Light Therapy for Parkinson's Disease

Melanopsin cells are intrinsically photosensitive retinal ganglion cells, meaning they can detect light on their own, unlike rods and cones which rely on those cells to send signals.

 

Their main function is regulating our circadian rhythms, which is our internal clock and therefore impacts our sleep-wake cycles. They also control the pupillary light reflex, making our pupils constrict in bright light, and influence our mood.

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they send information to various parts of the brain, primarily those responsible for non-visual functions. One of the main connections is to the suprachiasmatic nucleus (SCN), which acts as the body's central circadian clock. Other connections include the pretectum, involved in the pupillary light reflex, and the lateral geniculate complex, which plays a role in visual processing.

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Melanopsin cells are most sensitive to blue light, which is prevalent in white light, e.g. bright sunlight, and is more present in morning light. 

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Afternoon light, especially as it gets later, tends to have a lower blue component and more of a warm, yellowish tone. Using other mechanisms, this less stimulating light sends cues to your body that it's time to start winding down.
 

Blue light from screens typically has a much higher concentration of blue wavelengths compared to the full spectrum of light found in sunlight, especially morning light. This concentrated blue light from screens can be more disruptive to your circadian rhythm, particularly if you're exposed to it later in the day.

Melanopsin cells and PD

Research indicates that people with Parkinson's disease often have dysfunction or degradation of their melanopsin cells, which can contribute to sleep disruptions and circadian rhythm issues.

Degradation, in the context of melanopsin cells in Parkinson's disease, refers to a gradual loss of the cells structure and function. This can lead to fewer melanopsin cells remaining, and those that are left may not function as effectively impacting their ability to detect light properly.

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