More than half of stroke survivors experience visual impairment following stroke. Read on to understand stroke-related visual problems including field cuts, neglect, and double vision.

Stroke Lingo Part 4: Vision Changes After Stroke

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
 1. Visual Field Loss
 2. Visual Neglect
 3. Eye Movement Dysfunction

 Visual Field Loss
The visual field is the entire area the eye can see when in a fixed position.

A view of a park from two normally-functioning eyes. This represents a full,
intact visual field.

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
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.

A half-eaten personal pizza may appear finished to someone with left-sided
visual neglect. Their brain is ignoring the part of the plate that exists in
their left visual field. This person might learn to compensate when eating by
rotating their plate to ensure no food remains. Eye Movement Dysfunction
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.



References

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.