The central visual field of only 10-20 degrees can be tested using plain white paper at a distance of 57 centimetres and a dark pen. Draw a cross in the middle of the paper and ask the person to look toward the centre of the cross all the time, independent of whether the actual crossing point is seen or not. Move the pen from the side of the paper toward the cross and ask the person to say when the pen becomes visible at the edge of the tubular field. Measure the extent from the right, left, up, down and diagonally. Then draw a line through these points and you have the size of the visual field depicted by that oval area. At 57cm each centimetre on the paper equals one degree of visual angle, so you can measure the size of the visual field simply by measuring the size of the area in centimetres. When the visual field is very limited, you may like to use a longer distance, 114cm or 228cm to make the measurement even more exact. At 114cm 2cm equals to one degree of visual angle and at 228cm 4cm equals to one degree.

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