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Justin Strahan

Measuring the Power of Light Therapy Devices

If you’re trying to find the best light therapy device for you, there are a lot of factors to consider: the design, ability to customize the device to your specific treatment needs, warranty & service, and the power & energy output. The list certainly doesn’t stop there, but the last onepower & energytends to be the most confusing.

This article explains how power is measured for light therapy devices.  We’ll break down what measurements are the most important and what people should look for from manufacturers to accurately compare devices based on their power and effectiveness.

The Basics of Measuring Light Power

In the world of light therapy—or photobiomodulation (PBM)— irradiance measures power per unit area, typically defined in milliwatts per square centimeter (mW/cm2). Another way to think of irradiance is the rate of energy delivered. The total amount of energy delivered per area during a light therapy treatment is measured in Joules/cm2. This is calculated by multiplying the irradiance by the treatment time in seconds, divided by 1000.

For example, if the irradiance of a device is 17 mW/cm2, and the treatment time is 5 minutes, the calculation is as follows:

17 mW/cm2 x 300 seconds / 1000 mW/watt = 5.1 joules/cm2

Key Variables to Consider

The power of a light therapy device—or the effectiveness of a light therapy treatment—is more complex than just a measurement of irradiance.  There are several other factors that affect the overall success of the therapy. Some of the key variables include: the coverage area on the body, the session time, and the distance between the device and the person using it.

The Challenge for Consumers

Light therapy is growing in popularity, and more and more people are trying to measure light energy to either compare devices or to determine the proper dosage.  This has led to the common practice of using solar meters, such as the Megger PVM210, to measure light intensity. Inexpensive power meters like these can be somewhat useful for basic comparisons, but unfortunately, they aren’t sophisticated enough for accurate readings of power output. For example, holding the meter at an angle or between LEDs can lead to some pretty inaccurate readings.  This leaves most people to rely on what a manufacturer tells them, and that’s where things can get even more confusing.

Lack of Industry Standardization

Measuring the irradiance of devices is further complicated by a lack of standard measuring practices within the light therapy industry.  Too often, researchers don’t publish major variables such as the size of the treatment area, treatment times, and the methods used to measure power output of the devices used.  This presents an obvious challenge when comparing dosages across clinical studies.

How Other Light Therapy Manufacturers Measure Power

Because of the lack of standardization, manufacturers use a wide range of methods when presenting the power output of their devices.  Some list a simple wattage rating of the product, or perhaps a maximum irradiance number, but the result has always been the same: consumers don’t have an easy way to accurately compare devices.  Here at Joovv, we’ve always attempted to provide useful information to help consumers make an informed decision. But due to an increasing number of questions on this topic, we felt the need to provide even more clarity when it comes to properly measuring the effective output of light therapy devices.

How Leading Medical Researchers Measure Power

We consulted with Dr. Michael Hamblin, widely considered one of the world’s leading researchers in the field of light therapy, on how his Harvard Medical School program measures light power:  

“To accurately measure the irradiance of both laser and LED light therapy devices, we use Ophir Nova meters,” said Dr. Hamblin. “The photodiode and thermopile sensors allow us to precisely determine power in mW/cm2.”  

Unfortunately, a professional power meter like this isn’t accessible for consumers as the cost runs several thousands of dollars.  

More so, measuring irradiance with an expensive tool like this doesn’t provide the whole picture.  A better way to compare light therapy output takes into consideration the entire area being treated rather than a single point of measurement.  Researchers understand that the total amount of light energy delivered provides a much better comparison method:

“Total light energy is the most accurate and comprehensive way to measure the power of light therapy devices and treatments,” said Dr. Hamblin. “If you only account for irradiance—versus how much total energy a device delivers—you miss the larger picture of how light therapy positively benefits the person using it.”

With Light Therapy, Size Matters

Since the total light energy is what really matters, it’s clear that the area of the treatment shouldn’t be ignored. If you remember anything, it should be this: the size and uniformity of the treatment area are critical to measuring the power and effectiveness of a light therapy device. Targeted treatment areas can work wonders for a specific area of the body, but to experience the full range of health benefits from light therapy, it’s best to treat the whole body with a uniform, consistent dosage. This simply isn’t possible with a small device.

Testing & Comparing Light Therapy Devices

By now, it should be clear that total light energy is the best way to compare devices. The next question is this: what’s the best way to measure total light energy?  While there are various methods to accomplish this, the most accurate, unbiased way is to use an independent certified laboratory.  We believe this is the best way for manufacturers to provide useful specifications for consumers, which is why we contracted ITL (Independent Testing Laboratory) to conduct a series of radiometry tests on our devices along with a few other light therapy products available in the marketplace.  

The chart below displays the certified testing results showing the total energy output in 10 minutes, the total light output power, and the surface area for each device.

 Comparing Power of Joovv Versus Other Light Therapy Products

Dr. Hamblin sums up it well, “When you look at total energy and total power, you can see that the Joovv Solo actually delivers almost twice as much energy than Device A, while the Joovv Elite delivers almost ten times as much energy as Device A. Device B is clearly inferior to all the others, and shockingly, based on the data, the Joovv Elite is almost a staggering 100 times better.”

The graphic below shows how the Joovv Solo matches up with other light therapy brands. As you can see, a Joovv Solo gives you far more total energy output, and it covers a much larger surface area. Device A & Device B are Joovv alternatives, but they aren’t capable of providing the full coverage and total energy needed for optimal light therapy results.

Difference of Joovv Power Versus Other LED Light Therapy Products

Conclusion: Coverage Area and Energy Output are Incredibly Important

To determine the effectiveness of a light therapy device, you need to account for 3 things:

  • The size of the coverage area;
  • The total energy output; AND
  • The total energy absorbed by the body over the treatment session.

The only way to get accurate and unbiased specifications for these critical measurements is through certified testing from an independent laboratory.  As an industry leader, we fundamentally believe this type of information will give consumers the best chance at making an informed & educated decision when it comes to choosing a light therapy device.

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