Spects for Thick Lenses
Relatively sturdy frames for:
A. Either Spherical or Cylindrical Lenses
More than + or - 3.0 D SPH
More than + or - 3.0 D CYL
B. Compound Lenses (Spherical & Cylindrical)
3.5 D or More
(Take bigger power among Spherical and Cylindrical Powers; + or - doesn't matter)
i.e. +3 SPH - 4 CYL will be 4 D though mathematically +3 is more than - 4