A metallic graduated scale with a movable pin-punch pointer is fixed to mark on the perimeter chart paper. The perimeter is an instrument for accurate charting of the field of vision. It consists of. A vertical stand on which a metallic arc is pivoted. It also bear a circular black disc to read the meridian in which the arc in shape of a semicircle with radius 330 mm. Its rotating in any direction and fix at any position with a tightening screw. 

The arc is graduated from 0º to 90º with a movable test object which is a white color spot of size 10mm diameter painted on a circular disc it can be moved with arc. An adjustable chin rest and a detachable leveling bar is fixed in front of the metallic arc. A scale and circular chart frame to hold the chart paper in position is provided at the back of the circular disc.