Experts estimate that two-thirds of stroke survivors face challenges with their vision. Given that approximately 50-60% of our brain is dedicated to visual processing, this is not surprising. However, the impact of a stroke on vision can vary greatly, making individualized solutions for each person necessary.
Visual Field Loss
When a stroke occurs on one side of the brain, it can result in loss of vision on the opposite side of the visual field, known as hemianopia. Patients with hemianopia may mistakenly believe that only one eye is affected, but typically it is one side of the visual field in both eyes that experiences the loss. Some patients may not even be aware of the missing area of vision until they view themselves in the mirror and can only see one side of their face.
Less commonly, patients with visual field loss may experience visual hallucinations on the affected side, a condition called Charles Bonnet syndrome. It is important to note that these hallucinations are not a result of mental health disorders and most of them fade over time.
The severity and location of the stroke determine the extent to which vision may improve and some patients may make a complete recovery.
Prism glasses can be used to draw attention to the missing areas of the visual field, expanding visual awareness and widening the field of vision. By creating an image of the side of the visual field loss and reflecting it to the stronger side, prism glasses help compensate for the loss.
In places like Kelowna, specialized centers such as Okanagan Vision Therapy offer individualized vision therapy for stroke patients, assisting them in overcoming stroke side effects related to vision. Their tailored approaches help individuals navigate and adapt to their new visual challenges.
Visual Inattention and Hemispatial Visual Neglect
The most common visual processing problem after a stroke is inattention or neglect, where patients become unaware of visual information on one side of their body. This information is not actually lost; it is simply not attended to by the observer. Visual neglect typically occurs after a stroke on the right side of the brain, affecting the left side of visual space.
Visual inattention can make it difficult to make movements towards objects in the environment and can pose challenges while reading, particularly with horizontal eye movements. Visual field loss and hemispatial neglect can occur together, which informs the management approaches.
Management strategies for visual neglect often involve using prism glasses to draw attention to the affected field of vision, as well as functional tools like reading rulers and guiding lines along the sides of text. During recovery, touch or hearing can be used to enhance awareness of the neglected side.
Eye Tracking & Teaming Problems
As a result of a stroke, patients may present with challenges tracking objects or following movement with their eyes – making both driving and reading difficult. Additionally, patients may have struggles moving their two eyes together, resulting in symptoms of blurred or even doubled vision.
If our eyes are not moving together as a team, it will also impact depth perception – resulting in poor judgment of depth while navigating busier visual environments or varied terrain. In certain cases, a stroke may result in something known as nystagmus, where the eyes are always moving or “wobbling.” As you might expect, this constant instability of the eyes can lead to constant instability of the world.
Fortunately, many of the difficulties tracking and teaming of the eyes can be greatly reduced via therapeutic prism glasses and appropriate Vision Therapy. Clinics specializing in vision therapy, like Okanagan Vision Therapy in Kelowna, can provide guidance and targeted exercises to help address these issues.
For many who have sustained a stroke, weakness or loss of sensation on one side of the body will occur. In addition, one may struggle to lift their toes quickly enough to stop them from catching on the ground – a condition known as “drop foot.”
Intense focus is now required to make movements – forcing the body to automatically rely heavily upon vision to compensate for the lack of feeling or control. This concentration can be extremely tiring, making navigation of busy or noisy scenes challenging. It can be difficult to maintain balance and plan how to move if you are unsure of your own position in relation to the space around you.
Along with the impact on body movement, a stroke that occurs in the cerebellum or brainstem may also result in a condition called vertigo, where the world is constantly perceived as rotating.
As with problems of eye movement, an appropriate glasses prescription can make all the difference in the world for improving the affected depth perception and navigational skills.
Ocular Dryness and Light Sensitivity
Patients who have sustained a stroke may also suffer from dry eyes, due to a weakness in the muscles around the face and eyelids. Light sensitivity is also quite common.
Lubricating eye drops to manage ocular dryness, as well as appropriate tints in glasses will often make a world of difference for reducing these rather uncomfortable symptoms.
Following a stroke, some or all of the above visual sequelae may occur. With varying presentations, solutions must be individualized and tailored to address the needs and goals of every unique patient. One solution does not fit all, but it can be comforting to know that many hopeful strategies and solutions are available to those in need, especially when facilitated by reputable clinics like Okanagan Vision Therapy in Kelowna.
Until next month,
Paul Rollett, OD, FCOVD.