A tangent screen visual field test performed at 1 meter measures how many degrees?

• A. 60
• B. 30
• C. 20
• D. 45

Answer: (B)

The tangent screen converts linear distances on the screen into visual angles from the fixation point, using the eye-to-screen distance. At 1 meter, the angle theta relates to how far off-center a point is on the screen by tan(theta) = offset / 100 cm.

To reach 30 degrees, the offset would be offset = 100 cm × tan(30°) ≈ 57.7 cm. So the tangent screen at 1 meter is calibrated so that the edge of the tested field corresponds to about 30 degrees of visual angle.

That's why this test, performed at 1 meter, measures 30 degrees of the visual field. Other angles would require edges much closer or much farther than the standard tangent screen setup, which isn’t how this test is configured to be read.