Perimetry is a test to assess the

The visual field is a three-dimensional area of a subject's surroundings that can be seen at any one time around an object of fixation. The extent of the normal visual field with a 5 mm white color object is superiorly 50 degree, inferiorly 70 degree, nasally 60 degrees and temporally 90o degree. The field for blue and yellow is roughly 10 degrees less and that for red and green color is about 20 degrees less than that for white. Perimetry with a red color object is paicularly useful in the diagnosis of bitemporal hemianopia due to chiasmal compression and in the central scotoma of retrobulbar neuritis. Image : Goldmann perimetry Reference : AK KHURANA COMPREHENSIVE OPHTHALMOLOGY, Edition4, Page-481