Parkinson’s Disease and Its Impact on Vision 

Parkinson’s disease (PD) is a chronic condition where a part of the brain deteriorates, causing severe difficulty with muscle control, balance, and the body’s movement over time. It can cause a broad range of other effects related to one’s senses, the ability to think, and mental health, such as depression and anxiety. The condition is caused when neurons in the brain responsible for producing dopamine die out or become defective. Dopamine is the chemical in the brain used to send messages to the brain that control movement.   

Prevalence of Parkinson’s 

According to Prevalence & Incidence | Parkinson’s Foundation, nearly one million people in the U.S. are living with Parkinson’s disease (PD). This number is expected to rise to 1.2 million by 2030. Parkinson’s is the second-most common neurodegenerative disease after Alzheimer’s disease. 

Nearly 90,000 people in the U.S. are diagnosed with PD each year. 

  • The incidence of Parkinson’s disease increases with age, but an estimated four percent of people with PD are diagnosed before age 50. 
  • Men are 1.5 times more likely to have Parkinson’s disease than women. 

A Study 

A 2022 Parkinson’s Foundation-backed study, “Incidence of Parkinson’s Disease in North America“, revealed that nearly 90,000 people are diagnosed with Parkinson’s disease in the U.S. each year. The rate represents a steep 50% increase from the estimated 60,000 diagnoses annually. The study found that: 

  • PD incidence estimates increase with age in the 65+ range. 
  • The primary risk factor for PD is age. 
  • PD incidence estimates are higher in men compared to women at all ages. 
  • The increase in the incidence of PD aligns with the growth of an aging population. 
  • PD incidence rates are higher in specific geographic regions: the “Rust Belt” (parts of the northwestern and midwestern U.S. previously regulated by industrial manufacturing), Southern California, Southeastern Texas, Central Pennsylvania, and Florida. 

This study is the most comprehensive assessment of Parkinson’s Disease incidence in North America. It is based on five epidemiological (the study of a disease and its impact) data sets to count the number of diagnoses in 2012. Prior PD incidence rates, based on smaller studies, were estimated to be in the 40,000 – 60,000 range per year. The new incidence rate is 1.5 times higher at nearly 90,000 cases annually. More information is available on the Parkinson’s Statistics webpage. 

What is Parkinson’s? 

Parkinson’s disease is a neurodegenerative disorder that predominately affects the dopamine-producing neurons in a specific area of the brain. The substantia nigra, a basal ganglia structure located in the midbrain, plays an important role in reward and movement. It also plays a part in the chemical signaling in the brain, affecting learning, mood, judgment and decision-making, and other high-level processes. 

Parkinson’s disease is a progressive disorder that affects the nervous system and the parts of the body controlled by nerves. Symptoms start slowly. The first symptom may be a barely noticeable tremor in just one hand. Tremors are common, but the disorder may also cause stiffness or slowing of movement. 

Stages of Parkinson’s 

In the early stages of Parkinson’s disease, your face may show little or no expression. Your arms may not swing when you walk. Your speech may become soft or slurred. Parkinson’s disease symptoms worsen as your condition progresses over time. 

The cause of Parkinson’s is not yet known. Scientists believe a combination of genetic and environmental factors is the cause. Research conducted by the Parkinson’s Foundation has led to breakthroughs in treatment and improved care that bring hope to the Parkinson’s community. The field of Parkinson’s research is ongoing and ever-evolving as we learn more about this disease. 

Diagnosis 

Scientists are exploring ways to identify biomarkers for PD that can lead to earlier diagnosis and more tailored treatments to slow down the disease process. Currently, all therapies used for PD can improve symptoms but do not slow or halt its progression. 

While Parkinson’s disease is not curable, it is treatable. Medications have the potential to improve the devastating symptoms of the disease.   

Symptoms 

Parkinson’s symptoms vary from person to person. Early symptoms may be mild and go unnoticed. Symptoms often begin on one side of the body and usually remain worse on that side, even after symptoms begin to affect the limbs on both sides. 

People with PD may experience: 

  • Tremor- Tremors typically occur when at rest. Tremors are rhythmic shaking and usually begin in a limb, often your hand or fingers. You may rub your thumb and forefinger back and forth. This is known as a pill-rolling tremor. Your hand may tremble when it is at rest. The shaking may decrease when you are performing tasks. 
  • Slowed movement, known as bradykinesia- Over time, Parkinson’s disease may slow your movement, making basic tasks difficult and time-consuming. Your steps may become shorter when you walk. It may be difficult to get out of a chair. You may drag or shuffle your feet as you try to walk. 
  • Rigid muscles- Muscle stiffness may occur in any part of your body. Stiff muscles can be painful and limit your range of motion. 
  • Impaired posture and balance- Your posture may become stooped. Or you may fall or have balance problems as a result of Parkinson’s disease. 
  • Loss of automatic movements- You may have a decreased ability to perform unconscious movements, including blinking, smiling, or swinging your arms when you walk. 
  • Speech changes- You may speak softly or quickly, slur, or hesitate before talking. Your speech may be more monotone rather than have the usual speech patterns. 
  • Writing changes- Writing may become difficult, and your writing may appear small. 

Motor symptoms of PD become evident later in the course of the disease after 60% to 80% of the substantia nigra neurons have already been lost or impaired. Lewy bodies are found in the substantia nigra neurons of people with PD. Lewy bodies are protein deposits that develop in nerve cells in the brain. The protein deposits affect brain regions that are involved in thinking, memory, and movement. People with PD or Lewy body dementia might experience some of the same symptoms, such as rigid muscles, slow movement, trouble walking, and tremors. 

In addition to movement-related symptoms, Parkinson’s symptoms may be unrelated to movement. People with PD are often more impacted by their non-motor symptoms than motor symptoms. Examples of non-motor symptoms include depression, anxiety, apathy, hallucinations, constipation, orthostatic hypotension, sleep disorders, loss of sense of smell, and a variety of cognitive impairments. 

Treatment 

The most common and effective treatment for Parkinson’s disease is levodopa, also referred to as l-DOPA. This is often combined with other medications to keep the body from processing it before it gets to the brain. Brain cells change it into dopamine, the chemical the brain uses to send signals that help you move your body. Combining medications helps avoid side effects of dopamine, such as nausea, vomiting, and low blood pressure when you first stand up. Over time, the way the body uses levodopa changes, so the drug can also lose effectiveness. Increasing the dosage can help for a while but also increases the severity of side effects. Increasing the dose can eventually become toxic.   

Treatment options vary and include medications, lifestyle adjustments, and surgery. While Parkinson’s itself is not fatal, disease complications can be serious. The Centers for Disease Control and Prevention (CDC) rated complications from PD as the 14th cause of death in the U.S. 

It is possible to have a good quality of life with PD. Working with physicians and following recommended therapies are essential in successfully treating symptoms using dopaminergic medications. People with PD need this medication because they have low levels or are missing dopamine in the brain, mainly due to impairment of neurons in the substantia nigra. 

People with Parkinson’s disease may have various symptoms related to their vision, such as trouble reading, double vision, and dry eyes. While these issues do not affect every person with PD, it is important to know what the different possible issues are and that there are a variety of ways to treat them. 

The most common symptoms of vision changes relating to PD include double vision, blurry vision, dry eye, and visual hallucinations. 

  • Double vision can often occur because the eye muscles have trouble working together, especially when seeing up close. Issues with eyes working together is called convergence insufficiency. Special prism glasses can often correct this. 
  • Dry eye due to decreased blinking is associated with PD and can cause blurry vision. Typically, a person blinks between 20 and 30 times per minute. In those with PD, deficient dopamine levels may reduce their blinking rate to 1–2 times per minute, leading to dry eyes. 
  • Blurry vision can also be caused by medication for PD, especially anticholinergics (such as trihexyphenidyl/Artane® or benzotropine/Cogentin®). 
  • Difficulty reading can occur because the eye movements necessary to follow the lines of a page are slowed and have trouble starting, similar to gait freezing in the legs caused by PD. Sometimes, it helps to try blinking to change eye position. Levodopa can often help.   
  • Trouble voluntarily opening the eyes, known as apraxia.  

Treatments include “lid crutches” or botulinum toxin injections.  

  • Visual hallucinations are non-motor symptoms that occur when a person sees things that are not there. Visual hallucinations affect approximately 75% of people with PD as the condition progresses. In those with PD, an imbalance between external visual information and internal visual stimulation within the brain can cause visual hallucinations. Certain PD medications can also affect a person’s visual perception. 

People with Parkinson’s can also experience eye movement, awareness, and color contrast problems. Some report that their vision loses sharpness as their disease progresses. Difficulties related to the eyes and vision often progress alongside other PD symptoms. 

Tips for Managing Vision Changes 

Taking part in an active lifestyle by moving and looking around, exercising, and engaging with people is important to eye health. It can boost blinking and minimize dryness.  

Watching too much television or screen time can worsen dry eyes. 

  • See your ophthalmologist regularly for an eye examination. 
  • Consider owning two pairs of glasses, one for distance and one for reading. This may be better than bifocals. If you have double vision, ask your ophthalmologist if prescribing prism glasses can help. 
  • Apply warm, moist compresses for eyelid irritation. 
  • Use artificial tears to moisten dry eyes. 
  • Consider adding a neuro-ophthalmologist to your medical care team. This specialist, either an ophthalmologist or a neurologist, has additional training in diagnosing and treating eye and vision problems associated with PD and other neurological diseases. 

Conclusion 

Parkinson’s disease is a prevalent condition and is more common among older adults. While not curable, many medications and surgery can be effective treatments. Many individuals with Parkinson’s can live years with the condition and can adapt with treatments that can help to address its symptoms.   

The Parkinson’s Foundation research has led to breakthroughs in treatment and improved care bringing hope to the Parkinson’s community. The field of Parkinson’s research is ongoing and continues to evolve as we learn more about this disease. 

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