Prism on Stick 35 PDStick Mounted Square Prismssold individually with your choice of values from 1 2 PD to 50 PD. Use Please Choose to select the Diopter desired. Stick mounted prisms stay cleaner and avoid as many fingerprints compared to square prisms. The less often they need to be cleaned, the longer they will last. Sticks are Stainless Steel. These high quality prisms are used to measure the deviation in strabismus. Prisms provide an efficient means for treating