Presumed ocular myasthenia and micropsia. A case report

Brain imaging in a patient with hemimicropsia

Hemimicropsia is an isolated misperception of the size of objects in one hemifield (objects appear smaller) which is, as a phenomenon of central origin, very infrequently reported in literature. We present a case of hemimicropsia as a selective deficit of size and distance perception in the left hemifield without hemianopsia caused by a cavernous angioma with hemorrhage in the right occipitotemporal area. The symptom occurred only intermittently and was considered the consequence of a local irritation by the hemorrhage. Imaging data including a volume-rendering MR data set of the patient's brain were transformed to the 3-D stereotactic grid system by Talairach and warped to a novel digital 3-D brain atlas. Imaging analysis included functional MRI (fMRI) to analyse the patient's visual cortex areas (mainly V5) in relation to the localization of the hemangioma to establish physiological landmarks with respect to visual stimulation. The lesion was localized in the peripheral visual association cortex, Brodmann area (BA) 19, adjacent to BA 37, both of which are part of the occipitotemporal visual pathway. Additional psychophysical measurements revealed an elevated threshold for perceiving coherent motion, which we relate to a partial loss of function in V5, a region adjacent to the cavernoma. In our study, we localized for the first time a cerebral lesion causing micropsia by digital mapping in Talairach space using a 3-D brain atlas and topologically related it to fMRI data for visual motion. The localization of the brain lesion affecting BA 19 and the occipitotemporal visual pathway is discussed with respect to experimental and case report findings about the neural basis of object size perception.

Visual complaints from healthy children

It is common for healthy children with specific visual complaints to be seen for eye examinations. After a complete eye examination has ruled out pathologic conditions as the cause of these complaints, it is appropriate for the clinician to explore the possibility that normal entoptic or physiologic visual phenomena might have provoked the child's report of vision problems. Some of these normal visual experiences are frequent causes of children's complaints of vision problems, such as physiologic diplopia, relaxation of the near synkinesis during reading, and vitreous body floaters. Some complaints are common, even though the underlying entoptic or physiologic phenomenon may be speculative or obscure, such as the report that objects look bigger or smaller than they actually are. When the clinician encounters such situations, the parents and the child will be much more satisfied by an explanation of the normal system anatomy and physiology than by the simple reassurance that everything is all right.