Visual Field Testing for Glaucoma and Other Diseases

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.