Visual field defects are a condition that many people may experience, where there is a loss of sight or restricted vision in one or both eyes. A visual field is defined as the area that can be seen with one eye, or both eyes when open at the same time. In a healthy eye, the visual field should not be limited except by the shape of the eye socket and the head. The visual field extends further towards the ear or side of the head and is reduced towards the nose because the nose obstructs the vision in that direction. A normal visual field with one eye would contain a blind spot from the location of the optic nerve, which does not affect the sight and is not noticeable.
Causes of Visual Field Defects
However, various factors can cause visual field loss, which may significantly impact an individual’s quality of life. Many eye diseases and brain conditions can result in visual field loss, often affecting only the peripheral vision and not the central vision. Common eye diseases that can cause visual field loss include glaucoma, macular degeneration, vein occlusions, and retinal detachment. Brain conditions that can also result in visual field loss include strokes and brain tumors or other masses.
Field Defects from Glaucoma
Glaucoma is a chronic eye condition that gradually damages the optic nerve, which can lead to partial or complete peripheral vision loss. With glaucoma, the peripheral vision tends to be affected earlier than the central vision, and the visual field defects respect the horizontal midline and can either occur only in the upper or lower portion. A person with glaucoma may also experience sudden symptoms such as eye pain, headaches, blurry vision, and rainbow-colored halos around lights.
Vein Occlusion Field Defects
Vein occlusions or blood clots in the retina can restrict blood flow to an area of the eye’s retina, which may cause a visual field loss in one quadrant of a monocular visual field. It appears as an arc. The vision loss may be painless and gradual, but a sudden complete or partial loss of vision may occur with a branch retinal vein occlusion. On the other hand, the central area of the retina is affected by macular degeneration, a chronic eye condition that primarily affects older adults. It causes a blind spot to form in the center of the visual field, making it difficult to read, drive, or recognize faces. There are two types of macular degeneration: “dry” and “wet” macular degeneration.
Stroke Field Defects
Strokes occur when an area of the brain doesn’t receive enough blood flow, which can lead to vision loss. The shape of the visual field defect can indicate where in the brain the stroke occurred. By mapping a visual field in both eyes, it is possible to determine the likely location of the stroke before obtaining neurological imaging. Vision loss from strokes may be sudden or occur gradually and usually occurs in one side of a visual field, although it can affect both eyes simultaneously.
Tumor Field Defects
Any tumor or mass on an individual’s brain has the potential to cause visual field loss based on the size and location of the mass. A common location for tumors that affect vision is the pituitary gland, which can affect the temporal (outside) portion of both visual fields. Symptoms of a pituitary tumor may include vision disturbances, such as double vision or peripheral vision loss.
Treatment for Visual Field Defects
The treatment of visual field loss depends on the underlying cause, and there may or may not be a treatment that can restore vision in the affected area. However, certain measures can help individuals improve their day-to-day experiences and help to increase their level of independence. For example, assistive devices such as magnifiers, telescopes, or glasses can help improve visual field defects. Additionally, special computer software can be used to adjust screen settings or enlarge texts or images. Surgery may also help improve vision loss in some cases, treating conditions such as cataracts and glaucoma.