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.
