|Year : 1972 | Volume
| Issue : 4 | Page : 181-182
VN Raizada, IN Raizada
Department of Ophthalmology, L. L. R. M. Medical College, Meerut, India
V N Raizada
Department of Ophthalmology, L. L. R. M. Medical College, Meerut
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raizada V N, Raizada I N. Visual agnosia. Indian J Ophthalmol 1972;20:181-2
Involvement of associational areas for the vision are responsible for this disabling condition. The lesion in such cases is usually very extensive and the poor general condition of the patient may attract all the attention of the physician and the agnosia may be missed initially. Visual agnosia occurring in old age may be more disabling than acquired blindness. An interesting case of cerebrovascular accident in which complete recovery occured except for visual agnosia and amnesia for past events is reported.
| Case Report|| |
History was obtained from the wife of the patient who has been with him through his illness. The patient has loss of memory for all the past events including his illness. He was diagnosed as a case of diabetes mellitus in 1961, the investigations were done on the advice of a doctor friend who noticed polydipsia. Diabetes was controlled with oral antidiabetic drugs, there was no history of high blood pressure at that time. In October 1970, one day the patient was aroused from his noon nap for lunch and his behaviour was found to be slightly abnormal but nothing very striking. In the evening of the same day, the patient noticed diplopia and he was immediately taken to the hospital for treatment. Examination revealed B.P. 170/120 mm. Hg. and right hemiparesis. Visual agnosia was detected by the treating physician on the second day of the admission. The patient fully recovered from hemiplegia but he was greatly disturbed by visual agnosia and was taken to many places for consultation before attending the hospital.
Examinations of his eyes showed no positive finding in the anterior segments, ocular movements were full and eyes were orthophoric. Pupillary reactions were normal both for light and near reflex. The visual acuity, as tested by asking the patient to copy the alphabets, was 6/12 (approximately) both eyes. Fundus was normal. Field charting was very much affected by periods of lack of attention the patient had during testing, still the finding confirmed right homonymous hemianopia, involving the fixation point. The fields were incongruous. He was shown familiar objects and asked to describe them. There was complete inability to recognise even the most familiar objects. He could recognise the objects by touch easily. Such tests confirmed visual agnosia.
| Discussion|| |
Light sensations are carried through the visual pathways to the visual cortex in the occipital lobes. Even at the level of the occipital lobes only the primary visual patterns are appreciated. Sensory impulses received by the associational areas are correlated with the past experiences and interpreted in that light. MULLERS (1923) suggested three levels to explain this complex process; (1) Preipheral level, extending from retina to calcarine cortex, (2 a Middle level constituting the formative zone where primary sensory patterns are built from the sensory data provided and (3) a highest psychological level where they are correlated and associated with previous experiences. It means that disturbances can occur at three levels, at the level of reception of sensory impulses by calcarine cortex, at the formative zone and at the highest level where data is correlated with past experiences and interpretation enters the consciousness into a definite meaning. LissAEVR (1890) divided this process into two parts, (1) Apperception i.e. conscious appreciation of primary sensory pattern and (2) Association i.e. act of linkage with other patterns. Lesion of occipital lobe gives rise to cortical blindness and that affecting the associational areas to agnosia.
Visual agnosia is a disorder of associational areas. Agnosia has been defined as a failure to recognise sensory impressions although their perception is intact. In visual agnosia there is inability to recognise familiar objects by sight, although the object is clearly seen. The patient may recognise the object with the help of other senses e.g. touch. The exact site of lesion is still disputed but COGAN (1966) has localised visual cognitive functions in angular gyrus and to some extent in supramarginal gyrus.
The present case demonstrated typical visual agnosia, associated hemiplegia and lack of any other positive finding denoted arteriosclerosis as the causative lesion. Though some improvement occured in a period of one year, it was too marginal to be of any real benefit to the patient. Resentment of the patient to be taught like a baby was another reason in our not being able to help him fully. It required repeated explanations that the pathology was lying with his brain and not with his sight and change of glasses would not help him. In such permanent lesions there is not much that an ophthalmologist can do except to advise on rehabilitation.
| Summary|| |
A case of visual agnosia with hemiparesis is reported. Hemiparesis later on completely recovered leaving the patient still completely disabled due to visual agnosia.
| References|| |
Cogan, D. G.: Neurology of Visual System, pp. 259, (1966).
Lissauer (1890): Quoted by DukeElder in System of Ophthalmology, Vol. XII, Pp. 480, Edited by S. Duke-Elder.
Muller, G. E. (1923) : Quoted by Duke-Elder in System of Ophthalmology, Vol. XII, pp. 479.