Details of a visual field test

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Some patients with vision problems may have heard of visual field test, which may also be called as automated Perimetry, threshold test, SITA and so on. Performed probably for different reasons, the main purpose of taking a visual field test is to detect or diagnose glaucoma. In the early days, doctors used a tangent screen on the wall to conduct such a test. And later, a manual version of device called the Goldman Bowl Perimeter was used. Nowadays, automated devices are available.

The relationship between visual parts and retina parts

The sensitivity to light on the retina can be vividly considered as a topographical map of a hill. Of course, the most sensitive point is the center, corresponding to the summit of the hill. In the retina, this visual part is formally named as the macula, which explains why macular degeneration is so devastating. As one of the leading causes of blindness, age-related macular degeneration involves serious damage to the eye’s macula. Patients with this disease suffer gradually losses of central vision, whilst their peripheral vision remains intact.

On the other hand, other parts of the map relate more to the peripheral vision, corresponding to the peripheral retina. While most vision tests only involve this part, a visual field test also measures the pathway of the eye nerves through the brain.

Screening test and threshold test

Either a screening test or a threshold test can be called visual field test. Screening test is simpler that it only checks for eye diseases and vision problems in a way similar to blood pressure reading. However, this kind of simple test can not detect certain visual disorders like higher-order aberrations. Of course, regular visual refractive errors can be detected. In contrast, a threshold test performed by an eye doctor will compare the patient’s results with samples of age-matched population without glaucoma and other eye diseases, generating a detailed statistical analysis. Its name has exactly described the key point.

The time and operational details

The whole process of a visual field test usually takes 30 to 60 minutes, most of which is actually spent on eye dilation. The test itself only costs 3 to 5 minutes in most cases. During the test, corrective lenses will be offered if the patient needs vision correction. Receiving a visual field test requires no effort and there is not any pain. In fact, the patient is just simply required to click a mouse-like device, which indicates his or her response to the flash of light he/she perceives. Light flashes and bright spots will come into the patient’s visual field randomly. In some cases, the doctor will give a demonstration period first.