Our sensory perceptions help us navigate through the world. Changes to senses, such as vision, can sometimes progress alongside Parkinson’s disease (PD). In some cases, a reduced sense of smell can even precede a PD diagnosis by several years. Identifying and addressing vision changes early can foster continued independence and can also prevent injuries and falls.
This article is based on Sights, Sounds and Parkinson's, a Parkinson’s Foundation Expert Briefing webinar exploring PD and sensory changes, presented by Ali Hamedani, MD, MHS, Professor of Neurology, Divisions of Neuro-Ophthalmology and Movement Disorders, Perelman School of Medicine at University of Pennsylvania — a Parkinson’s Foundation Center of Excellence and PD GENEration enrollment site.
Parkinson’s and Sight
Sight guides many of our daily activities, including reading, texting and driving. In fact, about 40% of our brains are devoted to vision — making it our most dominant sense.
While vision changes are part of aging, Parkinson’s can also impact sight. The American Academy of Ophthalmology recommends a complete eye exam every year or two after 65. Your eye doctor might also refer you to a neuro-ophthalmologist — a neurologist or ophthalmologist with expertise in how neurologic issues impact vision.
While everyone experiences Parkinson’s differently, the disease can impact vision in many ways, most of which are treatable. Though exercise in general can improve many symptoms of Parkinson’s, eye muscles generally can’t be strengthened through exercise.
5 Visual Symptoms Common to People with PD
1. Dry eyes affect people with Parkinson’s due to decreased blinking, and certain PD medications such as amantadine. The condition can be uncomfortable, painful and deceptive.
Some might sense an actual feeling of dryness, while others experience blurry vision, increased glare or sensitivity to light. Soreness, stinging, itching or redness can accompany dry eyes. For some it can feel as if sand is in the eyes. Others may experience watery eyes from dryness.
Dry eyes can even be asymptomatic. Some people with Parkinson's learn from their ophthalmologist they have the condition. Even those without symptoms should take it seriously. Untreated, dry eyes can scar the outer layer of the eye. To treat dry eyes, try preservative-free, over-the-counter eyedrops or artificial tears. Avoid anything designed to reduce redness — this can irritate or worsen dry eyes.
Nighttime dry-eye drops are thicker than daytime drops, as our eyes tend to dry out during sleep. Use artificial tears from four to six times a day. If you take carbidopa/levodopa, try using artificial tears at the time you take your medication. If needed, your eye doctor can offer prescription eye drops or procedures to boost lubrication.
While good for everyone, taking part in an active lifestyle — moving and looking around, exercising and engaging with people — also boosts blinking. Be mindful of too much television or screen time, which can worsen dry eyes.
Blepharitis, eyelid inflammation due to oil and bacteria, can precede or accompany dry eyes. Use warm compresses to ease irritation. Soak a clean washcloth in warm water, then place it over your closed eyelids for 5 to 10 minutes to loosen oils and clean the area.
2. Double vision, seeing two of the same thing — something up to 30% of people who live with Parkinson’s experience — can occur due to:
- An eye problem such as dry eye, cataracts or the need for eyeglasses.
- Individually healthy eyes that point in slightly different directions.
3. Convergence insufficiency — double vision when focusing on nearby objects, such as reading a book — can emerge or worsen after deep brain stimulation (DBS).
A special type of eyeglass lens, called a prism, can help resolve double vision. Wearing an eye patch as needed can help, too.
Reading — a complex and demanding task — demands clear vision. Anything affecting vision, including dry eyes or double vision, impacts reading ability.
A person with Parkinson’s can benefit from having separate distance and near glasses, rather than bifocals or progressive lenses — which limit the amount of space someone is able to look through to read. People with PD have difficulty generating quick and accurate eye movements in small spaces.
4. Depth perception — understanding where things are in space — can be another common visual PD challenge. Each of our eyes only sees an image in two dimensions. Our brain combines those images to produce a three-dimensional map of the space around us.
Depth perception difficulty can happen if one eye is impaired, whether from a cataract, the need for glasses or something else. Double vision can also impede depth perception. Depth perception challenges can trigger freezing, a Parkinson’s phenomenon that feels as if your feet are temporarily stuck to the floor. This tends to happen in narrow spaces, such as doorways or hallways.
Depth perception issues are also among the Parkinson's-related visual symptoms that can affect driving. People with Parkinson's often must stop driving at some point, but usually not solely due to vision issues. Coordination challenges, delayed reaction time and cognition impairments can all contribute to the need to retire a driving license.
Impaired depth perception is not something that can be readily fixed with either medication or glasses. Management includes good lighting — essential for nighttime bathroom visits — and visual cues, such as a portable laser device that shines a line for you to step over.
5. Visual hallucinations, seeing things that aren’t there, is something about half of people who live with Parkinson’s will experience during their journey. These and other types of PD-related hallucinations can worsen with certain medications.
Research points to reduced visual function as a possible hallucination risk factor. There is a constant balance in the brain between external and internal visual stimulation. An imbalance between visual information coming from the outside world and information stored in the brain, such as images from previous memories or dreams, can drive hallucinations.
Hallucinations can include the illusion of a presence or movement in the peripheral vision, or the sense of a brief shadow or passing shape, such as an animal or child. Visual hallucinations can also be distressing. It is important to report even mild hallucinations to your Parkinson’s doctor, who might adjust PD medications or offer targeted treatment.
PD and Other Sensory Changes
Although rare, involuntary eye closure — or eyelid-opening apraxia — can also impact some people with PD. Wearing a headband around the forehead can help keep eyes open, as can wearing goggles. Your neurologist might also consider adjusting your medications. Blepharospasm — an involuntary squeezing and closing of the eyes — can be treated with regular botulinum toxin (Botox®) injections.
Though less studied than vision difficulties, some research suggests people who live with Parkinson’s can experience reduced hearing, compared to people without PD. This can include difficulty telling where sounds are coming from — such as the direction of an approaching car. Hearing aids or assistive listening devices can help.
PD can also impact the sense of smell. Taste and smell are linked. A diminished sense of smell might lead to a reduced appetite. Be sure to eat a nutritious, balanced diet — a key to maintaining good health with Parkinson’s.
Call the Parkinson’s Foundation Helpline at 1.800.4PD.INFO (1-800-473-4636) for expert care referrals and answers to all your Parkinson’s disease questions.