At +18 D in cr39 choices are limited to +18 or higher base curve spherical segmented multifocal (Super Modular only goes up to about +16 BC I believe).
Lenticulation will allow a larger frame but make sure the "B" is sufficient to keep the power curve from being edged. Because it's spherical only, the off-axis optics will be poor, but not as bad as it would be with a low Abbe hi-index material or bi-convex I think.
Free-form can clean up the off-axis optics but working on a steep base blank may not be mechanically possible. Full-field will require, depending on the subject's IPD, an "A" of about 38mm to 42mm.
Measure both the refracted and wearing vertex. If N/A you might have to over-refract and remake. Price accordingly.
Hope this helps,
Robert Martellaro
https://aoloptical.com/lens-data/
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