The visual field is the total area an individual can see while their gaze is fixed on a single point, encompassing both central and peripheral vision. A vertical line passing through the point of fixation divides this space into the left visual field and the right visual field (RVF). A restricted RVF refers to a loss of vision in the space to the right of the center point, affecting the perception of space in both eyes simultaneously.
The Visual Pathway: Processing the Right Visual Field
The brain processes the right visual field (RVF) using the left side of the brain. Light from the RVF strikes the inner (nasal) half of the right eye’s retina and the outer (temporal) half of the left eye’s retina. Specialized cells convert this light into neural signals that travel along the optic nerves.
These nerves meet at the optic chiasm. Here, fibers from the nasal retinas, which carry RVF information, cross over to the opposite side of the brain. Fibers from the temporal retinas remain on the same side. This crossing ensures that all signals from the entire RVF are consolidated into the left optic tract. The information then travels to the left lateral geniculate nucleus (LGN) of the thalamus, through the optic radiations, and terminates in the primary visual cortex in the left occipital lobe.
Causes of Restricted Right Visual Field
A restricted right visual field is known as right homonymous hemianopia, meaning vision loss occurs in the corresponding right halves of the visual field of both eyes. Since the visual fibers carrying RVF information have already crossed at the optic chiasm, damage causing this loss must occur after the chiasm, along the left-sided visual pathway. The most frequent cause in adults is a cerebral infarct, commonly known as a stroke.
Damage to the left optic tract, the left lateral geniculate nucleus, the left optic radiations, or the left occipital lobe can all result in this condition. The specific location of the injury determines the exact pattern of loss. For instance, damage limited to a portion of the optic radiations may cause a quadrantanopia—a loss of only the upper or lower right quarter of the visual field.
Non-vascular causes include brain tumors, which compress visual pathway structures, or traumatic brain injuries. Lesions in the occipital lobe often spare the very center of vision, known as macular sparing, due to the dual blood supply to that area.
Recognizing and Testing for Visual Field Deficits
The loss of the right visual field significantly affects a person’s ability to navigate and interact with their environment. Individuals often bump into objects on their right side or have difficulty locating items placed to the right of their central gaze. Activities like reading become challenging because the right half of the visual field is needed to find the beginning of the next line of text.
Initial detection of gross visual field deficits is often accomplished using the confrontation visual field test. During this screening, the examiner compares the patient’s field of vision to their own by presenting targets, such as fingers, from the periphery into different quadrants. This quick test is effective for finding large areas of missing vision.
For a more detailed and precise mapping, clinicians use automated perimetry. This involves the patient looking into a bowl-shaped instrument while small lights of varying intensity are flashed at different points in their visual field. The resulting map helps delineate the boundaries of the field loss and localize the exact site of the brain lesion.