What is the Major Reference Pupil (MRP)?

• A. The point on the lens where the patient's pupil is or where the visual axis passes
• B. The geometric center of the lens
• C. The optical center of the lens
• D. The frame's center

Answer: (A)

Major Reference Pupil is the point on the spectacle lens where the patient’s pupil sits, or the point where the eye’s visual axis passes through the lens. This point serves as the main reference for aligning the lens with the wearer’s line of sight in primary gaze, helping ensure the correct part of the lens is used and that unwanted prism effects from decentration are minimized. It is not simply the geometric center, nor the optical center, nor the frame’s center. Using the MRP ties the wearer’s pupil position to the lens geometry so eyewear is centered with how the person actually looks straight ahead.