What can doctors do about nearly blind eye?

It a depends. Depends on the cause. Some causes of blindness, cataract and corneal in particular, can be surgically repaired. Others may fall into a need to preserve what vision remains with treatment for glaucoma or retinal disease.
Almost blind. Depends on the cause of the near blindness. You must see your doctor to examine your eye to determine the cause and give you treatment to save your sight.