Also known as a visual field test, a perimeter uses a special system to determine and measure the reaction of the eye to different types of light sensitivity. This advanced device comes with a tangent screen, which is a big white screen that is placed in front of the patient’s field of vision. There is also a Goldmann perimeter, which is shaped more like a sphere and uses different types of light to test the sensitivity of the eyes. More features of perimeters include:
- Computerized projection abilities
- Video eye monitors
- Fixation targets
- Alternative options for patients with low vision
- Automatic calibration features
- Stimulus intensity measurements
- Multiple screens and screening abilities
- Selectable tests
- Color options, as well as greyscale
- Convenient LED display
Perimeters typically grant a full field of vision, which is great for testing a number of different eye functions. The ophthalmologist can accurately see the results of the test through a screen, and can chart down the eye’s reactions to the stimulus in real time.
Perimeters use automated or computerized stimuli to test the patient’s field of vision. It is also used to test changes in the vision of glaucoma patients over time. With automated perimetry, the examiner can press a number of single buttons to activate features that will test different parts of the patient’s vision. The computerized perimeter will map out the patient’s visual field in an aesthetic display that is easy for the examiner to read. This happens after the perimeter uses a series of lights on a screen, and the patient must click a button whenever they see the light.