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S. Nakadomari, A. Furuta, I. Murakami, S. Miyauchi; Retinotopic Mapping for a Patient With Metamorphopsia. Invest. Ophthalmol. Vis. Sci. 2007;48(13):945.
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We previously reported on a patient with cerebral metamorphopsia. Structural brain imaging revealed a lesion in the right lateral occipital lobe. To identify its locus on a functional map and to investigate the relationship between the lesion and perceptual/cognitive dysfunction, we conducted retinotopic mapping using fMRI and several psychological experiments, along with more extensive investigation on visual dysfunctions.
We examined his visual functions as follows: 1) Visual acuity and visual field, 2) Eye movements and optokinetic nystagmus, 3) Basic form recognition, 4) Motion perception, 5) Perception of reflected light from a cylindrical surface, 6) figure recognition from Mooney face illusion. For fMRI, we applied the standard phase encoding technique to obtain the retinotopic map by using a composite visual stimulus consisting of expanding rings and rotating wedges; we also used moving random dots as an MT localizer. His visual field and local hemodynamic delay were estimated by fMRI with this composite stimulus, but additionally, the 4-second full-field stimulation technique was also performed for measurement of hemodynamic delay. We used mrVISTA (Stanford Univ.) and mrFA (custom software) for data analysis.
In the clinical tests he showed: 1) Normal visual acuity and left inferior quadrantanopic sinking for both eyes, 2) Normal eye movements and optokinetic nystagmus, 3) Normal basic form recognition, 4) Normal motion perception except for slight deficiency on recognition of structure from motion, 5) Abnormal perception of the reflected light from a cylindrical surface, 6) Marked disturbance of figure recognition from Mooney face illusion. Functional and structural MRI data revealed that the patient's lesion was located on the area posterior to MT and included right LO and the fovea projection zone. FMRI perimetry showed a left lower quadrant scotoma in central 4 degrees. Hemodynamic delay of the area representing the left lower field was slightly longer than those of other quadrants.
fMRI perimetry and hemodynamic delay measurement showed a functional damage in the area associated with the left lower field in which the patient saw distortion of the object. These results suggest that the cortical damage in the right LO and fovea projection zone may be critical to metamorphopsia.
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