GULDEN VERTICAL PRISM BAR
11117 - BV-15 Prism BarSizes - 1-2-3-4-5-6-8-10-12-14-16- 18-20-25-30.Guldenﾒs plastic ophthalmic prism bars have been re-engineered to solve the problem of birefringence which can hinder their use in certain clinical applications. Our exclusive manufacturing process greatly reduces optical strain, producing prisms that virtually eliminate clinical birefringent effects. Prism birefringence can adversely affect your vectographic testing by degrading target contrast ("image washoutﾔ), or in extreme cases, by reversing the eye that sees the target (ﾓvectographic reversalﾔ). Birefringence occurs in ordinary prisms because of optical strain which is due to minute molecular misalignments that occur in plastic manufacturing.