Lesions of the optic radiation cause contralateral homonymous defects in the fields of vision. The defect may be quadrantic or hemianopic, with or without sparing of central vision. Sometimes, however, careful perimetric determinations reveal partial and unpaired blind areas, i. e., a defect in one section of the field of vision of one eye but not in the corresponding field of the other eye. The commonest type of unpaired defect in cases of lesions of the optic radiation is known as the temporal crescent or half moon defect. The terms temporal crescent and half moon have reference to either one of the two areas which are temporal and peripheral to the binocular field of vision (fig. 1). Each of these areas is projected on the retina of one eye only (on the nasal retina) and therefore represents the uniocular field of vision. It corresponds to the phylogenetically oldest monocular
BENDER MB, STRAUSS I. DEFECTS IN VISUAL FIELD OF ONE EYE ONLY IN PATIENTS WITH A LESION OF ONE OPTIC RADIATION. Arch Ophthalmol. 1937;17(5):765–787. doi:10.1001/archopht.1937.00850050013001
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