The chances are that the small lenses are cast from a monomer. The most commonly used monomer for ophthalmic lenses is CR39 (CR stands for Columbia Resin), this yields a cast lens with a 1.498 refractive index.
If you use a CNC machine to cut the lenses you'll need to have a means of polishing them. The most common polishing agent these days seems to be aluminium oxide, sometimes additives are added to improve lubrication during the polishing process. Lenses that have been cut on a CNC usually go through a two stage polishing process, the first process is called 'fining' and this smooths the lens to a dull polish using an abrasive 'fining pad'. The next stage involves using a felt pad and a slurry of polishing compound, this needs to be chilled to prevent overheating.
You'll need some fining and polishing 'tools' of the correct curvatures for the surfaces of the lenses you're wanting to polish. You'll also need to work out the curvatures of the front and back surfaces of the lenses taking into account the amount of material that will be removed in the fining and polishing processes. Otherwise you'll end up with lenses that are either too weak or too strong.
As technology progresses there are now CNC mills available that are able to produce such a good surface directly off the mill that you only need to polish them and you can miss out the first fining process.
That's a fairly simplistic overview of lens production, I hope it's somewhat useful to give you an idea of what you're up against.
Cheers
Jem
Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001
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Originally Posted by chad
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