it works for all bifocals, even round segs.
remember, bifocals are basically a smaller lens fused into a larger lens.
In a -2.00 DS OU, +2.00 add
yes the total power in the segment is Plano, but you are not placing the segment oc directly in front of the eye.
Also,
Just because the total power is Plano in the segment, does not mean you cannot acheive prism.
A perfect example is the clip example I used above.
or how about this,
if you put on -2.00 sph contacts, then put on a pair of +2.00 readers.
would you need to take a PD measurement?
Or does PD not matter?
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