2018 Prisms
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Lecture for May 5, 2018, UP-PGH Sentro Oftalmologico Jose Rizal. Basic Course in Diagnostics and Instrumentation.
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2018 Prisms
- 3. Factors Affecting Measurement • Prism placement: – plastic prisms: frontal plane – glass prisms: prentice position • Stacking prisms • Splitting prisms From Rosenbaum & Santiago, Clinical Strabismus Management
- 4. Glass Prisms • One face perpendicular to light rays • Back face parallel to iris • Prisms in spectacles • Measure back surface of spectacles flat against nose cone of lensmeter
- 6. Inserting Prisms in Glasses • 1D lens, decentered 1 cm = 1 PD • Effectively only about 4 cm/4PD can be done by displacing center (beyond 5 cm already beyond edge) • Grind in beyond 4PD each lens(?)
- 10. Cover Tests and Endpoints • Cover Uncover Test • Simultaneous prism cover test • Prism under cover test • Alternate prism cover tests • Phorias, fixation preference • Monofixation • DVD • Gold standard for any misalignment
- 11. Skills Checklist • Differentiate between glass and plastic prisms • Prentice vs Frontal plane • Direction of prisms for ET, XT, HT/HoT • Stacking prisms • Splitting prisms • True vertical vs DVD • End point of prism testing • Neutralizing combined deviations: – XT w HoT in 3rd nerve – ET with DVD – XT with HT