Visual Midline Shift Syndrome
Many patients who have had a stroke, traumatic brain injury, or other neurological insult, experience a somatic and visual shift in their concept of midline. The shift may be lateral, anterior, or posterior, and is usually in the direction away from the affected side. When the visual midline shifts, it causes the person to unconsciously think that the body center is shifted in the direction of the visual midline. In turn, the person will lean toward the midline shift. This can cause problems with balance, center of gravity, weight bearing, transfer, or ambulation (walking).
For example, if a hemiparesis or hemiplegia has occurred, a lateral shift in visual midline may cause the patient to posture laterally away from the affected side. Some patients may have an anterior visual midline shift, causing a forward lean (flexion), or a posterior midline shift, causing a backward lean (extension). When a patient develops a visual midline shift, physical therapy or occupational therapy treatments for balance, transfer, or ambulation may plateau.
Yoked prism glasses are prescribed by optometric physicians skilled in neuro-optometric rehabilitation for patients with midline shift. Yoked prisms alter a patient’s perception of visual space and increase the patient’s ability to transfer their weight to achieve better posture and balance. These therapeutic prism lenses are not compensatory in nature and are usually prescribed for short periods of time each day, in conjunction with physical and/or occupational therapy.
The initially prescribed power and direction of the yoked prism is only a starting point and a higher or lower powered prism may be needed, depending on the patient’s response to the prism and on the level and intensity of therapy. Sometimes the direction of the yoked prism needs to be changed as therapy progresses.
The therapist keeps the prescribing optometric physician informed about the patient’s response to the prescribed yoked prism during therapy sessions. During treatment with yoked prism the patient must maintain visual fixation at a distance of at least 10 to 15 feet away (while being spatially aware of the visual environment). This allows more effective response to the spatial changes induced by the yoked prism. The patient’s muscle tone, fatigue level, and cognitive awareness while fixating, plays an important role in the effectiveness of the yoked prism treatments. In many cases, the full potential of physical and/or occupational therapy can be reached more quickly when yoked prisms are used. Neuro-optometrically prescribed yoked prism lenses have been used effectively for many years at Neuro-Optometric Rehabilitation Programs in hospitals and rehabilitation centers throughout the United States.
NEGLECT “Neglect” is the inattention to, or lack of awareness of, visual space to the right or left and is most often associated with a homonymous hemianopsia. The lesion usually occurs in the right frontal-parietal lobe. Signs of Neglect
- Can’t or doesn’t readily/spontaneously scan into the area of the neglect
- No awareness of a field of loss
- Says doesn’t see out of the eye (on side of neglect)
- Bumps into things on side of neglect
- Misses parts of words when reading
- Misses parts of eye chart line
- Tendency to orient head or body turned away from the neglect, and the patient may ambulate/drift in direction away from the neglect
- Before starting treatment be sure the patient has been examined by an optometric physician who is COVD Board Certified in Vision Therapy and NORA Clinical Skills Certified in Neuro-Optometric Rehabilitation.
- Encourage eye and head movements to the neglected side, including scan board exercises.
- Use closed eye movements toward the neglected side if difficulty with open eye movements in that direction.
- Have patient ambulate around the room in a direction toward the neglected side to reinforce the non-visual map of space on the neglected side.
- Swinging flashlight aimed alternately toward each foot while walking, to enhance vision with motor reinforcement on the neglected side.
- Do not train with screen activity use (TV, computer, Gameboy, etc.). Screen activities do not have a wide field of view and are not spatially stimulating activities.
- Do games like crossword puzzles and real playing card (not computer) games like Solitaire, because these non-computer games involve tactile/sensory input.
- Increase intentional awareness in the area of the neglect. Ex: Have them squeeze a ball on the side of neglect. Have the patient trace a line that extends into the field cut, put their finger at the far side of the line in the area of the neglect, and rub the finger.
- Have the patient look toward the area of neglect with eyes closed and then when the patient thinks he/she is looking toward the neglected side, have the patient open the eyes, so that the patient and the doctor can see how far toward the neglect the patient’s eyes are actually postured.
- Tell patient to forcibly/rapidly move their eyes as far toward the neglect while sensing the feeling of their eyes at the extreme gaze and then see how far toward the neglect they went. Encourage patient to become aware of the feel of their eyes when gazing as far to the left as possible.
- Have patient wear a “beeper-timer” wristwatch to beep at intervals to remind them to scan at regular intervals.
- Once patient has awareness of their neglect, teach ocular scanning for eye movements up to 20 degrees and had turning with ocular scanning when viewing past 20 degrees laterally.
- Therapies to stimulate movement into the area of neglect like balloon catching/tossing, and also searching for predictive (and later non-predictive) stimuli in the neglected field.
- Turning a page at 45 degree angle will help reading ability for some patients with neglect who do not respond to other treatments.
Peripheral Vision Awareness Device
- Once a patient has become aware of their neglect, and has learned compensatory scanning in the direction of the hemianopsia, the Neuro-Optometrist will prescribe a Peripheral Vision Awareness Device to enhance awareness of objects in the lost field. This will help deal with hemianopsia related safety issues and will enhance the patient’s performance of activities of daily living.