Ventral view of the brain, correlating patterns of visual field loss with the sites of lesions in the visual pathway. The visual fields overlap partially, creating 120° of central binocular field flanked by a 40° monocular crescent on either side. The visual field maps in this figure were done with a computer-driven perimeter (Humphrey Instruments, Carl Zeiss, Inc.). It plots the retinal sensitivity to light in the central 30° using a gray scale format. Areas of visual field loss are shown in black. The examples of common monocular, prechiasmal field defects are all shown for the right eye. By convention,. | Chapter 029. Disorders of the Eye Part 5 Ventral view of the brain correlating patterns of visual field loss with the sites of lesions in the visual pathway. The visual fields overlap partially creating 120 of central binocular field flanked by a 40 monocular crescent on either side. The visual field maps in this figure were done with a computer-driven perimeter Humphrey Instruments Carl Zeiss Inc. . It plots the retinal sensitivity to light in the central 30 using a gray scale format. Areas of visual field loss are shown in black. The examples of common monocular prechiasmal field defects are all shown for the right eye. By convention the visual fields are always recorded with the left eye s field on the left and the right eye s field on the right just as the patient sees the world. The crux of visual field analysis is to decide whether a lesion is before at or behind the optic chiasm. If a scotoma is confined to one eye it must be due to a lesion anterior to the chiasm involving either the optic nerve or retina. Retinal lesions produce scotomas that correspond optically to their location in the fundus. For example a superior-nasal retinal detachment results in an inferior-temporal field cut. Damage to the macula causes a central scotoma Fig. 29-3B . Optic nerve disease produces characteristic patterns of visual field loss. Glaucoma selectively destroys axons that enter the superotemporal or inferotemporal poles of the optic disc resulting in arcuate scotomas shaped like a Turkish scimitar which emanate from the blind spot and curve around fixation to end flat against the horizontal meridian Fig. 29-3C . This type of field defect mirrors the arrangement of the nerve fiber layer in the temporal retina. Arcuate or nerve fiber layer scotomas also occur from optic neuritis ischemic optic neuropathy optic disc drusen and branch retinal artery or vein occlusion. Damage to the entire upper or lower pole of the optic disc causes an altitudinal field cut that follows the .
