Prismatic Effects in Bicentric Grinding

Résumé

Bicentric grinding is widely used to neutralize a vertical differential pris­matic effect at the near visual point. However, the prismatic effects in other portions of the reading field dif­fer from those at the near visual point. In this study, the variations in prismatic effect throughout the entire reading field are demonstrated. It is shown that a slab-off prism is most effective in spherical anisometropic prescriptions and when the differen­tial prismatic effects are symmetrical about the horizontal meridian.