People with Parkinson’s disease (PD) may experience a change in vision as the condition progresses. They may experience dry eyes, double vision, and eye movement problems.
This article provides an overview of PD and its associated vision changes. It also covers the symptoms, causes, treatment, and management of PD-related vision changes.
Research from 2016 indicates that about
Without early diagnosis and prompt treatment, vision changes can affect someone’s ability to carry out daily functions, negatively affecting the quality of life of those with PD.
Double vision, or diplopia, occurs when a person sees two images of a single object. This can affect about 10–30% of people with PD.
A person with PD
- Monocular diplopia: Someone with monocular diplopia will have double vision in one eye, meaning they will experience blurred vision.
- Binocular diplopia: People with binocular diplopia have double vision in both eyes.
- Selective diplopia: This is a rare form of visual hallucination in people with PD.
Double vision, especially monocular diplopia, may also develop due to other eye conditions, such as dry eyes and cataracts.
A person can get prism glasses to help with binocular diplopia.
These lenses help align the two images so that they become one. They bend the light before it travels through the eye and redirect it to where it needs to go on the retina.
A 2019 article states that about
Typically, a person blinks between 20 and 30 times per minute. In those with PD, deficient dopamine levels may reduce their blinking rate to 1–2 times per minute, leading to dry eyes.
PD medications can also affect a person’s blinking rate.
According to the Parkinson’s Foundation (PF), dry eyes can cause:
- blurred vision
- sensitivity to light
- watery eyes due to excessive blinking
Dry eyes can also result in a condition called blepharitis. This is when the edges of the eyelid become swollen and itchy.
In some cases, dry eyes may not cause any symptoms. Some people with PD learn they have the condition after speaking with an ophthalmologist.
If someone takes levodopa or carbidopa for managing PD, they may wish to use them at the same time.
If OTC eye drops are not enough, an optometrist may recommend prescription eye drops.
If blepharitis develops, a person can use warm, moist compresses, lid scrubs, and medicated ointments.
People with PD may notice that their vision is blurry. This can be due to the medications they are taking or as a symptom of other vision changes they might be experiencing.
Blurry vision can develop due to:
- eye movement problems
- dry eyes
- PD medications called anticholinergics, including trihexyphenidyl (Artane) or benzotropine (Cogentin)
If the anticholinergics are the cause, a person’s blurry vision may resolve as the body gets used to the medications.
Alternatively, a person may require reading glasses. If they already have glasses, they should speak with an optometrist to ensure their lens prescription is correct.
The American Parkinson Disease Association states that there are three main types of eye movements:
- Pursuit eye movements: Let the eyes travel together to follow a moving object in the vertical or horizontal direction.
- Saccadic eye movements: Refer to the rapid eye movements that let the eyes jump quickly to another object.
- Vergence eye movements: Refer to when an object is either coming toward or away from a person.
Those with PD may have difficulty with saccadic and vergence eye movements. This can affect a person’s ability to read.
Those who are having trouble reading should contact an optometrist. They may be able to adjust a person’s lens prescription.
If the amendments to the lens prescription do not help, a person may require a referral to a neuro-ophthalmologist.
People may receive a prescription for two sets of glasses — one to help see things in the distance and one to help see things close up. Prism glasses may also be an option.
Those with PD may have difficulty judging the space around them.
The American Academy of Opthalmology defines depth perception as the ability to see an object in three dimensions, including length, depth, and width, and to judge how far the object is.
According to a
Neuroimaging studies have shown that people with untreated PD and impaired depth perception have reduced gray matter volume in the parts of the brain relating to vision.
The PF notes that medications or glasses are unlikely to help with eye movement problems. However, adequate lighting and visual cues, such as a portable laser device, may be beneficial.
Color discrimination is the ability to differentiate between different shades of color, while contrast sensitivity is the ability to distinguish an object from its background.
Common symptoms include low vision when driving in the dark or decreased attention span when reading texts on a colored background.
This may be due to a depletion in dopamine levels in the retina of the eyes.
Parkinson’s UK notes that medications for PD may help improve a person’s color vision.
Visual hallucinations occur when a person sees things that are not there.
A 2020 study suggests that visual hallucinations affect
In those with PD, an imbalance between external visual information and internal visual stimulation within the brain can cause visual hallucinations.
Certain PD medications can also affect a person’s visual perception.
If this does not work, they may prescribe cholinesterase inhibitors or antipsychotics, such as pimavanserin or clozapine.
Those with PD may experience blepharospasm, when a person blinks excessively.
They may also develop ocular apraxia. This refers to when a person cannot voluntarily open their eyes. It often happens when they are speaking. In some cases, the eyelids may completely close.
An ophthalmologist and neuro-ophthalmologist may recommend botox injections every 3–4 months to treat blepharospasm.
Botox injections can also help treat ocular apraxia in some cases. If the apraxia is mild, rubbing the eyes can help.
Alternatively, a person may benefit from lid crutches. These are tools that attach to a person’s glasses that help support the eyelids.
Vision changes in PD may occur due to the following.
Low dopamine levels
Research suggests that people with PD lose
Low dopamine levels can affect visual signaling, refractive eye growth, color vision, and contrast sensitivity, causing vision problems.
People with PD may experience vision problems as a side-effect of their medications.
For example, anticholinergics, such as trihexyphenidyl and benzatropine, may reduce the ability of the eyes to focus on near objects, causing blurry vision.
If a person with PD notices that their vision is changing, they should contact a doctor. They may be able to refer them to speak with the following medical professionals:
- Optometrists: These healthcare professionals examine the eyes and provide advice. They can also prescribe glasses.
- Ophthalmologists: These can examine, diagnose, and treat conditions that affect the eye.
- Orthoptists: These healthcare professionals can diagnose and treat visual conditions and atypical eye movements.
- Neuro-opthalmologist: These medical professionals can diagnose and treat vision conditions that result from a neurological condition.
If a person has PD, they should visit an optometrist for an eye test every year, even if they are not experiencing vision problems.
PD can affect a person’s vision. This may be due to low dopamine levels or side effects of certain PD medications.
Vision changes can include:
- double vision
- dry eyes
- blurred vision
- eye movement problems
- spacial awareness
- color vision changes
- visual hallucinations
- blinking abnormalities
The treatment of vision changes relating to PD will depend on the cause. The doctor will assess a person’s symptoms and recommend the best treatment.