Originally posted by rhodopsin Eclipse is reagent grade methanol. Eclipse 2 is the same with a little distilled water to slow evaporation. Other lens cleaning fluids contain highly diluted ammonia; I don't know diluted with what, but assume distilled water. Naptha also works well. Acetone has been used, however besides being highly toxic, it also readily melts paints and plastics -- better to use on loose elements than mounted, but not on a cemented lens group.
A gentle approach using increasingly harsh substances is recommended, stopping when results are sufficient. When use of liquids stage is reached, spot clean rather than wiping the entire surface. Unused clean-room grade microfiber cloths and lint-free q-tips. Begin with blower, then a brush, then methanol or ammonia, then naptha, then disassemble and use acetone as last resort.
Where did you get this information concerning toxicity of acetone? When I investigated this I determined otherwise. Now solvents like toluene are really toxic, lacquer thinner, contact cement thinner, many other solvents, but acetone IIRC is fairly benign. I wouldn't drink it, of course. It is an excellent solvent for many things, but it does attack a lot of plastics and I'd think that lens coatings may suffer damage if in contact with acetone. BTW, I believe that common nail polish remover is acetone.