eye disorders
The Eye Examination
Visual Field Testing
The visual field is the entire area of vision that is seen out of each eye, including the corners (peripheral vision). The visual field may be tested as a routine part of an eye examination. It may also be tested in detail if people notice specific changes in vision, for example, if they keep bumping into objects on one side. The simplest way to test peripheral vision is for a doctor to face the person and gradually move a finger or another small target (such as a match) toward the person's center of vision from above, below, left, and right. The person tells the doctor when the moving finger or target is first detected. For the result of the test to be valid, the person's vision must be fixed on the doctor's face (and not looking for the finger or target). The eye not being tested is closed. The visual field may be measured in greater detail with atangent screenor aGoldmann perimeter. With these tests, the person stares at the center of a black screen or a hollow, white, spherical device (which resembles a small satellite dish). An object or a light is moved slowly from the periphery toward the center of vision from many different directions. The person indicates when light is first seen out of the corner of the eye. A mark is made on the screen or perimeter indicating where the person can see, thus allowing recognition of blind spots. Visual fields can also be measured using computerized automated perimetry. In this test, the person stares at the center of a large shallow bowl and presses a button whenever a flash of light is seen. is used to test the central area of vision. The grid consists of a black card covered with a white grid and with a white dot in its center. The person notes any distortion in the lines of the grid while staring at the white dot. Each eye is tested at a normal reading distance and while wearing reading glasses, if the person normally uses them. If an area of the grid cannot be seen, an abnormal blind spot may exist. Beyond the area tested by the Amsler grid, there is a normal, small blind spot where the optic nerve leaves the eye. However, people are not aware of this normal blind spot. Wavy lines or a missing area (other than the normal blind spot) suggests a possible problem with the macula. The test is simple enough to be used at home and is useful for monitoring Age-Related Macular Degeneration (AMD or ARMD) . 