apdaparkinson.org published the following on their website:
Light therapy, or the use of light as a treatment for disease, is being investigated in many neurologic conditions including as a treatment for some of the symptoms of Parkinson’s disease (PD). Light therapy encompasses a large category of treatments involving different types of light and delivery systems. More research still needs to be done to figure out exactly what type of light therapy works for which symptoms of PD.
There is a very long list of variables to consider when thinking about how light can be delivered as a treatment and each variable could affect the light’s therapeutic potential.

What part of the light spectrum is being used?
Three wavelengths of light therapy are being considered for Parkinson’s disease:

The full spectrum of light (also called polychromatic light or white light)
Near infrared light (NIR in the wavelength range of (Phone number can only be seen by the question and answer creators) nanometers)
Blue light (wavelength range of 460-480 nanometers) – this light is thought to be most effective to influence the body’s own biological clock
How is the light being delivered?
In studies using white light, the eyes are used to detect the light. The light is therefore delivered via a lightbox or a screen.

Near Infrared Light (NIR) is not in the wavelength range that is detectable by eye. It is thought that to be used as a therapy, it needs to be delivered more directly to brain tissue. Therefore, other delivery methods have been devised.

Additional delivery methods include:
Via a helmet containing light sources that is worn on the head – the light is meant to penetrate through the skin and skull Intranasally Via a light-emitting device that is implanted in the brain
What is the brightness of the light?
Many clinical trials for light therapy used Lux levels in the 10,000 range. Light brightness per area is measured in Lux. A moonless night would register 0.0001 Lux. A very dark overcast day would register 100 Lux. Full daylight (but not direct sunlight) would register 10,000 Lux.

What is the length of a session of light therapy?
For light therapy to be feasible to incorporate into a person’s day, a practical amount of time spent in front of the light needs to be selected. Past trials have used times ranging from 30 min to 1.5 hours a day.

Please see the website for more info,
Maria

THanks Luka 53!

Thanks Bruce

An address for more info is;
https://www.apdaparkinson.org/article/light-the...