Not - So - Peripheral Vision

At my office, we do a visual field screening test with almost every standard eye examination. This is sometimes incorrectly referred to as a “peripheral vision test”. My Humphrey-Zeiss automated visual fields tester can measure the visual field out to the far periphery, but during the screening mode it only tests the central 30° of the visual field. The vast majority of the neurological disorders we are looking for will be picked up in this 30° central test.

Two main disorders we are looking for are brain tumors and strokes. Both of these disorders can cause a visual field loss because they disrupt the “wiring” in the visual pathway in the brain. The visual cortex, or “seeing” part of the brain, is located at the very back of the cranium. The “wires” in the visual pathway that connect the retina in the eyes to the visual cortex travel through the parietal and temporal lobes of the brain. The “wires” responsible for the left half of our visual field travel in the right side of the brain, and those for the right half of the visual field travel in the left side of the brain. Therefore, any disruption of the wires (from, say, a stroke or a tumor) on the left side of the brain can cause a visual field loss on the right. Problems on the right side of the brain will manifest in the left half of the visual field. When visual fields are screened, careful attention is paid looking for field loss present in both eyes symmetrically on either the left or right half of the field.