WARNING: Maybe Extreme Tech for your taste!
So, I just found a way to make contact lenses! Im not sure if this is the normal way they make them.
To fit the lenses, or to get better vision, you need to control the curvature of the lenses. And of course you need optical clarity.
Using PDMS solves the problem of optical clarity.
Now to control the curvature and hence the Power of the lens. Take a bottle of a small diameter. Now you can consider the bottle to act like a capillary. Pour some water in it. Because of the surface tension, a neat depression forms. Voila! Youve just got your self the basic mold for the lenses. Instead of water, pour PDMS and let it set. You just made the solid mold.Pour another thin layer of PDMS and then peel it ( there might be a glitch here, PDMS might bond with the older one).
How do I control the power, you might ask… So now, the curvature depends on the diameter of the bottle and the material of the wall. Choose them appropriately and you got yourself your home made lenses.