distance from the light source increases. So, as the distance from the diode increases, the intensity of light decreases rapidly.

This phenomenon is a fundamental characteristic of light propagation and applies to various light sources, including those used in red light therapy. The reduction in light intensity has important implications for the efficacy of red light therapy. As the light becomes less intense, the amount of energy delivered to the target tissues diminishes. Consequently, the cells may not receive the optimal dosage required to trigger the desired biological responses.

This is important, as when a manufacturer indicates they have an irradiance of 110mW/cm2… that sounds very impressive, as experts have indicated healing happens at a minimum of 30mW/cm2. Yet as we take a closer look, when the target area is impacted by the red light therapy, because of

1. The distance from the diode and

2. The thickness of the material used between the diode and the body or target area

…and as a result, the actual red light impacting the target may be at 15mW/cm2 for example, which provides virtually NO healing or therapy.

In this illustration, we are showing both Distance and Thickness of Overlay. In this first image, going from left to right, you’ll see the measurement of 129mw/cm2 directly on the diode. Next to the right, you’ll see the same diode, yet measured just 1inch from the diode and the measurement went from 129mw/cm2 to 2.2mw/cm2… then the next reading is a full 2 inches from the target and the reading drops to .4mw/cm2. So you can see how distance affects the impact or therapeutical value of red light therapy.

This next series of images deals with the addition of 1/32 inch of poly carbonate, which is lays directly on top of our diodes… and we’ll also add the distance factor as well. You’ll see here in this first image on the left, a diode which measured 129mw/cm2 with a 1/32 clear poly carbonate in between the diode and the measurement tool comes in at 89.9mw/cm2., then measured at 1 inch away with the same 1/32 poly carbonate cover, and the reading is a dismal 1.9mw/cm2. At 2 inches, the reading is .4mw/cm2.

The good news, Body Balance uses the 1/32 poly carbonate on our OvationULT bed. The bad news is, the other beds on the market typically use a 1/8 inch poly carbonate cover.

Let’s take a look at how the thicker poly carbonate cover affects the mw/cm2. You see the first reading from the 129mw/cm2 diode is 32.5, then at 1 inch it drops to 1.6mw/cm2, and at 2 inches the reading drops to .4mw/cm2 In summary, manufactures may have lights or diodes which emit a irradiance of 110mw/cm2, yet between the distance from the diode and the thickness of the cover, that’s why you see the disappointing readings in the red light therapy market today. Remember in order for healing or therapy to occur, the area of focus be exposed to at LEAST 30mw/cm2.

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