How is ethambutol toxicity treated?

My mother suffered ethambutol toxicity due to which 85% of her sight is lost. Is there any treatment or surgery to reduce the damage caused to her optic nerve?

 

Ethambutol toxicity may partially recover over a period of few months after stopping the drug and having a course of Vitamins B1, B6 and B 12. But if there is along time lapse things may not change now.