American Board of Opticianry (ABO) Practice Test

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Prepare for the ABO (American Board of Opticianry) Test with interactive flashcards and hundreds of multiple choice questions. Updated for 2024 to help you excel on exam day

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Which combination of prism is not a canceling situation?

Base In and Base In
Base Out and Base Out
Base Up and Base Up
Base Out and Base Out

The correct answer is: Base Up and Base Up

The combination of Base Up and Base Up is considered not a canceling situation because both prisms direct light in the same direction, resulting in a cumulative effect rather than cancellation. When two prisms are oriented with their bases in the same direction, they reinforce each other, effectively increasing the total prismatic effect rather than neutralizing it. This leads to an increased deviation of light rays, which can exacerbate any existing visual conditions rather than alleviating them. In contrast, combinations where the prisms are oriented in opposite directions or serve to counteract each other's effects would create a canceling situation, effectively nullifying the prismatic influence on the visual pathway. Understanding these concepts is crucial for opticians to properly assess and prescribe prism in corrective lenses.