THE THREE MOST DEVASTATING AND INTOLERABLE VISUAL
Visual Field Loss
PROBLEMS RESULTING FROM BRAIN INJURY AND STROKE
Although there are many visual problems that arise from brain injury and stroke, three are more devastating and impairing than the rest. These are visual field loss, intractable double vision, and visual / balance disorders.
With a visual field loss the patient is literally blind to half of their field of vision. This places the person at increased risk of further injury and harm from bumping into objects, being struck by approaching objects, and falls.
A two fold approach is used to treat visual field loss. Visual rehabilitation activities are prescribed by the doctor and administered by the therapist to teach scanning of the hemianopic field loss. In addition to occupational therapy, special visual field awareness prism lenses are used in treating visual field loss. As the patient scans into the prism the optics are shifted so as to perceptually gain about 15 to 20 degrees of visual field recognition. These are used as spotting devices only to determine if there is an object in the periphery that deserves further visual attention. When such an object is spotted, the patient turns their head to view it in detail with their intact central vision.
Double Vision (Diplopia)
Double vision (diplopia) is a serious and intolerable condition that can be seen in patients with brain injury, stroke and other neurologically compromising conditions. Prisms, lenses and / or vision therapy can oftentimes help the patient achieve fusion (alignment of the eyes) and alleviate the diplopia. If and when these means are not employed, the patient may adapt by suppressing the vision of one eye to eliminate the diplopia. If lenses, prisms, and / or therapy are not successful and the patient does not suppress, intractable diplopia ensues.
Visual Balance Disorders
Visual balance disorders can be caused by a Visual Midline Shift Syndrome (VMSS), oculo-motor dysfunction in fixations, nystagmus, and disruptions of central and peripheral visual processing. Lenses, prisms and visual rehabilitation activities are used in the remediation of these disorders.
• Visual Midline Shift Syndrome
º Visual Midline Shift Syndrome results from dysfunction of the ambient visual process. It is caused by distortions of the spatial system causing the individual to misperceive their position in their spatial environment. This causes a shift in their concept of their perceived visual midline. This will frequently cause the person to lean to one side, forward and/or backward. It frequently can occur in conjunction with individuals that have had a paralysis to one side. By using specially designed yoked prisms, the midline is shifted to a more centered position thereby enabling individuals to frequently begin weight bearing on their affected side. This works very effectively in conjunction with physical and occupational therapy attempting to rehabilitate weight bearing for ambulation.
• Visual Hallucinations
º Visual hallucinations may occur both as formed objects like stars or other recognizable objects or may be unformed as in flashes and spots. The formed images may represent misunderstanding of information in the brain or background "noise" from the disruption of brain tissue that is needed to process the information.
º A separate but related cause of visual hallucinations is called Charles Bonnet Syndrome. It occurs in patients with significant loss of vision. The hallucinations from Charles Bonnet Syndrome are often very detailed such as a group of people, a truck or an animal. These are not psychotic in nature but simply represent the brains attempt to interpret the impaired information and find a mental image to match the incoming message.
• Visual Neglect - Visual Imperception
º Cerebral injury from stroke or other trauma may cause visual imperception. It is a passive unconscious decreased awareness of part of the field of view or other stimuli to one side of the body. It usually occurs with a visual field defect, but may occur without loss of field. A person without visual imperception, but with a visual field loss would still be aware of the area of loss and be more likely to make compensations. A person with both visual field loss and visual imperception would unconsciously neglect the area of the field loss and thus be less likely to compensate for the defect.
º Damage to the right side of the brain may cause both visual field loss and visual imperception to the left side. Right brain injury neglect is usually more severe than left brain injury neglect. The most common site for visual imperception is the parietal lobe, but damage to frontal lobe and even the deeper structure (thalamus and basal ganglia) may cause visual imperception.
º The treatment of visual imperception is still limited. It begins with teaching the patient to be aware of the neglected side often through occupational therapy. If the patient has a visual field defect, visual field awareness prism may be beneficial, followed by intense occupational therapy.
Vision Related Side Effects of Traumatic Head Injury
• Field Loss
• Hemianopsia (Loss of half of the field of view to the right or left, or bi-nasal or bi-temporal)
• Quadranopsias ( Loss of about 1/4 sector of the visual field)
• Central Loss
• Sector Loss
• Peripheral Loss
• Total Loss of Visual Field
• Attitudinal Losses
• Reading Disorders
• Diplopia - Exotropia, Esotropia and Hypertropia
• Cranial Nerve Paresis / Paralysis III ,IV, VI , VII
• Small changes in refractive errors more significant
• Dry Eye - Decreased Blink Rate
• Visual Hallucinations
• Accommodative Problems
• Convergence Problems
• Eye Movement Disorders, Fixation, Pursuits
• Frequent Headaches
• Unstable Ambient Vision
• Visual Perceptual Disturbances
• Disturbances in body image
• Disturbances of spatial relationships
• Right - Left discrimination problems
• Agnosia - difficulty in object recognition
• Apraxia - difficulty in manipulation of objects
• 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.
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 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.
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 prism
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 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 specially 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.