PURPOSE: This is to study the progressive addition lens (PAL) under the physiological optics’ view, to show the lensometer findings and its applicability to daily work. METHODS: At first, the aa., explains the ways to examine the PAL , and then indicates the physical basis applied to study the prismatic system of the concave and convex lens. It then examines the differences on progression zone extension and explains its diagonal position. Thirteen pairs of lenses from the same manufacturer were […]