It does vary from manufacturer to manufacturer. However, there are quite a number of contacts available with strengths up to +20. The higher diopters are used a lot by aphakic people, but there aren't very many of 'em now since IOLs are pretty standard.
I guess that someone needing a +12 could wear a +10 contact lens with a +2 glasses lens over it. This combination would make the glasses lens much thinner and less magnifying to onlookers.
Thank you both for your replies...I'm curious, because I notice that myopia prescriptions can go very high, and hyperopia does not. What would happen if someone needed more than a +10 prescription?? By the way, this is not for me, I'm simply curious. Thanks
As Dr. Hagan stated, it varies by brand. For example, Proclear Compatibles are available in +10; Acuvue Oasys come in +8. Try going to the site of an online seller and checking out the availability of other brands. (Google "buy contacts online".)
varies from company to company.
JCH MD