ABO Exam Practice Test – Free Study Guide & Optician Test Prep (2025)

Minus lenses are typically viewed in terms of prisms as apex to apex. This means that the direction of the prismatic effect is from the apex (top) of the lens to the apex (top) of the prism base. The other options are incorrect because they do not specify the directionality of the prismatic effect and may cause confusion. For example, base to base could refer to placing the base of the prism against the base of the lens, or placing the base of the lens against the base of the prism. Similarly, base to apex and apex to base could be interpreted in multiple ways. Therefore, apex to apex is the most clear and standard way to refer to the direction of prismatic effect when using minus lenses.