Visual Field Tester: How It Works
Exploring Visual Processing and Visual Fields

Visual Processing and Visual Fields

The FieldTester User Interface

Running the FieldTester Applet

References, Links, and Credits

How the Visual Field Tester Works

The FieldTester tries to take into account the complexity of visual processing and the ability of brain trauma victims to understand unfamiliar software programs.

The FieldTester starts by presenting a panel of choices. You can pick the type of test, the number of test items, and several options that customize the test. You can make your selections before the test starts, or stop the test and change the settings at any time.

Exercise Types

The selection panel shows five exercise types, each emphasizing a different part of the visual processing system:

  • Words. Each item in a word test is paired with a similar word with letters missing on the left or right side or in the middle.
  • Lines. Each item in a line test is a straight line. Each line has a slightly different slope.
  • Edges. Each item in an edge test shows the intersection of two lines.
  • Shapes. Five simple shapes are presented, both in outline and solid form.
  • Colors. Each item in a color test presents a circle filled with a solid color. The colors are chosen at random from a palette of 256 non-dithering colors.

Beneath the type selection, you can set the total number of test items for the FieldTester to present. The FieldTester will distribute the test items evenly across the selected types, but the order they are presented in will be random.


You can choose which field is tested, which visual quadrants are tested, and whether the test image stays on the screen.

The FieldTester can test either your left visual field or your right visual field. Which side gets tested is up to you. There are four choices:
  • Left and Right. The FieldTester alternates questions about the left field with questions about the right field.
  • Left Only. The FieldTester asks you only about the left field.
  • Right Only. The FieldTester asks you only about the right field.
  • Random. Which field the FieldTester asks you about is chosen at random.

If you choose Randomize screen locations, the FieldTester will present the items to all six visual field quadrants.

If you choose Flash mode, the images stay on the screen for two seconds before the FieldTester asks you to identify them. Otherwise, they are always visible.

Lou Ceci
Glyphic Technology
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