Visual Field Testing for Glaucoma and Other Diseases

There are various methods to check the visual field and this kind of test is an important tool for glaucoma and other eye conditions which can cause damage to the visual field.

Overview

When a visual field is tested, the goal is to measure how far a person can see in all directions when he or she is focusing in on a central target. The patient is looking at one point, but we want to know how much can be seen beyond and surrounding that target in the periphery. The eye doctor will be able to measure the extent of what you can and cannot see in your visual field and this is known as perimetry

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Visual Field Testing as a Diagnostic Tool

There are various eye conditions and disorders which cause a change or loss of one’s visual field. Testing this aspect of a patient’s vision can help detect eye diseases. Certain conditions cause a loss of visual field in distinct ways such as specific patterns or shapes which make it easier to identify the cause for the loss of one’s visual field. For example, glaucoma causes visual field loss in very specific ways. Testing the visual field can be a crucial tool in diagnosing and monitoring a person’s eye condition.

When to go for Visual Field Testing

If you have an eye disease such as glaucoma or there is reason to believe you might have it, then your eye doctor will test your visual field. After a diagnosis of a disease which affects the visual field, you will continually be monitored to assess the progression of the condition. In glaucoma, there is a typical progression of certain visual field defects and therefore, by testing the visual field, the eye doctor can gain a better understanding of what stage of glaucoma you have.

When to go for Visual Field Testing
Visual Field Testing for Various Conditions

Visual Field Testing for Various Conditions

Visual field testing can be used for a wide variety of diseases which can affect your visual field. Some of these conditions include:

  • Glaucoma
  • Pituitary gland disorders
  • Long term use of certain medications
  • Thyroid eye disease
  • Various brain disorders, including a stroke
  • Multiple sclerosis
  • Optic nerve conditions
Visual Field Testing for Various Conditions

Types of Visual Field Testing

There are different types of visual field testing methods ranging from an approach that does not require equipment to methods that involve very intricate machinery.

  • Confrontation Visual Field Test: This checks overall vision. You will be asked to read from a Snellen chart where the letters decrease in size as you progress down the chart.
  • Perimetry Test: The doctor will see how well your pupils adjust to nearby objects and light, as well as examine external parts of the orbital region.
  • Automated Perimetry: The more common approach used now is the automated perimetry test which involves electronic machines that provide the stimuli and track the patient’s results. This method uses an automated device to map out the visual field, one eye at a time, showing where the patient can and cannot see. The eye being tested will be given its optical prescription to ensure clear vision, while the other eye is covered. The patient looks into the machine at a central target and small dim lights will appear in the peripheral visual field. The person will click on a button each time the light is seen. This allows the eye doctor to track which lights the patient can and cannot see.

There are two methods which are applied for either manual or automated perimetry:

  • Static Perimetry: the shining lights appear in various spots, but remain stationary and do not move across the screen.
  • Kinetic (or Dynamic) Perimetry: this is less commonly used and the lights will move across the screen from a non-visible area to a visible area.
    Standard Automated Perimetry (SAP) is the method most often used which mainly employs the static testing approach. It has a technical software which provides very useful and detailed information about the patient’s visual field which is both seen on the display screen and can be printed. Some of the detailed results received on a SAP machine are particularly useful for glaucoma and the types of damage it causes to the visual field.

Common Questions

There are so many aspects to vision beyond how clearly you can see. One important element of our visual system is our visual field. This represents the ability to focus on a target and still be able to see the periphery. When testing the visual field, the person will focus on a central target and the eye doctor will measure how far and wide the patient can see in the periphery. If the person has glaucoma or other diseases which affect the visual field then the eye doctor will detect that there is a defect in the visual field. This can help diagnose the disease and also monitor its progression.
A person’s visual field is an integral part of one’s overall visual abilities and therefore it’s part of regular eye care. If you are at risk for certain diseases or if there is any suspicion that you may have a condition that affects your visual field then your eye doctor may do a simple initial screening test known as the confrontation visual field test. In this test, the eye doctor will check one eye at a time while the other is closed. You will have to look at a central target and then identify how many fingers the eye doctor is holding up. If there is any suspicion that there might be damage to your visual field then your eye doctor will have more comprehensive visual field testing performed on you, often incorporating automated devices that provide reliable results.
Visual Field Testing for Glaucoma and Other Diseases
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Summary

Visual field testing provides very useful information about a person’s vision capabilities. If there is any damage to the visual field, due to glaucoma or a variety of other diseases, then this test will help diagnose and monitor the condition.

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