title: A bitoric rigid contact lens with base down prism to eliminate binocular vertical diplopia.
abstract: Prism base down can be incorporated into a rigid gas permeable contact lens to align the diplopic images in a patient who has a significant vertical phoria. A rigid lens may also incorporate both vertical base down prism and a toroidal back surface - the vertical prism to correct the heterophoria and the toric back surface to improve the physical fit of the lens on a highly toric cornea. This paper presents a case where vertical diplopia due to a post-surgical left hyperphoria of about four prism dioptres was eliminated by the incorporation of the appropriate amount of base down vertical prism into a bitoric rigid gas permeable contact lens.
authors.affiliation: Department of Optometry and Vision Sciences, The University of Melbourne, Australia.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Lindsay
authors.forename: Gerard W
authors.initials: GW
authors.lastname: Crock
mesh_terms: D003261:Contact Lenses; D019781:Corneal Topography; D004172:Diplopia / Q000209:etiology / Q000628:therapy*; D005260:Female; D006801:Humans; D008875:Middle Aged; D055095:Optics and Photonics; D013285:Strabismus / Q000150:complications / Q000628:therapy*; D016896:Treatment Outcome; D014792:Visual Acuity