Visual Field Testing
The visual field refers to your total area of vision, from the centre to the periphery in all directions. Visual field tests (perimetry) are used to measure the integrity of the visual field, and are important for evaluating the retina, optic nerve and visual pathways within the brain.
A number of different visual field examinations are available; which test to use will depend on the clinical indication and the circumstances under which the testing is conducted:
- Automated perimetry: You are seated in front of a concave dome or screen and instructed to stare at a fixation target in the centre with one eye whilst the other eye is occluded. When the testing begins, a small light or pattern stimulus will appear, one at a time, in random locations of the peripheral visual field. You are asked to press a button when you observe one of these lights or patterns. Based on your responses, the computer analysis can determine whether the peripheral visual field is within normal limits or abnormal. Your doctor will interpret the results and discuss them with you.
- Confrontation visual field exam: This is a primary examination, often used for screening or rapid assessment, during which the examiner asks you to cover one eye and look straight ahead. The examiner stands at a distance of approximately 1 metre 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 1 metre 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.