From which component do you read the smaller prism component when checking prism?

• A. Reticle scale inside the instrument
• B. External prism compensating device
• C. Frame hinge
• D. Pupil distance ruler

Answer: (A)

When checking prism, the precise, smaller prism component is read from the reticle scale inside the instrument. This internal reticle is calibrated to show fine increments of prism diopters, allowing you to read fractional or small additional amounts that aren’t captured by the larger external prism settings. The external prism compensating device is used to offset overall prism power, not to provide the fine readout. The frame hinge and the pupil distance ruler aren’t involved in reading prism values. So, to determine the exact small prism component, you look at the reticle scale inside the instrument.