As people with Parkinson’s know all too well, the disease can cause many more symptoms than those that are noticeable from the outside. Some of the lesser recognised ones — even among doctors — involve the eyes and visual system. Parkinson’s can cause many symptoms, ranging from dry eyes to double vision. Not only can visual disturbances interfere with reading or driving, but they can also worsen walking or balance problems, and even contribute to hallucinations.
Vision problems can be due to Parkinson’s disease (PD), the medications used to treat it, or to unrelated conditions of the eye or eyelid.
Visual Disturbances Can Be Part of Parkinson’s Disease
Just as Parkinson’s can affect general mobility, it can impair movement of the eyes, which may result in difficulty keeping objects in focus or seeing things close up, as when reading. To treat these symptoms, doctors may prescribe corrective lenses and/or prisms (special lenses) and adjust Parkinson’s medications.
Parkinson’s may also dampen the ability to sense individual colours or make them appear duller. PD causes a loss of retinal cells in the eye that rely on dopamine to process and perceive colour.
Parkinson’s may also impact the eyelids. People with PD blink less frequently, which can lead to dryness, irritation or burning of the eyes. Sometimes it even causes blurred vision. Eye drops and ointments may help.
Some people with Parkinson’s have the opposite problem of excessive blinking which may lead to involuntary closure of the eyes, called blepharospasm. The treatment of choice for this problem is botulinum toxin injections into the eye muscles.
A few people experience a syndrome called eyelid apraxia that causes difficulty opening the eyelids. Special tape, glasses with wire loops or “crutches” can help hold the eyelids open.
Many people are familiar with dyskinesia — the abnormal, involuntary movements of the body that may occur with longer course of the disease and many years of levodopa usage. Few people are aware, though, that dyskinesia can also affect the eyes and cause blurred vision. If someone is experiencing dyskinesia in other parts of the body, this might be the culprit for visual disturbances. Medication adjustments may be the solution.
While dyskinesia typically happens in the “on” state — when Parkinson’s symptoms are otherwise well-controlled, some people experience worsening of vision as medication starts to wear off and Parkinson’s symptoms return. Medication adjustments would likely be beneficial in these situations as well.
Medications May Affect the Eyes
All prescriptions have potential side effects and some of these involve the visual system.
Anticholinergic medications, such as Artane (trihexyphenidyl) — which is used to treat tremor — can lead to dry eyes and blurred vision. Treatments include eye ointments or drops, or warm compresses. If symptoms are severe, it may be necessary to switch medications.
In more advanced PD, hallucinations (seeing things that aren’t there) and illusions (misinterpreting things that are there — thinking a tree is a person, for example) may occur. These visual symptoms can also be a side effect of some Parkinson’s medications. In general, they are more likely to happen in people who have ongoing problems with their vision (they need corrective lenses or have other conditions affecting the eyes, for instance).
Visual Problems Are Also a Common Part of Aging
As you get older, several diseases of the eyes can occur regardless of whether you have Parkinson’s disease. These include cataracts, macular degeneration and glaucoma.
A cataract is a clouding of the lens of the eye, which can cause blurred or double vision, colour fading or poor night vision. Surgery can correct this problem.
Macular degeneration is damage to the macula — a small part of the retina that maintains the centre field of vision. As this disease progresses, images in this area can appear dark, blurry or distorted. Limited treatments are available.
Glaucoma is an elevated pressure in the eye, which can damage the optic nerve and lead to vision loss. It is treated with eye drops or surgery.
Many Ways to Manage Vision Problems in Parkinson’s
When a visual symptom arises in the course of Parkinson’s disease, it’s important to rule out other conditions. Don’t assume it’s due to PD, especially if it comes on suddenly or fluctuates. People with Parkinson’s can certainly have other medical problems that can affect vision.
If Parkinson’s or the medications used to treat it are thought to be the reason for your visual symptoms, your neurologist can adjust your treatment regimen. If this doesn’t work (or even if it does), consultation with an eye doctor or a neuro-ophthalmologist — a doctor with training in both neurology and ophthalmology — may be beneficial. He or she can examine for and treat all of the conditions listed above.
If you’re experiencing changes in your sight, don’t automatically blame it on age or Parkinson’s. Raise the issue with your doctor, ask what could be causing your symptoms and determine what can be done to ease them. Together you can work to find a solution that will lessen your visual symptoms and improve your quality of life.
Source: The Michael J. Fox Foundation for Parkinson’s research