Written by: Dr. Caitlin A. Bender, OTD, OTR/L
Dopamine’s Role
As humans, vision is our dominant sense, with research suggesting that up to 70% of the entire body’s sensory receptors are located just within our eyes. This means vision is heavily relied upon when engaging in everyday tasks. As we age we naturally experience visual changes that may impact our ability to complete these functions, but Parkinson’s Disease, traditionally characterized as a movement disorder, may also play a role. Dopamine is a critical neurotransmitter involved in coordinating complex movement patterns, and is the primary neurotransmitter affected by Parkinson’s Disease. While dopamine doesn’t directly produce ocular movement, it does help to regulate saccadic eye movements and visual target selection, resulting in our ability to clearly focus on a specific point. Dopamine is also suggested to be involved in the function of the retinas, a tissue within our eyes that is key for visual processing through the perception of light, color, and other fine details. The impairment of these visual functions are associated with risk of falling and may impact overall independence; this may be intensified further for people with Parkinson’s Disease, who may use visual cues to compensate for other difficulties associated with the disease.
Reasons for Visual Difficulties with Parkinson’s Disease
Eye Movement
Dopamine may be associated with coordinating larger scale movements, but it also manages our smaller, precise movements required for visual function.
Saccadic movements, the rapid jumps your eyes complete as you shift visual targets, may be slow with Parkinson’s Disease, and may make tasks such as reading difficult.
Vergence eye movements, the small coordinated adjustments your eyes make to keep targets in focus, may be impacted and result in double vision, as well as difficulty reading.
Reduced Blink Rate
Dopamine is associated with our spontaneous eye blink reflex, tear deficiency and bradykinesia. This results in people with Parkinson’s Disease often blinking far less than average. This can further agitate visual function by causing dry eyes, irritation of the eyelids, and potential visual deterioration.
Sensory Changes
Retinal function is reliant on dopamine, and can be impacted as a result of Parkinson’s Disease. This can lead to loss of contract sensitivity and make distinguishing colors more difficult for those with Parkinson’s Disease.
The retina is involved with managing the light captured within the eye, and dysfunction may lead to light sensitivity. This retinal function also modulates our circadian rhythm, which is our internal clock that determines our wake/sleep cycle, digestion, and body temperature.
Strategies for Managing Visual Impairments
General tips:
See your ophthalmologist regularly for an eye examination. Visual impairments are associated with a higher risk for falls. Managing visual health is key to maintaining safety and overall independence.
Special prism eye glasses may be helpful for alleviating double vision, however you can also discuss with your doctor two separate prescriptions for your glasses, one for reading, and one for distances, to reduce symptoms.
Bifocal and progressive lens wearers should be cautious when moving up and down stairs since adjusting to these with compromised depth perception can be difficult, and increase the risk for falls.
Apply a warm, moist compress for eyelid irritation, and artificial tears for dry eyes.
Visual impairments are often treatable, however if they persist or worsen, consider the safety of complex tasks such as driving or traveling alone.
Daily Living:
Remove clutter or other tripping hazards to reduce the risk of falls while moving throughout the home.
Improve lighting throughout the home, especially in high fall risk areas such as entrances to the home, stairs, bathroom, and kitchen.
Increase the color contrast throughout the home for improved occupational performance.
For meal times try to use light dishes on a dark place mat or dark liquids in a lighter cup for better precision.
In the bathroom try to have products in various colored bottles (shampoo in a red bottle, conditioner in a green bottle, etc.) for easier identification.
Place brightly colored tape at the threshold of doors, stairs, showers, etc. to reduce fall risk.
Place brightly colored tape on harder to find items such as lightswitches or remotes throughout the home.
Change the contrast and font size on your smartphone for easier use, and try using the search bar for pulling up apps if possible, rather than visually scanning each page to save time.
Try setting up auditory or voice activated solutions if possible, like using alarms rather than visually checking clocks or timers, listening to books rather than reading, or having programs such as Siri/Alexa do things like read texts aloud or turn on the lights of the home.
Staying active:
Try creating art of any kind. The process of creating art relies on complex visuospatial and cognitive skills, and can help to improve visual function, as well as general motor function in people with Parkinson’s Disease.
Try other challenging activities for visual skills such as completing puzzles, mazes, word searches, and reading.
Incorporate eye exercises into your daily routine. These exercises will not only help your eye health, they can even lead to improved balance and reduce the risk of falls.
Depth perception exercise: try the “pencil push” by holding a pencil with the point up to the ceiling, slowly move the pencil closer to your face while maintaining focus on it.
Peripheral vision exercise: focus on a center point and without moving your head, try to identify objects as far to the sides of your field of vision as you can.
Tracking exercises: either with a partner or using a wall to rebound, try to keep a balloon off the floor by visually tracking, and tapping it back and forth.
Color contrast exercise: try using color vision deficiency tests as practice for contrast sensitivity.
Figure 1. Color Deficiency Test Example. Source: https://colormax.org/color-blind-test/
Take the test by clicking here https://colormax.org/color-blind-test/
References
American Parkinson Disease Association. (2019, March 28). Eye & Vision Issues | American Parkinson Disease Assoc. https://www.apdaparkinson.org/what-is-parkinsons/symptoms/eye-vision-issues/
Kanchian, V. (2023, July 13). Guide to vision Issues in Parkinson’s: Symptoms & Treatments. PCLA. https://pcla.org/guide-to-vision-issues-in-parkinsons-symptoms-treatments/
Weil, R. S., Schrag, A. E., Warren, J. D., Crutch, S. J., Lees, A. J., & Morris, H. R. (2016). Visual dysfunction in Parkinson's disease. Brain : a journal of neurology, 139(11), 2827–2843. https://doi.org/10.1093/brain/aww175
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