When checking the near power of a front surface progressive lens, which side should face the operator?

When checking the near power of a front surface progressive lens, the concave side should face the operator. The concave side is where the lens' power is measured for near vision. In a progressive lens, the design varies in power across the surface, transitioning from distance vision at the top to near vision at the bottom.

For accurate measurement, positioning the concave side towards the operator allows them to assess the near power effectively. Additionally, the progressive design features a gradient of powers, and measuring from this side ensures that the operator can clearly detect the intended prescription needed for reading and other near tasks. This placement is essential because observing the lens from the wrong side could lead to misreading the powers, potentially causing fitting errors in the final product.