Which type of lenses require an MRP height measurement?

The correct choice identifies polycarbonate and hi-index lenses as the types that require a minimum reference point (MRP) height measurement. MRP height is critical in fitting these lenses because they are often thinner and lighter than other materials and require precise positioning in relation to the wearer's pupil for optimal visual clarity and comfort.

Both polycarbonate and hi-index lenses provide significant advantages, such as increased impact resistance and lighter weight compared to traditional plastic. To ensure that these benefits are fully realized, accurate MRP height measurements are essential. This helps to avoid issues like visual distortions, particularly in high prescriptions or progressive lenses, ensuring that the optical centers of the lenses align properly with the wearer's eyes.

Other lens types, such as glass, acrylic, and conventional plastic, may not necessitate such precise measurements for effective fitting, as they generally have different physical properties or are used in simpler prescriptions where the variance in fitting might be less critical. Thus, polycarbonate and hi-index lenses stand out as requiring this careful measurement to maintain optimal optical performance.