If the optical center placement of eyewear is 2mm lower than the customer's line of sight, what type of prism has been induced in a plus power RX?

When the optical center of eyewear is positioned lower than the customer's line of sight, the design of the lenses creates a prismatic effect that directs light outward along the vertical axis. In this situation, it causes the light to bend downwards relative to the line of sight, which results in the optical effect known as base down prism.

Base down prism occurs when the base of the prism is oriented downward. This can happen if the optical center is misaligned vertically—specifically, if the center is lower than where the eye naturally looks. With plus power lenses, which are convex, this misalignment emphasizes the downward angle and directs the visual experience lower than intended. This results in the perception that is characteristic of base down prism, where objects appear higher than they are due to the lens effect.

The other types of prism listed would not apply in this context. Base up prism, for instance, would occur if the optical center were higher than the line of sight. Base in and base out prisms deal with lateral displacement of light and are relevant to horizontal misalignments, not vertical ones. Hence, the identification of base down prism in this scenario is accurate based on the principles of optics and geometry in lens design.