How Does Parkinson's Affect Vision?
We often read new articles about Parkinson’s disease (PD) that identify one of many non-motor complications of the disease. Upon first hearing of a Parkinson’s diagnosis you think about tremors, rigidity and difficulties with gait. Recently more information is available about non-motor issues like changes in mood and behavior, sensory problems like the loss of sense of smell, and difficulty hearing. Now more is recognized about vision complications.
Vision issues in Parkinson’s can range from dry eyes and blurry vision to difficulty controlling eye movements, the inability to open eyelids, and increasing likelihood of hallucinations. PD can cause eye or eyelid problems, as can side effects of medications used to treat the disease. Unrelated ocular conditions and progressing age can also lead to eye and eyelid issues.1
Sudden visual changes should be immediately reported to your doctor because, as with other PD symptoms, most related symptoms take time to develop. An illness, change or cessation in medication or other circumstances that come on quickly, can often be resolved just as quickly by seeking medical care.
Why does Parkinson’s affect the eyes?
Parkinson’s is characterized by a loss of dopamine producing cells in the substantia nigra portion of the brain. The reduction of dopamine can affect the visual cortex. So Parkinson’s can impair mobility of the eyes just like the limbs. There are several kinds of visual disturbances that may be experienced by people with Parkinson’s. Many who experience changes in vision or eye mechanics seek out a consultation from a neuro-opthalmologist, someone who specializes in visual problems associated with neurological disease.2
Changes in the structure of the eye related to PD are limited primarily to effects on the retina, which, like the substantia nigra is similarly affected by dopamine depletion. Color vision, particularly the ability to discern between shades, can be reduced due to the loss of dopaminergic receptors in the retina.3
The use of prescription eyeglasses can address some vision symptoms. Different kinds of corrective lenses can be used for reading and distance vision. Some who experience difficulty focusing their eyes can be fitted for glasses with prisms. Just like holding a glass up to the light can show you rainbow colors by bending the light, prisms added to lenses help to adjust the focal point on the retina. This can help reduce fatigue and double vision.2
Types of eye movements
There are three kinds of eye movements that can change with PD:
- Saccadic rapid eye movements direct us to gaze at a specific object or to read lines of print.
- Pursuit eye movements allow us to follow an object as it moves.
- Vergence eye movements allow us to move our eyes in different directions2
Changes to these eye movements due to Parkinson’s can also result in different kinds of visual difficulties. The inability to control eye movements can lead to involuntary blinking, double vision and other motor issues that can affect visual acuity.
Dry eyes can be treated with drops or ointments, warm wet compresses, but are not generally cured. The blink reflex can be impacted by PD. This manifests as either a slowing of the reflex, appearing as inappropriate staring, dry or burning eyes; and by reduced vision. Blepaharospasm and apraxia are two common eyelid motion issues. Blephararospasms are eyelid spasms that cannot be controlled, cause eyelids to squeeze, and can be relieved with Botox injections. Apraxia is a condition that makes it difficult to open eyes. There are specialized lid crutches and cosmetic tape that can be applied to hold the eyelids open.2
PD medications can affect your eyes as well as controlling motor symptoms associated with the condition. A complete history of the drugs, supplements and vitamins you taken is important in evaluating visual symptoms in people with PD. Specific medications, their dosages and the individual medication cycle may cause visual impairment. Therefore, improvement may also be made due to adjustments in medications.3
Visual hallucinations are generally associated with the psychological factors of PD. Generally attributable to cognitive defects, disease progression over time, and daytime sleepiness; it can also be exacerbated by medications.
People with PD may experience a variety of visual, motor and behavioral symptoms during the course of their disease and no two people are likely to experience them the same way. Visual changes can be mild, experienced as dry eyes and blurry vision, decreased ability to discern color, and slower pupil reactivity. Or they can be more significant affecting ocular movements, slower processing and an inability to control to operation of eye movements. Visual deterioration can impact quality of life by increasing risk of falls and a potential for developing visual hallucinations.
Fortunately, visual problems in PD can generally be treated. A visit to the doctor and ophthalmologist or neuro-opthalmologist can provide clinical insight. An examination can determine if there are physiological defects of the eye, or if medication side effects are the cause of visual disturbances. Changes in medication and prescription glasses or prisms may help resolve some or all visual changes, leading to more comfortable quality of life.
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