When you look through a telescope at a distant planet you are experiencing the photons of light bouncing off the planet but not the planet as it is in itself; that is shrouded in mystery. Similarly, when I look at a person I am not experiencing them as they are in themselves but only the light that is reflected off them. In other words, experience is indirect and mediated by physical phenomena (e.g. light, sound waves, stimulation of nerve cells etc) unlike the object being observed (e.g. the human body is not a photon of light). Objects in themselves can never be known because knowing requires a knower with an indirect point of view; to know things in themselves means viewing without taking up point of view, which is impossible. Objects are always experienced as a reflection of their true nature.
What about when I look at myself and with self-awareness recognise myself? Isn’t that experiencing myself as a thing in itself? The experience of my body is still indirect and mediated by physical phenomena; for example, visual experience of myself is mediated by light. If I close my eyes I still sense my body as a possession of myself, but this is dependent on sensory input from my body; I cannot know myself without such input and the point of view constructed out of it. Therefore, self-awareness is from a specific point of view, only the sensory input is internal and external; we have privileged access to inner sensations but this is from a specific point of view (our own) and never as a thing in itself; viewing must be from a point of view. It follows that we will never fully know ourselves despite our self-awareness.
Parkinson’s is a disease with a physical manifestation that overlays conscious control with stereotypical movements (e.g. tremor, blank facial expression etc). In a sense it distorts the reflection of the person beneath the symptoms to those around them; the photons of light bounce off the person at the wrong angle. The viewer of a Parkinson’s sufferer, including the sufferer herself, has to readjust, filter out the distortion, to see a clearer reflection of the person; they are not just a reflection of the disease.