Walsh & Hoyt: Traumatic Optic Neuropathies: Visual Field

Visual fields can be obtained only when sufficient vision is present following optic nerve trauma. The visual field, by virtue of the retinotopic organization of the optic nerve, provides an understanding of the localization of optic nerve damage. Within the canal, the pial penetrating vessels that provide blood to the optic nerve are subject to shearing forces at the moment of injury. Since the superior portion of the optic nerve is most tightly bound within the canal, these pial vessels are thought to be the most susceptible to shearing forces. Partial avulsion of the optic nerve at the globe produces visual field deficits that correspond to the site of avulsion. However, there is no pathognomonic visual field loss diagnostic of optic nerve trauma. Visual field testing is useful in documenting the return of visual function following injury. As a practical matter, confrontational visual fields may be the only type of visual field available at the bedside. Recording the ability to count fingers, detect hand motion, or light in each quadrant may crudely quantitate this. Ambulatory patients should be considered for formal visual field testing.