Ocular and Visual Disorders in Parkinson’s Disease: Common but Frequently Overlooked
Journal of Parkinsonism & Related Disorders
Ekker, M.S., Janssen, S., Seppi, K., Poewe, W., de Vries, N.M., Theelen, T., Nonnekes, J. Bloem, B.R. (2017). Ocular and visual disorders in Parkinson’s disease: Common but frequently overlooked. Parkinsonism Relat Disor, 40, 1-10.
Most people are familiar with the hallmark symptoms of Parkinson’s disease (PD), which include motor abnormalities such as tremor, rigidity, slowed movement, and poor balance. In more recent years, we are learning more about the about the non-motor features of Parkinson’s, which include depression, anxiety, apathy, impulse control difficulties, problems with thinking, changes in speech, and visual hallucinations. Changes in vision for individuals with PD is less known and understood. Moreover, even physicians and researchers who frequently work with individuals who have PD are often underinformed about symptoms that effect the functioning of the eyes.
Timely identification of visual (also known as “ocular”) symptoms in PD is important for several reasons. Timely and effective treatment of visual symptoms is important because problems with vision have detrimental effects on peoples’ ability to walk, read, drive, socialize, and live independently. Impaired vision can also negatively impact one’s ability to benefit from common neuro-rehab techniques aimed at reducing troubling PD symptoms such as “freezing of gait.” Perhaps one of the most important implications for understanding visual functions in PD relates to predicting the course of or identifying risks related to PD. Visual impairment has been found to predict changes in cognition in individuals with PD, and individuals who suffer from visual hallucinations are most likely to require nursing home placement. Researchers are quickly catching on to the fact that identification and treatment of vision abnormalities in individuals with PD is essential to preserve independence and enhance quality of life.
The six most common (and disabling) eye and visual problems faced by individuals with PD are:
- Dry Eye Disease: More than 50% of individuals with PD suffer from dry eyes, and it most likely is a result of slower rate of blinking, which can dry out the eyes. Symptoms of dry eyes include burning sensation, frequent tearing, blurry vision, gritty or sandy sensation in the eyes, red eyes, or a feeling of pressure or pain behind the eyes. Right now, the most common treatment is artificial tears (or eye drops). Some research also indicates that an increase in intact of omega-3 and omega-6 (either by taking supplements or changes to one’s diet) can help. The most extreme treatment option is surgical, but there are often side effects.
- Oculomotor Disturbances and Diplopia: Oculomotor disturbance are fancy terms for difficulty moving the eyes smoothly and effectively (i.e., difficulty scanning left to right or looking up and down). Research on this is somewhat limited but it’s estimated that about 10-30% of individuals with PD suffer from these difficulties, with rates likely climbing higher as the disease progresses. It’s also worse in individuals who struggle with daytime fatigue. People most often notice these symptoms when reading. Treatment involves a type of physical therapy called “base-in prism and convergence exercises” as well as dopaminergic treatment (i.e., regular PD medication). Diplopia means double vision, and many individuals with PD experience this symptom.
- Glaucoma and Visual Field Loss: Glaucoma is an eye disorder that cause damage to the optic nerve that carries information from the eye to the brain. Many individuals are unaware that they have glaucoma until it has progressed to include more “central” or non-peripheral loss of vision. Research on prevalence rates of glaucoma in individuals with PD is scarce, even though some studies estimate that between 16-24% of individuals with PD experience glaucoma. Treatments include eye drops or surgical intervention.
- Color and Contrast Impairment: Contrast sensitivity can result in problems navigating situations when there is low light (like driving at night). Color discrimination is when you have a hard time seeing subtle differences in color. These problems are common in PD, but we don’t know how prevalent these symptoms are. Treatment is minimal, but some studies have shown that people see improvements with dopaminergic therapy, use of yellow filtering glasses (to eliminate glare). Selective absorption glasses (filer clips that attach onto regular glasses) may also be helpful. To be safe, most doctors will advise patients with these symptoms to avoid driving after dusk or before dawn.
- Visuospatial and visuo-perceptual impairments: Some individuals with PD struggle to accurately perceive (or see) things in space, mentally process 3D objects or solve visual problems. The most commonly difficulty in day-to-day activities involves challenges related to detecting human movement and having a hard time recognizing faces. People with these symptoms may also bump into doorways or freeze suddenly when walking.
- Visual Hallucinations: Visual hallucinations occur when individuals see or perceive visual stimuli that is not, in fact, there. Prevalence rates are not well understood, with estimates ranging from 4% to 83%. Typically, once visual hallucinations exist, they persist and progress unless adequately treated. Treatment involves medication (anticholinergics, NMDA antagonists and MAO-B inhibitors, and/or reduction of dopamine agonists and reduction of levodopa, if it can be tolerated). Sometimes people find it difficult to tolerate these medication changes because it can result in increased motor symptoms. If this is the case, doctors can prescribe other psychiatric medications to try and address the symptoms.
In summary, a multitude of visual symptoms and disorders among individuals with PD are more common than people may realize. It is important for people with Parkinson’s to report symptoms to their physician, as many of these symptoms are treatable and information about visual symptoms can provide valuable information about prognosis. Failure to identify and treat visual symptoms may lead to decreased independence and poorer quality of life.