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What Is a Visual Field Defect?

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  • Written By: Felicia Dye
  • Edited By: Heather Bailey
  • Last Modified Date: 17 November 2014
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    Conjecture Corporation
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Unless a person is blind, she should be able to see a certain amount of her surroundings. There are standards regarding this ability that are considered normal. Those standards are referred to as a field of vision, or visual field. When a person’s ability to see her surroundings does not meet the standards, she can be diagnosed with a visual field defect. Such a condition could be caused by glaucoma, macular disease, or an aneurysm.

To understand what a visual field defect is, it may be helpful to think of a view as it is seen through binoculars. The two circular areas that are shown can be considered the visual field. A person’s visual field should include the ability to see a certain amount vertically and horizontally. A field vision defect could, in this case, be diagnosed if some part of the visual field is blocked.

Defect, in this sense, means an ability that is partly defective. Blindness is not considered a field vision defect. This is because blindness tends to involve complete inability. It is possible for a person to have a visual field defect without realizing it. This can cause the person to have accidents that may be viewed as clumsy mistakes.

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The causes of a visual field defect can greatly vary. Often, there are certain causes associated with the various types of defects. For example, a peripheral visual field defect could be caused by glaucoma or retinal detachment. If there is a central field defect, this could be caused by macular holes or cone dystrophies. Lesions, which can occur anywhere is a person’s visual pathway, are a common cause of a variety of such defects.

If a person seeks medical attention for such a condition, there are some pieces of information that she is likely to be asked to provide. The ophthalmologist will likely want to know when and how the problem arose. Patients are also generally asked to describe what they are experiencing. This can include the degree or manner in which objects look deformed and whether the problem occurs with both eyes.

There are several methods to test whether a person has a visual field defect. Direct confrontation refers to basic testing methods that involve introducing objects such as fingers or a light into a person’s visual field and having her provide feedback about what she sees. There are more specialized tests, however, such as electroretinography. This testing method uses electrodes to assess activity in the retinas.

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