Does anyone wear high index bifocals?

Question

Can you tell me if making lens high index makes the bottom and top thinner, as well as the sides, or only the sides?

Answer 1

It makes the whole lens thinner that a non- hi index lens...but if there is an astigmatism correction , the axis will make a difference as to where the thickness will be also.

Within 40 degrees of 90 on either side, the thickness will be on the outer edge...but within 40 degrees either side of 180 , most of the thickness would be at top and bottom, and be cut off when the lenses are cut for the frame.

If there is just a sphere power, the thickness would be reduced evenly all over...IF the eyes are centered in the frame.

So, the frame size, decentration and cylinder axis all can make a difference.