Oxygen transmission data? (contact lenses)

Hi:

Where can I find a comparison table that shows relative oxygen transmission
levels for various contact lenses? Either by brand or material. A website or
web page would be great.

It seems that more transmission is better, but how important is it?

I recently tried Silicone Hydrogel lenses, but had problems w. stinging. Am
looking at alternate brands/materials, and which do reasonably well
oxygen-wise.

thx!