According to the Mayo Clinic, Parkinson’s Disease (PD) “is a progressive nervous system disorder that affects movement. Symptoms start gradually, sometimes starting with a barely noticeable tremor in just one hand. Tremors are common, but the disorder also commonly causes stiffness or slowing of movement.” There many other prevalent symptoms and complications of Parkinson’s and the eyes are no exception.
Diplopia (Double Vision)
Diplopia is the medical term given to double vision. Unfortunately, it can be a common occurrence in patients with Parkinson's Disease. It may occur in up to 30% of PD patients. The exact mechanism for the cause of the double vision in not fully understood. The double vision may occur in straight-ahead gaze or in a particular direction of gaze (i.e. looking up). Another very common source of double vision in PD is “convergence insufficiency,” which is when the eyes are unable to converge normally for up close visual activities like reading. This would produce double vision when only reading.
Double vision may be helped with PD medications if the person is not actively being treated. Interestingly, some PD medications themselves may cause double vision. If the double vision is consistent, the optometrist may be able to prescribe prism in the patients glasses to help compensate for the misalignment causing the double vision. If the double vision is due to convergence insufficiency, a separate pair of reading glasses with prism compensation may be best.
This is a highly prevalent finding in Parkinson’s patients, affecting 50-60% of patients. Many PD patients have a “stare” type expression which results in a very decreased “blink rate.” Normally, we should blink involuntarily about 12-14 times per minute. That blink rate in PD patients may only be 3-5 times per minute. Less blinking means less tears secreted onto the eyes and more evaporation of the existing moisture. Besides causing burning, redness, itching, and discomfort, dry eyes can also cause blurry or fluctuating vision.
There are many treatments for dry eyes available to the optometrist. These range from recommending the appropriate OTC artificial tear drop to tear saver plugs inserted into drainage ducts to prescription eye drops. The exact treatments are determined by the severity of the condition, damage to the ocular surface, and effects on vision and patient quality of life.
This is when the muscles of the eyelid contract and blink subconsciously and uncontrollably. A PD patient with blepharospasms looks like they are constantly blinking, sometimes at a rapid rate. While this doesn’t cause damage to the eye, it can be a frustrating symptom to experience. Often, blepharospasms interrupt simple vision tasks like watching television, reading a book or a menu, and undergoing important eye exam testing.
The mainstay for treatment of blepharospasm in PD is botox injections. These can be administered by a neuro-ophthalmologist or oculoplastics specialist in an office or clinic setting. Because this is a medically necessary situation, insurances typically will cover botox for the treatment of blepharospasm. A single treatment may last for 3-4 months and need to be repeated once symptoms present again.
This may occur in as many as 1 out of every 5 PD patients, although it may not always be reported by patients to their caretakers or health care providers. Non-threatening hallucinations, such small shapes, animals, shadows, loved-ones are more common than threatening hallucinations. They may be the result of the disease process itself or Parkinson’s medications. They are more common in more advanced aged PD patients, as well as those who may have a dementia component. It’s important to ask about visual hallucinations specifically to encourage PD patients to share their experiences. When present, adjustments to medications may be warranted or can improve symptoms.
While these are the most commonly noted eye-related issues in Parkinson’s, this by no means the only potential complications. PD is a complicated disease, requiring potent medical treatments. This makes for the likelihood of these and/or other eye symptoms very likely. Other potential complications include nystagmus, visual-perceptual issues, decreased color perception, and optic nerve disease.
No matter the stage of disease, the optometrist can serve as an integral team member in the care of Parkinson’s patients to identify complications and improve quality of life. Regular trips to the optometrist, along with an open discussion about symptoms, can help over the long term with this challenging and complex disease.
Dr Russell Beach, O.D.