"Specifically, I have one on my optic nerve. If marijuana can help, what type and/or concentration of CBD:THC should I be using?"
Whole plant cannabis can help shrink tumors. Specifically, medicinal acidic cannabinoids have been found to be the most potent at shrinking tumors. Check out this whole plant product that contains cannabis, turmeric, and ginger. It has over 527mg of raw acidic cannabinoids per bottle. https://evaonline.org/products/better-relief