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Vision Disorders in Acquired Brain Injury
By Martin H. Birnbaum, O.D., Michele R. Bessler, O.D.
Many individuals experience severe vision and eye problems as a result of stroke or closed head trauma. Vision disorders commonly encountered include double vision, blur, eyestrain, discomfort when reading, loss of part of the field of vision, dry eye, difficulty with visual judgements in space, and impaired visual memory.
Rehabilitation of eye and vision disorders is often neglected in patients with closed head trauma. Although they are extensively diagnosed, frequently little or nothing is done to treat the problems. This is unfortunate, since visual function can often be improved substantially, with significant relief from visual symptoms.
In recent years optometrists who specialize in vision therapy have become increasingly involved in the rehabilitation of these vision disorders. Optometric intervention plays an important role in the total rehabilitation effort, frequently allowing affected individuals to more adequately perform the varied activities of daily living, and thus to substantially improve their quality of life. We have found working in this area to be extremely gratifying, and are writing this article to share our experience and concepts with colleagues.
Many individuals suffer from double vision, which causes confusion and disorientation. Such individuals are often given an occluder. This resolves the diplopia, but reduced the field of vision and interferes with daily function. Diplopia can often be eliminated without an eye patch, through the use of prisms and vision therapy. This approach not only eliminates double vision, but allows more normal visual judgments in space, and makes movement in space less hazardous.
Many head trauma patients experience difficulty in reading. This may be caused by vergence and accommodative deficits that cause blurred or double vision, jerky eye movements, or visual field loss that makes it difficult to keep one's place. Depending on the specific cause, relief can usually be obtained with appropriate reading glasses, prisms, and vision therapy.
Moving a ruler down the page line-by-line frequently makes it easier to keep one's place when loses of place is caused by jerky eye movements or by visual filed loss. Some individuals find it easier to read and keep place if the field is reduced to a single line of print through the use of a typoscope, a sheet of black cardboard or plastic with a cut-out the size of a line of print.
The typoscope makes it easier to keep lace and to focus by isolating the line that is being read. The patient simply moves the typoscope across each line of print, and then down to the next line.
Visual Field Loss
Head injury often has severe effects on the filed of vision, profoundly affecting the way we perceive the world around us. The field of vision can become impaired in many ways. The two most common are hemianopsia and unilateral neglect.
Hemianopsia is a condition in which one-half of the visual field is lost. Depending on whether it is a left or right hemianopsia, the affected individual sees nothing to the left or to the right of the object he or she is looking at. Individuals bump into walls and doorways, fail to see objects and people in the affected field, knock over cups and glasses, and suffer similar mishaps. Driving, as would be expected, is extremely hazardous.
Unilateral neglect is a condition that is in some ways similar, but in other ways quite different, from hemianopsia. It is caused by injury to the parietal lobe. Although either the left or the right visual field maybe affected, left field neglect (caused by injury to the right side of the brain) is much more common.
Individuals with unilateral neglect, like individuals with hemianopsia, do not see objects on one side, usually the left side in cases of neglect. The frequently bump into walls, doorways, and objects on the left side, and fail to see people and objects to the left. In addition, however, individuals with unilateral neglect may ignore one side of their own body, failing to dress the left side, or to shave or apply make-up to the left side of the face. They may even fail to see the left side of various objects, whether the objects are located I the left or the right visual field. When asked to draw a daisy or a clock, the individual with neglect may place all the petals on the right side of the dais, or cram al twelve numbers of the clock dial onto the right side.
Much can be done to help individuals who suffer from hemianopsia and unilateral neglect. Compensatory strategies are used to minimize the impact of the visual field loss. For example, a patient with a left fields loss should sit at the dinner table, in front of the television, and in other situations, so that the majority of objects of interest in the visual field are situated to the right. When engaged in conversation with someone, the patient with left visual field loss should position themselves somewhat to the left of the person they are talking with, so that the major objects in the filed of vision are to their right. Similarly, the child or adult with left field loss should, in a classroom or theatre, position themselves on the left side of the room (when facing front), so that the bulk of the classroom or stage is in the right visual field.
Individuals with visual field loss should use eye movement scan strategies to look into the lost field to see what is there. For example, a person with a left visual field loss should get into the habit, whenever walking into a room, to scan and look around the left side of the room, to look for and notice objects and people that would otherwise not be seen. Eye movement exercises are frequently helpful in this regard, as are computer programs designed to foster rapid and accurate scanning into the affected field.
Visualization exercises in which the person looks into the affected field to see what is there, and then visualized the objects in the lost visual field in the mind's eye, while looking straight ahead, help to expand awareness of objects in the lost visual field.
Yoked prisms and mirror devices are often helpful in cases of visual field loss. Yoke prisms, with their bases towards the affected field, are used to shift objects from the non-seeing to the seeing filed of vision. Such prisms also frequently redress mismatches between body image and perception of space, so that individuals feel more stable and secure moving through their visual space world. Tiny mirrors affixed to one's spectacles have also been used to aid in scanning into the affected field and expand visual field awareness.
We have found that most individuals with visual field loss do not suffer complete blindness in the affected field, but rather retain the ability to see and respond to objects that are sufficiently bright. Stimulatory exercises in which bright lights are flashed in the affected field are frequently effective in expanding awareness in the "blind" field. A typical sequence for such exercises is as follows:
- Flash a penlight on and off in the affected field. The patient looks straight ahead at the therapist's or spouse's face. When the patient see the light go on in his peripheral field, he touches it with his index finger, while continuing to look straight ahead at the therapist's face. If the light cannot be seen in the affected field, use a brighter light, hold the light closer to the patient's eyes, and turn off the other lights in the room to increase contrast. Flash the light in various areas of the affected field, i.e., at eye level, above eye level, and below eye level.
- Hold two flashlights, one in the normal and the other in the affected visual field. Flash them on and off, one at a time, in random sequence, while the patient looks straight ahead at the therapist's face. When the patient sees either light go on, he touches it with his index finger, while continuing to look at the therapist's face. It is important to flash the lights in a random, unpredictable sequence.
- The therapist holds two flashlights, one in the normal and one in the affected visual field, and flashes sometimes one, sometimes the other, and sometimes both, in a random, unpredictable sequence, while the patient looks straight ahead at the therapist's face. The patient touches whichever light or lights he perceives ad being on, while continuing to look at the therapist's face. The lights are sometimes flashed at eye level, sometimes above, and sometimes below.
These exercises are designed to increase awareness, sensitivity, and utilization of vision remaining in the affected field.
Some patients with acquired brain injury have a normal filed of view, but are unable to read ordinary print or watch television with conventional glasses due to reduced visual acuity, or low vision. Optometric low vision care often allows such individual to overcome this handicap so they can handle daily activities and maintain independence. Low vision aids include sophisticated telescopic lenses for distance vision, and simple magnifying lenses and more complex microscopic and electronic magnifiers for reading and other fine tasks.
If the nerves or muscles of the eyelids are affected by stroke or head injury, the lids may not close fully on each blink or during sleep, causing the gritty, burning secretion associated with dry eye. Dry eye symptoms are typically relieved with the use of carefully selected lubricating drops and ointments. In sever cases, collagen plugs inserted into the tear ducts frequently work to increase lubrication of the eye and eliminate discomfort.
Individuals with acquired brain injury frequently experience unstable orientation in space, so that objects and even the walls and floor are perceived to move and shift about; difficulty with object localization and visual judgements in space; inability to sustain visual attention; and poor visual memory. These functions can often be improved through the use of prisms that restore one's ability to orient himself in space, and rehabilitative vision therapy to improve visual perceptual, spatial, and information-processing functions.
Vision problems resulting from acquired brain injury are often overlooked during initial treatment of the injury. Frequently the vision problems described above are neglected. This lengthens and impairs rehabilitation, results in incomplete treatment, and causes frustration for the patient, family, and treatment team.
Optometric rehabilitation can play an important role in the overall rehabilitation effort. Optometrists who specialize in vision therapy can provide needed treatment that allows patients with acquired brain injury to more easily and adequately perform the varied activities of daily living. Treatment regimens are designed to meet the needs of each individual patient, and frequently incorporate combinations of lenses, prisms, low vision aids, and vision therapy activities to relieve symptoms and increase vision efficiency. Clinical experience and research studies each document the value of optometric rehabilitation for individuals who suffer from vision disorder as a result of acquired brain injury.