By Daniel Gold, D.O.
Do you, or does a person you know who lives with Parkinson’s disease (PD), experience problems with vision? Maybe it is difficult to see in the rain, or maybe it’s that colors seem less vibrant. Perhaps the eyes feel drier than usual. We do not usually think of issues like these as part of Parkinson’s, which is known primarily as a movement disorder. However, the fact is that they can be a part of the disease, and can affect everyday activities like driving and reading. Fortunately, most vision symptoms of PD are fairly easy to diagnose — and easy to treat.
The Eye-Brain Connection in PD
How does a neurological disease like Parkinson’s affect vision? The front of the eye is only the beginning of the complex system that allows us to see. After light enters the front of the eye, images are focused onto the back — that is, the retina. From there, the optic nerve carries visual information to the brain. In PD, changes in the eyeball itself, as well as changes in its connections to the brain, can lead to vision issues. For a person with PD to maintain healthy vision, it is important to undergo an annual eye exam with an optometrist or ophthalmologist to catch issues early on.
Common Vision Issues in PD
Most people with PD have normal or near-normal vision. However, they may experience a variety of bothersome issues which, together, can impact visual function. Here are some of the common ones.
Central and Color Vision
As we age, our ability to perceive contrast diminishes, and this impairment can be more severe in people who have PD. Many people with PD may have trouble seeing fine details — for example, seeing signs when driving, or while reading or watching TV. These complaints can be present even for people whose vision tests are normal during a routine eye exam.
Examples of contrast vision impairment include blurring of the edges of objects such as stairs, which can lead to a missed step or a fall, or difficulty seeing clearly at night. In addition, a person with PD may find that colors seem less vibrant. It turns out that some cells in the retina rely on levodopa, the precursor to dopamine that gets depleted in PD. When this occurs, the results can include dullness of color vision and poor contrast vision.
Unfortunately, there is no good treatment for color vision issues. To address contrast vision impairment, first take care of any other eye health issues, and then ensure that the prescription for eyeglasses is correct. People with PD who experience balance problems should avoid using progressive, bifocal and trifocal lenses. People with poor balance rely heavily on vision and tend to look down while walking. If they are wearing progressives or bi/trifocals, and use the reading (bottom) portion of their glasses to follow their feet, the visual correction at that distance will be incorrect. This can lead to disorientation and aggravate balance issues, leading to falls.
In daily life, when we need to keep our eyes focused on an object as it moves closer to us, we use a process known as convergence. It is common for people with PD to have trouble doing so because of “convergence insufficiency.” They may experience double vision, headaches, eyestrain or blurred vision. While reading, they may lose their place, feel tired, or find that words appear to move on the page. Or they may need to constantly adjust the distance of reading material from the eyes.
A neurologist, ophthalmologist or neuro-ophthalmologist can diagnose convergence insufficiency and other eye movement disorders, and prescribe a therapy. One such therapy consists of home exercises known as “pencil push-ups” — holding a pencil at arm’s length and bringing it to the nose, while trying to keep the tip in focus.
A quick fix for convergence issues experienced with reading is to cover one eye, or to put Scotch tape over one lens of reading glasses, so only one eye is used at a time. Another option involves the use of prisms placed in reading glasses (not distance glasses).
People with PD may receive a recommendation for vision therapy for ocular motor dysfunction. While evidence supports its efficacy for convergence insufficiency, there is no evidence it helps other eye issues. It can be expensive and is sometimes not covered by insurance; so be wary of what is being treated and covered.
Other common eye movement abnormalities in PD include impairments in processes known as saccades and smooth pursuit. Saccades are the quick eye movements a person makes, for example, to switch focus from one bird in the sky to another. In PD, saccades tend to undershoot the intended target. Smooth pursuit refers to slow eye movements involved in tracking objects, for example, following a bird as it flies across the sky, and in PD it may be more choppy than smooth. There are no good treatments for these issues, but they are usually very subtle.
Blinking and Dry Eye
Keeping the front of the eye moist is essential for good vision. Tears help the eye to see clearly, stay protected and move freely. Blinking helps squeeze out tears and distribute them in a moist layer on the eye.
With PD, people tend to produce fewer tears and blink less often. Some of the medications that are used to treat PD — for example, trihexyphenidyl (Artane®) — can contribute to dry eye. The problem may be exacerbated further by health issues, such as menopause or autoimmune disease. Other culprits include contact lenses, effects of eye surgeries and allergies. The result is that people with PD often have symptoms of irritation on the surface of the eye — dry eyes, a gritty or sandy feeling, burning, redness or crusting on the lashes.
These problems can be diagnosed by an ophthalmologist or optometrist. The first line of treatment is to use artificial tears (eye drops — preferably, preservative free) three or four times a day and more in addition as needed (e.g., while reading or watching television). If the problem is serious, the eye care professional may advise a prescription medication. For inflamed eyelids known as blepharitis, your doctor may recommend using hot compresses or lid scrubs (a liquid or pre-packaged pad that you place on the eye) to ease discomfort and keep the eye clear.
Less Common Vision Changes in PD
Some people with PD experience visual hallucinations as part of the disease. Usually hallucinations are not threatening; for example, a person might see a cat out of the corner of the eye. They occur more often in people with PD who experience daytime sleepiness, insomnia or cognitive difficulties, and among those whose PD is advanced. Almost all PD medications are able to produce or exacerbate hallucinations, although amantadine, pramipexole (Mirapex®), rotigotine (Neupro®) and ropinirole (Requip®) are the biggest culprits. People with mild hallucinations can often be helped with reassurance. If hallucinations are moderate to severe, medications should be evaluated and people with PD and their doctors can consider adding a medication to ease hallucinations.
Lastly, there is literature to suggest that people with PD may be at higher risk for certain non-neurologic eye diseases — a type of cataract called “posterior subcapsular cataract,” and primary open-angle glaucoma. An ophthalmologist or optometrist can detect these conditions.
Keeping the Vision Clear
What can a person with PD do to maintain good vision and ease the symptoms discussed above? The most important thing is to have an annual eye exam and follow any tips that are suggested by the doctor. This means that symptoms will be addressed early on to ensure the best quality of life. Good vision is essential to doing the things we want and need to do and luckily, most vision difficulties in PD can be easily diagnosed and treated.
Daniel Gold, D.O., is Assistant Professor of Neurology, Ophthalmology, Neurosurgery and Otolaryngology at Johns Hopkins University School of Medicine. He presented this topic as a PD ExpertBriefing, which is available online at www.pdf.org/parkinsononline.
Vision Care Professionals
An ophthalmologist or optometrist can diagnose and treat most vision difficulties that affect people with PD, and refer you to a neuro-ophthalmologist if further evaluation is needed.
- Optician: Not a doctor; makes glasses.
- Optometrist (O.D.): four years of optometry school after college; examines eyes, does vision tests, prescribes glasses and certain medications.
- Ophthalmologist (M.D. or D.O.): a doctor with four years of medical school, plus four additional years of ophthalmology training; diagnoses and treats eye diseases, prescribes and fits glasses.
- Neuro-ophthalmologist (M.D. or D.O.): a neurologist or ophthalmologist (training in either neurology or ophthalmology and then fellowship training in neuro-ophthalmology) who specializes in diseases that affect the visual pathways connecting the eyes to the brain, disorders of the eye muscles or nerves that can cause double vision or other symptoms, eyelid issues, jumping vision or nystagmus, pupillary abnormalities, among others.