[Unawareness for homonymous visual field defect].
BACKGROUND
There was no report which dealt with the relationship between emotional state, degree of defective visual search, severity of hemianopic dyslexia, the episode when the patient became aware of the defect, and unawareness of visual loss in homonymous hemifield.


OBJECTIVE
To investigate the relationship between degree of awareness and those factors that might be responsible for the unawareness, including the aspects listed above.


METHODS
Four patients with visual field defects caused by a brain lesion after a stroke was investigated. Self rating of emotional state, search performance for an object among many placed on a table, and for text reading, as well as visual field, visual positive phenomena, and hemispatial neglect were evaluated. Degree of unawareness for field loss was evaluated by modified version of the method of Bisiach et al. (1985). In addition, the episodes when the patient became aware of the defect were asked.


RESULTS
In accordance with the previous studies, we found no relationship between the degree of awareness of field defect and anatomic lesions, co-existence of hemispatial neglect, or the degree of awareness of hemiplegia. However, the patient with neglect was unaware of their troubles in vision at all, whereas the patients without neglect were aware of the troubles but misinterpreted them as problems of the eyes including acuity. In accordance with previous studies, co-existence of visual hallucinations or illusions seemed to be associated with awareness of visual field defect. No relationship was found between the degree of awareness of field defect and emotional state, degree of field loss, degree of defective visual search, or severity of hemianopic dyslexia. Their responses to the inquiry about the degree of awareness of field defect were not consistent. Thus, the awareness of the field defect seemed to be difficult to be kept firmly in their mind. On the other hand, the patients could remember the episode when they became aware of the defect for the first time, being able to specify time, place, and situation.


CONCLUSIONS
Levine (1990) suggested that the sensory loss in this sort of patients was never phenomenally immediate but instead must be discovered by observation and inference. Non-specificity of the lesion, qualitative difference in awareness between the patient with and without hemispatial neglect, association of positive visual phenomena and awareness, fluctuation of awareness, and dependence of awareness on personal experiences found in our patients, can be explained with this 'discovery' hypothesis.
Ito
Tomoko
T
Division of Neuropsychology, Department of Disability Medicine, Tohoku University Graduate School of Medicine.
Hirayama
Kazumi
K
Yamawaki
Rie
R
Kondo
Yumiko
Y
Sakai
Shinya
S
Kondo
Takeo
T
Yamadori
Atsushi
A
D000368:Aged; D001364:Awareness; D002561:Cerebrovascular Disorders / Q000150:complications / Q000523:psychology; D004411:Dyslexia, Acquired / Q000150:complications; D005260:Female; D006423:Hemianopsia / Q000175:diagnosis* / Q000523:psychology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010468:Perceptual Disorders; D012720:Severity of Illness Index; D014794:Visual Fields