American Board of Opticianry (ABO) Practice Test 2025 - Free ABO Practice Questions and Study Guide

Question: 1 / 400

Which combination of prism is not a canceling situation?

Base In and Base In

Base Out and Base Out

Base Up and Base Up

The correct choice indicates a combination of prism that creates a non-canceling situation. When two prisms are oriented with their bases aligned in the same direction, they reinforce one another rather than canceling out their effects.

In the case of Base Up and Base Up, both prisms direct light in an upward direction, contributing to an overall upward displacement of vision rather than negating each other. This means that the resultant effect is an increase in the perceived displacement in the vertical plane, making it important in the context of treatments for conditions that may benefit from vertical (upward) prism application.

Understanding how prisms interact is crucial for opticians, especially when considering adjustments for patients with binocular vision issues. In contrast, combinations where the bases align against each other, like Base In with Base Out, would tend to negate the effect of each other.

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Base Out and Base Out

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