Parkinson’s disease is a disorder of the nervous system that affects movement. It occurs due to the degeneration of the dopamine-production in the brain, particularly in the substancia nigra region.
Why Parkinson’s disease occurs exactly is not known but it is believed to occur from genetic changes and exposure to environmental factors such as toxins.(1)
Dopamine is a neurotransmitter that plays a critical role in regulating movement. When dopamine-producing neurons die, it can lead to movement-related symptoms. The main symptoms of Parkinson’s disease include tremors, stiffness, slowness in movement, and difficulty with balance and coordination. These symptoms affect a person’s ability to perform daily activities, walking, dressing, and eating.
Parkinson’s disease also affects the areas of the nervous system including the autonomic nervous system controlling autonomic functions like digestion, blood pressure, and heart rate. This can lead to constipation, urinary problem, and difficulty regulating blood pressure. People with Parkinson’s disease may also experience changes in vision. They may experience dry eyes, double vision, and problems with eye movement.
It can also lead to non-motor symptoms such as depression, anxiety, sleep disturbances, and cognitive changes.
Importance of Understanding Vision Problems in Parkinson’s Disease
Parkinson’s disease affects vision and may affect a person’s ability to perform daily activities and thereby impacting the quality of life. Research done in 2016 showed that about 78% of people with Parkinson’s disease have at least one vision symptom.(2)
Many people with Parkinson’s disease experience vision problems such as difficulty with depth perception, contrast sensitivity, and visual processing speed.
Problems with vision may also affect a person’s ability to drive, read, watch television, and perform daily activities. Difficulty with depth perception makes it difficult to navigate stairs or uneven surfaces and may also cause contrast sensitivity making it hard to see low light conditions.
Vision problems can also lead to falls and accidents that can be dangerous for older adults with Parkinson’s disease.
An understanding of how Parkinson’s disease affects vision can be helpful to healthcare professionals in providing appropriate treatment and help in managing symptoms. This can be helpful in reducing the risk of accidents and injuries.
Causes of Visual Symptoms in Parkinson’s Disease
The visual symptoms of Parkinson’s disease may occur due to the degeneration of the dopamine-producing neurons in the brain. Dopamine has a critical role in the visual processing centers of the brain.
Degeneration of dopamine-producing neurons may lead to visual symptoms including difficulty with visual processing, reduced contrast sensitivity, impaired depth perception, eye movement problems, and hallucinations. Research shows that people with Parkinson’s disease lose 60-80% of dopamine-producing cells in the substantia nigra.(3)
Parkinson’s disease also affects the structure of the eye including the lens and the retina which may contribute to visual symptoms. Changes in the lens of the eye may lead to blurred vision and retinal changes may lead to visual acuity and contrast sensitivity.
Also, medications used in the treatment of Parkinson’s disease such as dopamine agonists may also contribute to visual symptoms. These may contribute to visual symptoms including visual hallucination, particularly in older adults.(4)
Not all vision symptoms in Parkinson’s disease are caused due to the disease. However, other age-related factors or co-existing eye conditions may also contribute to visual symptoms.
Vision Symptoms in Parkinson’s Disease
In Parkinson’s disease, vision symptoms are very common. These may include:
Impaired Depth Perception and Spatial Awareness
Parkinson’s makes it difficult for a person to perceive distances accurately. This may lead to difficulty in judging distances, navigating stairs, and other activities requiring accurate depth perception.
A person with Parkinson’s disease may have difficulty judging the space around them.
According to the American Academy of Ophthalmologists, depth perception is an ability of an individual to see an object in three dimensions which include length, depth, and width.(8)
A study shows depth perception issues may be due to changes in vision processing due to Parkinson’s disease.(9)
Problems With Eye Movement
Parkinson’s disease may also affect the ability to control eye movements, which may lead to problems with tracking moving objects or shifting focus between the objects present far or near.
A person with Parkinson’s disease may also experience blepharospasm, a condition in which a person blinks excessively.
Sometimes apraxia may develop, in which the person is not able to open the eyes. This mostly happens when the person is speaking.
There can be changes in the lens and reduced tear production in Parkinson’s disease. This may lead to blurred vision.
Reduced Color and Contrast Sensitivity
In Parkinson’s disease, the ability to distinguish between light and dark areas is affected. This makes it difficult to see objects in low-light conditions. 18-50% of people with Parkinson’s disease have color and contrast vision.(6) There may be low vision while driving during the day and decreased attention span while reading text on a colored background.
This may be due to the depletion of the levels of dopamine in the retina.
Difficulty in Visual Processing
In Parkinson’s disease, the speed with which the brain processes visual information is affected. This results in slower reaction time and difficulty in tasks requiring quick responses.
Some people with Parkinson’s disease may experience visual hallucinations, where they see things that are not there. A study suggests that 75% of people with Parkinson’s disease have visual hallucinations.(5) There may be an imbalance in the external and internal visual information that may be the cause of hallucinations in those with Parkinson’s disease.
Treatment and Management of Visual Symptoms in Parkinson’s Disease
Visual symptoms of Parkinson’s disease can severely impact the quality of life of a person. The treatment options for them include the following.
The medication to treat Parkinson’s disease includes levodopa. It may include the treatment of visual symptoms. Dopamine agonists can also be helpful in improving visual perception.
If medications are the cause of the visual symptoms, the doctor may try to taper down the medication.
For the treatment of blepharospasm, botox injections may also be given.
Magnifiers, bright lights, and contrast-enhancing filters can benefit people with Parkinson’s disease. These can be helpful in improving visual acuity, contrast sensitivity, and color perception.
An occupational therapist can provide training in scanning and compensation techniques, thereby helping with visual deficits.
Changes can be made in lightening, color contrast, and texture to make it easy to see objects and navigate the environment.
Deep Brain Stimulation
This is a surgical procedure that can help in improving the motor symptoms of Parkinson’s disease. Studies show that it can help in improving individual perception and color vision in people with Parkinson’s disease.(10)
The visual symptoms vary from person to person and also do the treatment options. It is therefore important to consult a healthcare professional for the most appropriate treatment and management option.
Parkinson’s disease affects vision reducing contrast sensitivity, eye movement problems, impaired visual processing, visual hallucinations, and dry eyes. It is important to discuss visual symptoms with the healthcare professional and get detected at the earliest due to the following reasons:
- Early detection can improve the chances of treatment for the condition
- Proper management of symptoms can help in improving the quality of life
- Doctors can provide strategies to mitigate the risks associated with impaired depth perception and ensure safety.
- It can help in the management of symptoms and finding an appropriate treatment
Future Treatments and Management Options For Visual Symptoms In Parkinson’s Disease
Research is going on to develop new treatment and management options for Parkinson’s disease. The potential areas include:
- There is no medication yet that is specifically approved for Parkinson’s disease. Research is still being done to find a medication that may target neurotransmitters that involve visual processing.
- Gene therapy, a type of therapy in which a person’s genes are corrected to treat a disease. It is still in its early stages for Parkinson’s disease as research is exploring the potential for it to target visual symptoms.(7)
- Virtual reality, a technology that is being researched as a potential tool for improving visual symptoms in Parkinson’s disease. It can be helpful in stimulating real-world environments and providing training exercises in a controlled setting
- Rehabilitation program is another option that is being explored. People are developing an interest in rehabilitation programs for visual symptoms. These may include visual training exercises that aim to improve visual processing and eye movement.
- Deep brain stimulation, a surgical treatment that may involve implanting electrodes in specific areas to regulate abnormal neural activity.
Currently, there is no cure for Parkinson’s disease and research is going on to develop new treatment and management options. With continued research, there is hope that these approaches will help in improving the lives of people living with Parkinson’s disease.
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