Vision and Parkinson’s

CONSCIOUS AWARENESS is a product of how we see. Our personal sense of REALITY is a result of brain processing. One person’s brain does not always process information the same as another person’s brain. When someone has suffered an ABI (Acquired Brain Injury) such as Parkinson’s disease, the brain’s processing of visual information changes; for example, the perception of space changes.

In a book called “Mind Time” by Benjamin Libet, published in 2004, the publisher wrote, “our subjective inner life is what really matters to us as human beings…and yet we know relatively little about how it arises.” Over a long and distinguished career, Libet has conducted experiments that have helped us see, in clear and concrete ways, how the brain produces CONSCIOUS AWARENESS. Libet’s experiments reveal a substantial delay or lag between the unconscious awareness and the conscious awareness of our perception. If all conscious awareness is preceded by the unconscious process … then unconscious processes initiate our conscious experiences. In other words, there is a time lag between when we really see things and when we are aware of seeing something. The amount of this time lag can affect our perception of reality, and in this way, perception can differ between people.

Merrill Bowan, O.D. writes, “We perceive REALITY…as though all inputs to the brain were simultaneous.” This is hardly true…We know now that sensory signals are actually processed at different speeds, with auditory input being     processed far more quickly than motor or kinesthetic inputs. Vision is processed in widely separated areas of the brain and color is processed the slowest of all visual qualities…”

Many patients with acquired brain injury report experiencing COLOR SLIDING off of moving objects. This might look like windshield wipers having a dark streak following them, or seeing car lights at night as if in a time-exposure picture. There is some speculation that the excitotoxicity of an acquired brain injured patient “unbinds” the normal synchrony of perception.

Our experience thus far is that the fitting of PRISMS by the neuro optometrist on these patients not only puts the body into better balance, improving gait and cognition, but also results in a normalization of the “COLOR SLIDING”. The prisms may improve this symptom by functioning as neural filters that slow down the excitotoxicity action (causing all color information to fire in the brain at the same time), either physiologically by dopamine release that neutralizes glutamate, the suspected culprit, or by other neurophysiological changes.

People with Parkinson’s are encouraged to see a neuro optometrist for evaluation and remediation of defective vision anomalies. Learn more at

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