Parkinson’s disease is a chronic, progressive neurological disorder caused by death of Dopaminergic neurons in area of brain known as Substantia nigra, responsible for production of dopamine. This depletes the level of dopamine in areas of visual cortex and some cells of retina as well which may lead to problems such as blurred vision, dry eyes, double vision and sometimes visual hallucinations also.
The most common eye problems and vision difficulties found in patients with Parkinson’s disease are:
Visual motor disturbances
- Blurred vision: Difficulty in movement of eyeballs can impair the ability to keep track of objects travelling towards or away from the person and causes ‘’Blurred vision’’. Blurred vision can also occur as a result of side effects of medication (Anticholinergics).
- Double vision.
- Dry eyes: Normally an individual blinks about 16-18times/minute. But in PD the blink reflex may decreases up to 1-2 blinks/minute. This can dry the ocular surface and may lessen the production of protective tear film which can lead to ‘’Dry eyes’’. Because of reduced blink reflex people with PD often have a blank stare on their face.
- Apraxia: It is an inability to open eyes voluntarily which can be treated with lid crutches or lid tape that can help to hold the eyelids open.
- Patients with PD can often complain of trouble reading because of blurred/double vision.
- Blepharospasm and Blepharitis: Blepharospasm is spasm in eyelid which may lead to excessive blinking. Blepharitis is inflammation of eyelids. Both can worsen the symptoms of dry eyes.
- Excessive watering and tired eyes are also observed.
- Dysfunction of Dopaminergic receptors in retina (responsible for processing and perception of colour) may lead to decreased or loss of contrast of sensitivity in some people.
- Altered colour vision is observed. Sometimes colour blindness to yellow- blue colour can also be noticed.
- Spatio-Visual judgement is impaired which leads to difficulty in judging distance or space around or between objects which may make walking more difficult.
- Visual hallucinations: These are more common in chronic severe PD patients who can often complain of flickering lights, objects, people or animals
Vision difficulties due to Medication:
The commonly known effects of Parkinson’s disease is ‘’Dyskinesia’’ that is abnormal involuntary movements of body which sometimes can occur because of medication as well, if used for many years and may become a cause of blurred vision and visual hallucinations. In such situation, medication adjustment can help relieve or reduce the severity of symptoms.
Age related eye problems in PD:
Some visual problems can occur as a part of aging, irrespective of PD or not. These include:
- Glaucoma: It is elevated pressure in eye, which may lead to loss of vision. Glaucoma in PD patients can occur as a result of side effect of Anticholinergic medications and L-Dopa.
- Cataract: It is clouding of lens of eye leading to blurred or double vision. Laser eye surgery is proved to be effective.
- Macular degeneration: Macular degeneration in retina can severely affect the vision.
It is very important to reach the root cause of the vision disturbances. Sometimes people with PD can have other medical conditions which may be responsible for vision difficulties and it is not always PD that is causing vision problems.
- The first and foremost step in the management is the accurate and thorough eye and vision examination and correction of refractory errors (if any).
- It is very important to be aware of medication’s dosage, effects and side effects as sometimes they can affect vision and may exacerbate hallucinations.
- It is advisable to have two pair of glasses one for distance and other for reading in preference to bifocal lens. Sometimes prism glasses are also prescribed.
- Discomfort due to dry eyes can be managed with the use of artificial tears.
- People with Blepharospasm can benefit from injection of Botox in eyelids.
- Warm moist compresses or ointment can be helpful in eyelid irritation.
- Most importantly to reduce the chance of fall it is crucial to have good lighting source and good visual contrast between things to improve visual perception of patient.