When checking the distance power of a progressive lens, which side should face the operator?

When checking the distance power of a progressive lens, the correct practice is to ensure that the convex side of the lens faces the operator. This allows for proper measurement of the lens’ power as it is structured for viewing through the front surface, which is convex.

In a progressive lens, the distance portion is located at the top of the lens, and it is essential to orient the lens with the convex side directed towards the operator to accurately assess the optical characteristics. The convex surface is the one that refracts light as it enters the lens, and thus it is the surface that determines the power that the wearer will experience for distance vision.

If the concave surface or other sides were faced towards the operator, it wouldn’t provide a true measurement of the distance power. The flat surface is not relevant in determining the power since it does not contribute to the lens prescription. Hence, facing the convex side to the operator is imperative for correct evaluation of the distance vision aspect of progressive lenses.