One would be looking right at it. Also. it rather thoughtlessly is not around when one needs it. That is not saying, however, that this is the only way that light may be important in PD. Consider the blue light effect, for example.

Thus far, I suspect that I am using a strong light as a tool to adjust some unknown force in my endocrine system or neurotransmitters. I am watching for a potential problem if raw material runs low for, say, dopamine due to forcing its production or something. No reason to expect it, but just possible.

Given the that the pineal gland is still mysterious, anything could be happening. It might even be that it is not working via the eyes at all, but through receptors in the skin of the forehead connected to the pineal. A couple of years ago they discovered similar receptors in the skin back of the knee which acted to relieve jet lag. Why not?