A transparent solid, with sides that converge at an angle, that deflects a ray of light toward the thickest portion (the base) and splits white light into its component colors; in spectacles, a p. corrects ocular muscle imbalance. [G. prisma]
- enamel prisms SYN: prismata adamantina, under prisma.
- Fresnel p. a p. composed of concentric annular rings.
- Nicol p. a p. that transmits only polarized light.
- Risley rotary p. a p. with a circular base that is rotated in a metal frame marked with a scale; used in examination of ocular muscle imbalance.
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pediatric risk of mortality; Platelet Receptor Inhibition in Ischemic Syndrome Management [study]

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prism 'priz-əm n
1) a polyhedron with two polygonal faces lying in parallel planes and with the other faces parallelograms
2) a transparent body that is bounded in part by two nonparallel plane faces and is used to refract or disperse a beam of light
3) a crystal form whose faces are parallel to one axis esp one whose faces are parallel to the vertical axis

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(prizґəm) [Gr. prisma] a solid of glass, plastic, or a similar substance with a triangular or polygonal cross section, which splits up a ray of light into its constituent colors and turns or deflects light rays toward its base. Prisms are used to correct deviations of the eyes, since they alter the apparent situation of objects. Abbreviated Pr.

Medical dictionary. 2011.