I was handed an older pair of sv surgery glasses with loops attached to the bridge and asked to make it into a pair of lined bifocals. My question is concerning the PD/OC and seg measurements. These loops are set inwards slightly and flip down over the front of the glasses. If I dot the center of the back of the lenses like a bullseye, where the loops rest, it's going to be about 10 mm above where the ft28 line could comfortably start as to not be in the line of sight when looking through them. I don't want to induce prism or unwanted astigmatism. They also sit towards the bottom of the glasses, it's double bridge style of frame and my doctor has an rx with astigmatism and -3.00 with a +2.00 add.

1. Should I specify an OC height of this bullseye marking with the lab and a separate seg height? I know std OC is set 5 mm above FT28 typically. OR should I set the oc height instead of the center of the loops circle, but just above the bottom viewing rim instead, as I know most people don't like looking below their oc but are okay looking above on a sv pair typically. Or leave it alone and just specify seg and be done with it.

2. Should I measure and use the pd from the pen markings of the center of each bullseye or use a normal far pd? Would this produce possible errors in decentration if i used the far pd? I don't have the near pd on file.

Any guidance would be greatly appreciated!