Walsh & Hoyt: Masqueraders of the Optic Chiasmal Syndrome

Manchester and Calhoun reported bitemporal visual field defects in five patients with dominant hereditary optic atrophy. These and similar patients more likely had cecocentral scotomas, diagnosed by the crossing of the vertical midline and association with more severely reduced visual acuity than would be expected from the field defect alone. Similarly, cecocentral scotomas from toxic, metabolic, or other hereditary optic neuropathies can be confused with bitemporal hemianopias. Patients with nasal fundus ectasia may also have temporal field defects, which can be confused with the optic chiasmal syndrome. These pseudotemporal field defects can be distinguished by their failure to respect the vertical meridian and their diminution when minus refractive lenses are used in the perimeter. Since it is not uncommon for the pituitary gland to be physiologically convex, it behooves the clinician to search for other causes of bitemporal defects when the chiasm is radiographically normal and the visual field defects are atypical.