A perimeter capable of objectively adding useful testing points without relying on an operator's intuitional judgment, and capable of performing a reliable test of the field of vision without imposing a useless burden on a subject. The perimeter includes a CPU 11 and a display portion 18. The CPU 11 forms data, which include estimated values, on a visual field characteristic distribution by making an interpolation between tested values of a subject's eye which are obtained by exhibiting a plurality of targets. The display portion 18 displays an unreliable distribution WP indicating a domain estimated to be distant from the tested values on the basis of data on the visual field characteristic distribution and data, which include the tested values, on a distribution of an estimated neighborhood of the tested values.
Perimeter