Visual Field Defects | Causes and Symptoms

Visual field loss, or visual field defects, occurs when there are black or gray areas within a person’s vision. This is usually due to a problem in either the eye or the brain that leads to the loss of part of the visual field.

Inside the eye, conditions such as glaucoma and macular degeneration can cause specific patterns of visual field loss. In the brain, a stroke or tumor may lead to the loss of a quarter or even half of the visual field. Understanding the possible causes of visual field loss helps guide the diagnosis of conditions affecting both the eye and the brain.

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What Is the Visual Field?

Each person has a limited portion of the world they can see at any one time without moving their head or eyes. This area of sight includes central vision and peripheral vision, which together make up the visual field. Any type of vision loss can therefore be classified as a partial or complete defect in the visual field.

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How Are Visual Field Defects Measured?

The brain naturally tends to compensate for any vision loss in one or both eyes by “filling in” the missing areas with its best guess of what should be there. Because the brain adapts so quickly to visual field loss, it may cause no noticeable symptoms at all, or fewer symptoms than expected given how much vision is actually missing.

To accurately determine whether there is any visual field loss, a device called a visual field analyzer or perimeter is used. This test requires one eye to be corrected and focused on a central spot or target. Once these conditions are met, the instrument presents small lights to measure the sensitivity of specific areas within the visual field.

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Visual Field Defects from Glaucoma

Glaucoma causes visual field loss starting in the periphery, which gradually progresses toward central vision. These defects may appear as nasal field loss, arcuate (arc-shaped) defects affecting the upper or lower visual field, or loss of an entire half of the field. Visual field loss from glaucoma often goes unnoticed by the patient, but everyday activities like navigating around objects may become more difficult, and bumping into things may occur more frequently.

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Visual Field Defects from Macular Degeneration

Macular degeneration affects the central part of vision known as the macula. Early on, central vision becomes blurred; as the disease progresses, this area can turn completely dark, creating a central visual field defect.

Because these defects are located in the center of vision, symptoms tend to be noticed quickly and any changes are usually obvious. As macular degeneration advances and the center of vision becomes more damaged, the eye may start to fixate using a non-central point in an attempt to achieve better vision and to work around the large central blind spot.

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Visual Field Defects from Tumors or Strokes

Brain injury in the form of a compressive tumor or a stroke (cerebrovascular accident) can cause visual field defects if the affected brain region is responsible for visual processing. The occipital, temporal, and parietal lobes are key areas where such injuries may result in visual field loss.

These visual field defects are usually symmetrical and respect the vertical and horizontal midlines, because the optic nerve fibers are organized in a specific way once they enter the brain. Based on the pattern of visual field loss alone, an eye care professional or neurologist can often predict the likely location of a stroke or tumor, which is then confirmed with imaging studies.

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Regardless of the type of vision loss, eye defect, or visual problem, this is a delicate medical condition that requires a thorough examination and appropriate treatment by a skilled, experienced ophthalmologist, using effective medical tools and technologies that provide real benefit. Whatever eye disease you may be dealing with, you can book an appointment at Batal Specialized Center for a comprehensive eye evaluation and to begin addressing your eye problems, no matter how complex they may be.

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