Four types of visual field testing methods
Also called side vision, people’s full horizontal and vertical vision range can be determined by a visual field test. In addition to the evaluation of one’s vision range, such a test can also detect underlying blind spots in the visual field. Visual field-related defects such as blind spots can be caused by a variety of eye and brain disorders. For example, glaucoma, toxic exposure and retina damage can cause optic nerve damage and blind spots. Brain strokes and tumors may also affect the visual field.
Confrontation visual field test
A confrontation visual field testing can detect potential eye diseases and suggest a further test. This test requires the patient to fixate on the doctor’s eye and describe the different numbers of fingers, which are within the patient’s peripheral viewing field but at the far edges. More specifically, the patient will be asked to cover one eye and stare at the examiner, who will then move the hand out of the patient’s visual field and then bring it back in. confrontation visual field test is a simple and preliminary test.
Automated perimetry test
Automated perimetry test can evaluate people vision field by flashing random lights of different strength (generated by computer) into the patient’s peripheral vision field when his or her eyes are staring on a source light straight ahead. The patient uses a button to indicate the presence of objects. There may be a blind spot, if the patient fails to see objects in certain portion of the visual field. This test also requires the patient to cover the eye not being tested. Sitting in front of a concave dome with a target in the center, the patient will receive light shines.
Visual field test using flickering colored bars
A third exam involves the use of doubled contrasting colored (such as black and white) bars, which will flicker at different frequencies during the test. They are supposed to test the response of patient’s photoreceptors within the retina. Optic nerve damage or vision loss at certain areas of the visual field can be detected if the patient fails to see bars at certain frequencies.
Electroretinogram can help in evaluating visual field
There is still a fourth method for testing one’s visual field. Based on the anatomical relationship between the retinal images and the visual field, a device will be placed on the patient’s cornea to detect its electrical impulses, which are in turn used to detect the retina’s response. This method is called electroretinogram. In order to ease any discomfort, the patient’s cornea will be administered with a topical anesthetic before the test.