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Visual Disorders of Higher Cortical Function Visual disorders of higher cortical function 1Most optometrists are familiar with the myriad of visual percep- tion disorders occurring in infants and children. They are trained to administer and interpret tests that detect these congenital or SARA PENNER ROBERTS, O.D. developmental disorders occurring most frequently in children with ABSTRACT: Following stroke or other learning disability, attention deficit disorder, mental retardation. causes of brain damage, patients may demon- and cerebral palsy. 1 Within the optometric literature, little attention strate visual disorders of higher cortical func- has been given to acquired visual disorders of higher cortical func- tion. These defects involve visual attention, oc- tion that occur in the adult or elderly population as a result of brain ulomotor skills, visuospatial orientation and ob- ject recognition. It is important for optometrists damage from infarction, hemorrhage, trauma, tumor or senile de- to understand these conditions and consider mentia. It is the purpose of this paper to review these neurological their presence in individuals with persistent vis- syndromes of disturbed visual perception and to discuss the impor- ual complaints despite a normal exam, or in tance of their recognition. patients who fail to respond to magnification in Unilateral spatial inattention low vision rehabilitation. The diagnosis and management of these higher order visual dis- Unilateral spatial inattention or neglect is the involuntary failure turbances are discussed. to attend to or respond to meaningful sensory stimuli presented in the affected hemispace.' This phenomenon may occur with any KEY WORDS: hemi-inattention, visual agno- combination of visual, auditory and tactile stimuli. Although this is sia, alexia without agraphia, Balint's syndrome, higher order visual disturbances, rehabilitation, not caused by motor or sensory defects, it is frequently accompanied stroke, brain damage by hemianesthesias, hemiplegias and homonymous hemianopsias. The effect of hemispatial neglect can be devastating. In fact, some Roberts SP. Visual disorders of higher cortical func- tion. J Am Optom Assoc 1992: 63:723-32. researchers cite unilateral neglect as one of the main factors inter- fering with recovery and successful rehabilitation in stroke pa- tients' In severe forms, the patient demonstrates complete hemis- patial neglect to the extent that he may not dress or shave the Roberts, Sara (1992). Visual affected half of the body/ He may not recognize his arm and leg as disorders of higher cortical his own and object to their presence in his bed." Questions addressed function. Journal of the to the patient from the affected side may go unanswered and American Optometric navigation may be difficult if the patient collides with objects and is unable to orient himself to new surroundings.* In its most subtle Association, 63(10)724-732. forms, the patient demonstrates inattention only when faced with a complex task. In these cases, the hemispatial inattention may be detected by presenting the patient with symmetrical simultaneous stimuli (i.e., fingers presented to each side of the mid-line in the THIS IS superior visual field). Failure to detect both stimuli constitutes an COPYRIGHTED abnormal response known as the extinction phenomenon.5.6 Hemispatial inattention is usually the product of a right (non- MATERIAL. YOU dominant) parietal lobe lesion. Left sided parietal lesions are less MAY PRINT ONE commonly reported and are associated with less persistant and COPY FOR YOUR milder forms of inattention.''.7 Rarely there have been other reported OWN USE ONLY! cases of lesions occurring elsewhere in the brain including the frontal lobes, occipitoparietal lobes, cingulate gyrus, thalamus, pu- tamen, basal ganglia and mesencephalon.'J Infarction (stroke) is most commonly implicated, although the phenomenon has been reported in association with hemorrhage, tumor, and traumatic contusion.2 The exact mechanism is unclear. The examiner's assessment should begin with simple observa- tion of the patient. As mentioned earlier, patients with moderate to severe hemispatial neglect may demonstrate peculiar behavioral Volume 63. Number 10. 10/92 723 patterns as they orient their body and activities toward the unaffected hemispace (ipailateral to the side of the lesion). For example, they may comb only half of their hair, fill out only half of the insurance form or read only half of the letters on each line of the acuity chart. The patient's family members or case workers may also be able to provide a history of this type of behavior. A commonly used screening procedure for hemis- patial visual inattention is the double simultaneous stimulation test, which was first described by Oppen- heim using tactile stimuli.2 A standard confrontation visual field is first conducted using single stimuli pre- sented in each quadrant of the visual field, one at a time. If the responses are abnormal (i.e., failure to identify the stimulus), one cannot differentiate between a hemianopic visual field defect and a severe attentional disorder without further testing.* In this case, the dou- ble stimulation test cannot be performed. If the re- sponses are normal, however, the examiner then pre- sents double simultaneous stimuli, placed on each side of the vertical midline. Extinction occurs when the patient fails to perceive the stimulus in the field con- tralateral to the lesion, while correctly perceiving the stimulus in the ipsilateral field. Although sensory ex- Figure 1: The results of the clock completion test, as per- tinction, like hemi-inattention, is typically a product of formed by a person with hemispatial visual inattention. right parietal lobe lesions, it is not pathognomonic for hemi-inattention disorders." In addition, the test sen- sitivity may be as low as 50 percent 9 Pursuit and saccade testing are also easy screening ments of the clock on the side ipsilateral to the lesion procedures that may alert one to the presence of lesions or they will complete only this half of the clock (Fig. that can produce hemispatial inattention. Affected pa- 1). This assymetry in performance allows the examiner tients may demonstrate difficulty when attempting to to differentiate this defect from other visuoperceptual track an object into the affected hemispace and main- or constructional difficulties, and placement of the test tain stable fixation. When asked to alternate fixation in the hemifield free of visual field defect reduces field between two targets on either side of the midline, they loss as a cause of poor performance. Similarly, the may fail to search or demonstrate very slow searching examiner may draw a series of horizontal lines and ask in the hemispace contralateral to the lesion. Optoki- the patient to draw an "X" at the center of each line." netic nystagmus (OKN) reflexes also may be of some Patients with hemispatial visual neglect may fail to benefit as they are typically decreased or absent when cross all the lines on the page, and of those lines which the drum is rotated towards the side of a parietal lobe are crossed, the "bisecting line" is skewed toward the lesion." side of attended space. A visual marker (such as a letter) For patients with concurrent hemianopic or quad- may be placed at the beginning and end of each line rantanopic visual field defects, the double simultaneous and the patient is then instructed to bisect the line only stimulation test cannot be performed, and pursuit/ after naming the letters associated with each line. This saccade testing may not produce reliable results since ensures that the entire line is seen, thereby eliminating abnormal responses may occur as a result of the visual any effect from visual field deficits. field defect alone. For these patients, the clock comple- The Rivermead Behavioral Inattention Test tion test and the line bisection tests are particularly (RBIT) has been developed as a useful method for useful. detecting visual neglect, as well as for estimating its In the clock completion test, the examiner draws a functional impact.'3 The RBIT differs from other tests circle (clock face), and then asks the patient to complete of visual inattention because it uses behavioral meas- the clock by drawing in the numbers and hands. The ures such as eating a meal, reading a menu, etc. ~ test material should be placed in the attended space, Rehabilitation of patients with bemispatial visual opposite the side of visual field loss. Patients with inattention is difficult. A common sense approach to hemispatial visual inattention will either place all ele- training, aa outlined by Bouska, et al., is found in Table 1.' One should keep in mind that although patients may be trained for specific tasks, they may find it hard to generalize and apply these techniques to untrained tasks' In addition, some patients manifest other cog- 724 Journal of the American Optometric Association Table I: Training guidelines for hemispatia visual inattention 1. Attempt to improve patient's awareness and understanding of inattention and/or visual field loss using examples in the environment. 2. Practice visual scanning skills, including ocular pursuit and saccades, into the unattended space. 3. Provide the patient with increasingly complex visual-perceptual and visual-motor tasks which require the integration of the above two points. Figure 2: Patient with apperceptive agnosia demostrating 4. Stress the importance of scanning during activ- inability to correctly match object shapes. (Drawing repro ities of daily living-, reminding the patient, duced with permission from Farah MJ, Visual Agnosia. "when something doesn't make sense, look into Cambridge, Massachusetts: The MIT press, 1990.) the unattended space and it usually will". altogether, claiming that all patients with visual agno- 5. Use visual markers at the end/beginning of the sias would show significant visual pereeptual difficulties page to decrease inattention while reading. if subjected to adequate study."'" For the sake of this discussion, however, we will continue to follow this classification scheme. nitive, motor or sensory deficits that may complicate or prohibit attempts at rehabilitation.
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