The following are some personal observations on the interplay of light and PD. Let me preface this message with the disclaimer that what follows is based solely on my personal observations and has not been subjected to the critical scrutiny of the research community. Based on empirical observation I would suggest that in PD there is an abnormality in either the perception or processing of motion and that this abnormality is dynamic. By this I mean that it changes with the levels of dopamine either in our brains or perhaps even more probably in the retina which is an organ rich in dopaminergic neurons. When PD people are undermedicated ("off") we have a decreased perception of motion and when medicated (especially when dyskinetic) we have a hypersensitivity to motion. These are not two separate pathologies but merely the same abnormality whose clinical presentation varies as a function of whether it is being seen in the presence or absence of dopamine. (The same could be said about akinesia and dyskinesia.) This hypersensitivity to motion is one of two categories of stimuli which tend to augment dyskinetic motion, the other is an autonomic (anxiety or tension) stimulus. If you have PD and tend to be dyskinetic you are likely to be extremely sensitive to motion sickness. If I go down to the playground with my son and ride on the swings I get motion sickness within a few seconds. If I am walking and dyskinetic my dyskinesia gets worse if I see the resulting dyskinetic apparent motion of objects as I walk past them or for that matter the dyskinetic motion of my own body. If one observes dyskinetic PD subjects walking they frequently will be seen carrying objects or putting hands in pockets to anchor their arms and decrease the amount of extraneous body motion to be seen. Objects on the horizon don't appear to move as much as objects we see peripherally. If you look at the horizon only, by looking through a long tube, dyskinetic walking is suppressed.. Our peripheral vision is programmed to only detect motion and as such is very sensitive to moving stimuli. This led me to begin experimenting with different color filters. I felt that if one could make the world appear monochromatic objects moving against objects would be less apparent. Furthermore, blue tends to create a kind of myopic effect. Also, color perception and the perception of motion are interrelated. While I have no scientific proof, clinically I believe I can demonstrate that wearing blue filters of the proper wavelength can dramatically facilitate the suppression of dyskinesia in a high percentage of PD subjects. The blue filter will also facilitate the suppression of autonomic (tension-anxiety) induced dyskinesia. (Incidently, if I wear my blue filters while using the swing I have no motion sickness problems.) The blue filter tends to normalize this hypersensitivity to motion. In order to be effective the filter need only cover one's peripheral vision - central vision can remain unobstructed. There are in fact a number of more effective ways to suppress dyskinesia (use of visual cues for example) but currently the blue glasses are the only currently available device which I would call in a socially acceptable form. In conclusion let me comment briefly on the other end of the spectrum - the undermedicated side. I have found that bright light especially when seen through a light yellow or amber filter can augment the effects of dopamine. If one has just cycled off and is akinetic it is much easier to walk towards a bright light than away from one. The closer the light source the greater the impact. Some researchers have speculated that the fixed, non-blinking stare of PD is a compensatory attempt to get more light to the retina.