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Vision Related Side Effects
of Traumatic Head Injury
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Field Loss
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Hemianopsia (Loss of half of the field of
view to the right or left, or bi-nasal or bi-temporal)
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Quadranopsias ( Loss of about 1/4 sector
of the visual field)
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Central Loss
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Sector Loss
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Peripheral Loss
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Total Loss of Visual Field
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Attitudinal Losses
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Photophobia
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Reading Disorders
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Diplopia - Exotropia, Esotropia and
Hypertropia
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Cranial Nerve Paresis / Paralysis III ,IV,
VI , VII
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Small changes in refractive errors more
significant
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Nystagmus
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Lagophthalmos
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Dry Eye - Decreased Blink Rate
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Visual Hallucinations
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Anisocoria
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Accommodative Problems
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Convergence Problems
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Eye Movement Disorders, Fixation, Pursuits
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Frequent Headaches
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Unstable Ambient Vision
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Visual Perceptual Disturbances
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Disturbances in body image
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Disturbances of spatial relationships
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Right - Left discrimination problems
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Agnosia - difficulty in object recognition
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Apraxia - difficulty in manipulation of
objects
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Memory Loss
Reading Problems & Traumatic
Brain Injury
Reading problems may occur from
various problems after a stroke or head injury. It is
crucial that the type of reading problem be diagnosed.
The list below contains some of the more common causes
of reading problems after brain injury with introduction
to how they may be treated. The problems may occur
individually or be part of a constellation of problems
related to Post Trauma Vision Syndrome. Treatment of
PTVS through various neuro-optometric rehabilitative
interventions may resolve many of the problems below.
Post Trauma Vision Syndrome
Essentially, individuals with PTVS
begin to look at paragraphs of print almost as isolated
letters on a page and have great difficulty organizing
their reading ability. It has been found that the use of
prisms and bi-nasal occlusion can effectively
demonstrate functional improvement, while also being
documented on brain wave studies by increasing the
amplitude (this is like turning up the volume on your
radio).
Reading Problems Due to Visual Field Loss
Field loss patients often lose
their place in reading. Simple techniques, like boundary
marking, sticking a Post-it note along the side of a
column of print, can mark the beginning or end of the
column and reduce confusion.
Convergence Disorders Affecting
Reading
Patients may experience reduced
convergence after stroke or head injury. Our eyes must
turn in together accurately as a team to prevent double
vision and eye fatigue in reading. Prisms may aid some
patients. Orthoptic therapy may aid some, but not all
patients with convergence insufficiency will respond
fully to therapy due to the variation in the extent of
trauma which may be present.
Loss of Accommodation (Focusing)
Affecting Reading
Young head injury patients may
experience decreased focusing ability. It is often
missed because at an early age doctors don't expect loss
of accommodation. It happens naturally at about age 42.
Individual with reduced accommodation may benefit from
bifocals.
Alexias /Word Blindness
Affecting the Ability to Read
If the patient is unable to read
due to damage to areas which process reading, but can
understand verbal reading, electronic machines are
available that scan all typed print, interpret it and
read it aloud to the patient. Talking books and reading
radio are also very helpful.
Loss of Cognitive Skills May
Affect Reading and Comprehension
Patients may need to relearn their
reading skills developed in childhood or the damage may
be so severe as to preclude reading. Therapists may be
able to re-establish reading over time. Low Vision
Causing Reading Problems When visual acuity is
significantly impaired, high add bifocals or low vision
devices may be indicated. Magnifiers, Electronic
Magnification CCTVs, particular and microscopic eye wear
may help the patient read again.
Diplopia Causing Disruptions to
Reading
If the binocular vision problem can
be treated, therapy, surgery or prisms may be used to
re-establish binocular vision. If the double vision is
not curable, then occlusion may be required. Partial
semi-opaque occlusion may reduce diplopia while
minimizing the disruption to ambient vision caused by
total opaque.
Eye Gaze Disorders
Patients with inferior gaze paresis
may not be able to look down into the bifocal, but may
read with single vision reading eyewear.
Eye Movement /Tracking Disorders
Affecting Reading
Eye movement disorders may also
interfere with reading. As we read down a line of words,
we must make a series of accurate jumps from one group
of words to another. As our head or the paper moves, we
must make rapid adjustments of our eye position. These
rapid eye movements are mediated by the vestibular
system.
Unstable Ambient Vision
Brain injury patients may present
with vertigo, sensitivity to light and extreme
sensitivity to motion around them. Trying to sustain
reading becomes very difficult. The patient may
experience nausea, loss of attention, difficulty
fixating on the words and fatigue. Unstable ambient
vision is a hallmark of Post Trauma Vision Syndrome.
Light Sensitivity after Brain
Injury
Brain injury is often accompanied
by increased light sensitivity and general inability to
tolerate normal glare. The problem seems to be an
inability of the brain to adjust to various levels of
brightness. It is as if one had a radio and the volume
control was broke and you could not make the adjustments
you normally do to control loudness.
Dry Eye Syndromes and Altered Tear / Lid Function
Our eyelids work much like the
windshield wipers on our cars. The lids wipe across our
cornea cleaning it and constantly restoring a new layer
of tear film. If the cornea is not kept moist, a dry eye
may develop. It is much like chapped lips and leads to
dry, burning, gritty eyes. After brain injury, the rate
of blinking may slow and the completeness of the blinks
may decline. The patient may be making only occasional
partial blinks. This leaves the lower portion of the
cornea to dry and become uncomfortable. The simple
addition of artificial tears and reminders to the
patient to blink fully and frequently can manage this
problem. In severe cases, silicone tear duct plugs may
inserted to reduce the loss of tears from the eye down
the normal draining tubes.
Balance & Illusions of
Movement
Dizziness and Balance Problems Related to Vision
Vision plays a significant role in
balance. Approximately twenty percent of the nerve
fibers from the eyes interact with the vestibular
system. There are a variety of visual dysfunctions that
can cause, or associate with dizziness and balance
problems. Sometimes these are purely visual problems,
and sometimes they are caused from other disorders such
as stroke, head injury, vestibular dysfunction,
deconditioning, and decompensation.
Visual Dysfunctions
Causing Dizziness and Balance Problems
Aneisokonia
Aneisokonia is a condition where an
excessive difference in prescription between the eyes
causes a significant difference in magnification of
images seen between the eyes. When this magnification
difference becomes excessive the effect can cause
disorientation, eyestrain, headache, and dizziness and
balance disorders. Treatment is with contact lenses, or
special magnification size matched lenses called
isokonic lenses.
Vertical Imbalance
Normally the eyes work in perfect
synchrony. However, following trauma, fever, stroke,
deconditioning, or sometimes for no apparent reason, one
eye will aim higher than the other will. When mild and
not enough to cause double vision this is called
hyperphoria. If excessive to the point of causing double
vision, it is termed hypertropia. In an effort to adjust
to the vertical misalignment of the eyes, the person
will frequently tip their head to mechanically help
align the eyes. This in turn can cause disorders in the
fluid of the inner ear and resultant dizziness and
balance disorders. Treatment is with therapy to correct
the muscle imbalance and prisms.
Binocular Vision Dysfunction
Binocular vision refers to how the
eyes work together as a team. It is the coordination of
convergence and divergence (eye teaming and alignment)
with accommodation (focusing). Following trauma, fever,
stroke, deconditioning, or sometimes for no apparent
reason dysfunctions can occur causing the eyes to be
weak or overactive. When this occurs, the eyes will
manifest a tendency to drift outwards or inwards. This
in turn can cause eyestrain, double vision, muscle spasm
and excessive peripheral visual stimulation, which in
turn can trigger dizziness and balance problems.
Treatment is with lenses, prisms and therapy.
Double Vision
Double vision is among the most
disorienting and devastating vision disorders. People
suffering from double vision will often times go to
great lengths to alleviate the double image because it
is so bothersome. Many will actually even patch, or
cover an eye, thereby eliminating the vision from one
eye just to get rid of their double vision. Double
vision is caused when the two eyes do not align, or work
together and one eye actually turns out, in, up, or down
compared to the fellow eye. The overall encompassing
term for this is strabismus. The disorientation from
double vision will frequently trigger dizziness and
balance problems. Treatment is with lenses, prisms,
therapy, partial selective occlusion and rarely surgery.
Ambient Visual Disorder
The ambient visual process
frequently becomes dysfunctional after a neurological
event such as a Traumatic Brain Injury (TBI) or Cerebral
Vascular Accident (CVA). Persons can often have visual
symptoms that are related to dysfunction between one of
two visual processes: ambient process and focal process.
These two systems are responsible for the ability to
organize oneself in space for balance and movement, as
well as to focalize on detail such as looking at a
traffic light. Distortions of the spatial system may
cause an individual to misperceive their position in the
environment. This in turn can cause dizziness and
balance problems with the person showing a tendency to
lean to one side, forward and/or backward. Treatment is
with designed prisms and partial selective
occlusion. These techniques work effectively in
conjunction with physical and occupational therapy
attempting to rehabilitate weight bearing for
ambulation.
Eye Movement Disorders
Eye movement disorders typically
show up as instability of visual gaze (nystagmus),
jerkiness of pursuits (eye tracking), or jerkiness of
saccades (visual scanning). Eye movement disorders may
be congenital, or acquired. When acquired, some of the
typical causes are brain injury, stroke, vestibular
dysfunction, multiple sclerosis, and other neurological
disease or disorder.
When there is an acute adult onset of nystagmus the
brain does not register that it is the eyes that are
shaking. Rather, the brain interprets that it is the
world and objects in it that are moving. This is called
oscillopsia and will frequently cause dizziness and
balance problems.
As always, treatment is first aimed at correcting (if
possible) the underlying cause for the nystagmus, or
other eye movement disorder. Concurrently, the following
neuro-optometric rehabilitation approaches may be
helpful.
If there is diplopia, prism, and/or partial selective
occlusion is indicated. Visual exercises may also help
expand the range of single binocular vision. Head
position and direction of gaze may help compensate for
the oscillopsia by finding a null point where the
nystagmus is decreased. Partial selective occlusion can
be helpful where (typically) the nasal or temporal
aspect of the lenses in eyeglasses is partially
occluded with tape. A centimeter or less is usually
sufficient. Nasal occlusion helps improve peripheral
ambient vision, and temporal occlusion helps block
peripheral stimulation. Low amounts of base-in prism can
also help stabilize peripheral vision and thereby help
the oscillopsia.
Accommodative (Focusing) Problems
To change our focus from distance
viewing to near for reading, our brain must interpret
how far away the object in space is located and then
send a signal to the ciliary muscle inside our eye
causing it to change the shape of the crystalline lens
to exactly focus for that distance.
Our focusing ability is greatest in childhood and
progressively declines throughout most of our life until
after age forty, the focus has declined to require
reading lenses or bifocals. Trauma to the brain may
reduce the ability to focus accurately in young people
and may lead to the need for reading correction or
bifocals. Spasms of accommodation may occur causing over
focusing and may present as a temporary increase in
myopia.
Post Trauma Vision Syndrome may impair our ability to
interpret spatial relationships and accurately
coordinate the focus and convergence mechanism.
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