Serum cobalamin and folate in the optic neuropathy associated with tobacco smoking.

The concentrations of vitamin B12 in the sera from 77 patients diagnosed as suffering from the toxic optic neuropathy associated with tobacco smoking were compared with control levels and with serum folic acid concentrations from the same patients. Of these, 17 patients had associated pernicious anaemia. Serum vitamin B12 levels were significantly lower, whereas the folic acid concentrations showed great variation. Folic acid levels in the serum tended to be high when the vitamin B12 level was low (r = 0.29). The results suggest that the role of folic acid in the genesis of the optic neuropathy is not marked. However persistently low levels of folic acid occurred in one subject and significant clinical improvement resulted only from specific therapy.