The light therapy equation

Since the discovery that specialized therapeutic light is one of the most effective means for treating Winter Blues and other circadian related problems, scientists have been searching for the best way to use light to help sufferers recover as quickly as possible.

Light alone is not enough

Although researchers have found that specialized light is the best way to treat circadian rhythm problems, they quickly discovered that just using a full-spectrum, 10,000-lux light was not enough. In fact, using this light at any time of the day could cause more harm than good, and best time to use the light was different for most people. Their efforts to find the proper dose response relationship have resulted in the light therapy equation.

The most effective response

The light therapy equation is critical because everyone's internal body clock is different and reacts differently to light therapy. Knowing what time of day and how much light to use can mean the difference between responding in a few days instead of not responding or causing the problem to become worse. For example, someone with an advanced circadian rhythm will compound his/her problem by using morning light. The light therapy equation solves this problem by determining the proper time of day, intensity and duration of light for each individual.

Light therapy equation

[

Y =

A1 - A2 _____________ 1 + (X/X50)P

+ A2

]

ƒ   T • D

Y = Fluence-response curve formula
A1 = Theoretical initial Y-value for curve
A2 = Theoretical final Y-value for curve
X 50 = X-value of curve midpoint Y value
P = power function describing curve slope
T = Time determined by circadian phase-shift algorithms
D = Duration of exposure

Circadian Rhythm Assessment Test

The Circadian Rhythm Test uses the light therapy equation to determine the most effective time to use specialized light. The test identifies what is happening to an individual's body clock and compares his/her rhythm to a normal circadian rhythm. This comparison allows the test to determine the effective time to use light as well as the duration of light exposure.

Personalized Treatment Schedule

The light therapy equation also allows the test results to create a personalized treatment schedule. Using light according to this schedule will quickly shift an out of sync body clock back to a normal position. This schedule also helps one avoid problems resulting from using the light at the wrong time of day. Once the body clock is synchronized, the amount of daily light exposure can be reduced by as much as half.

Using the correct light

While it is true that standard bright light (full spectrum or 10,000 lux) may improve mood, there is a vast difference between using these lamps and yielding an effective response. Current research shows that specific wavelengths of light are responsible for shifting circadian rhythms and causing a neurochemical response. In fact, studies show this bandwidth to be five times more effective than all other wavelengths combined. Through a National Institute of Health research grant, Philips (formerly Apollo Health) has helped determine the effectiveness of this bandwidth of light. This specialized bandwidth is known as BLUEWAVE and is part of our BRITEWAVE Technology. The combination of specialized BRITEWAVE light, correct timing and duration of exposure ensure the quickest and highest quality response possible.