With an estimated 65 percent of individuals experiencing some form of visual impairment following stroke, it's practical for survivors to develop an understanding of vision-related stroke terminology. For those following the Stroke Lingo blog series, our fourth installment explores words related to the visual system. Read along to get a glimpse at a variety of terms describing how a stroke can affect our ability to detect and interpret visual information.
Types of Post-Stroke Vision Changes
The visual field is the entire area the eye can see when in a fixed position.
Anopsia refers to the inability to see part or all of the visual field. This condition is also known as a visual field cut. There are multiple types of visual field cuts that can occur after stroke including:
Hemianopsia: Loss of one half of the visual field of each eye
Quadrantanopsia: Loss of one quarter of the visual field of each eye.
A visual field cut occurs after damage to the optic nerve fibers that relay signals from the eyes to the brain's main visual processing center, the occipital lobe. Depending on where this pathway is damaged, vision loss may result on the same side or opposite sides of each eye.
Those with a visual field cut are at risk of missing visual details in their blind spot. For example, a person with a left visual field cut might trip over a chair leg on their left side when walking. They might miss words on the leftmost side of the page when reading. They miss these details because they can no longer see as far to the left when looking straight ahead, as they did before the stroke. People with field cuts can compensate by performing frequent head turns to the side of their blind spot to get the full picture of their environment.
Visual field cuts are usually permanent; however, people with this type of vision loss are often aware of the issue and can learn strategies to function around it successfully.
Visual neglect, hemispatial neglect, and visual inattention are interchangeable terms indicating a lack of awareness of the left or right side of the visual field. Unlike a field cut, a person with neglect is unaware of the missing information and may require a degree of assistance to attend to their neglected side. This condition can extend from one's own body into their environment, affecting ability to process different forms of stimuli including sights, touches, and sounds on the neglected side.
For example, someone with left neglect might seem as if their eyes are always looking to the right and cannot easily move towards the middle or leftward. They might brush only the right side of their hair and think they are finished with the task. They might be startled by a loud sound on their right side, but not react to the same sound on their left.
Neglect causes the brain to have trouble processing information from both sides of the body and environment equally. An occupational therapist can help someone with neglect explore ways to better attend to the neglected side of the visual field or to compensate by bringing neglected information towards the intact side.
If a stroke damages the nerves that control eye movement, the eyes may no longer be able to stay in the same position or move smoothly together. Misalignment of the eyes is known as strabismus. Eye misalignment can cause diplopia, or double vision, as well as blurred vision. A neuro-optometrist may recommend eye movement exercises exercises or issue specially-taped glasses to help strengthen weak eye muscles and correct the alignment.
Will my vision get better after a stroke?
While recovery of vision is possible within the first few months after a stroke, some survivors will experience lingering vision loss or dysfunction. A visual rehabilitation team including a neuro-optometrist and an occupational therapist can help assess visual function and create a comprehensive treatment plan to help make the most of remaining eyesight.
Hepworth, L. et al. “Post-stroke visual impairment: a systematic literature review of types and recovery of visual conditions.” A Quarterly Journal of Operations Research 5 (2016): 1-43.
Visual Problems After Stroke. The Stroke Association. Vision Express. 2018.