Visual Field Testing
The visual field is a complete area that can be seen when your eyes focus on a single point; this comprises of objects that can be seen on either side, and above and below the point that your eyes focus on. Visual field testing are diagnostic tests used to measure the entire scope of vision, which includes the central and peripheral (side) vision.
It is most commonly used to evaluate any damage to the optic nerve. It is also used to detect retinal diseases, drooping of the eyelids and conditions affecting the visual pathways in the brain. The examination helps to determine the loss of vision in the visual field. The visual field examination is performed in different ways:
- Confrontation visual field exam: This is a primary examination, during which the examiner asks you to cover one eye and look straight ahead. The examiner stands at 90 to 100 cm and moves his/her hand towards and away from your field of vision. You are instructed to indicate when you can clearly see the examiner's hand.
- Tangent screen or Goldmann field exam: You are seated about 90 cm away from a screen with a target in the centre. You are instructed to stare at the centre and inform your examiner when you see an object moving into your side vision. Your examiner uses this information to create a map of your field of vision. This helps your doctor detect areas of blindness in your visual field.
- Automated perimetry: You are seated in front of a concave dome and instructed to stare at an object in the centre. You are instructed to press a button when you observe small flashes of light in the peripheral vision. Computer images will help in determining defects in the visual field.
Your doctor will discuss the type of visual field examination to be done.