NGF and neurofibromatosis type 1: A study of 51 patients with NF1 showed that whilst only 8% had abnormal nerve conduction, thermal thresholds were abnormal in 13%, IENFD was reduced in 22%, and corneal NFL was pathologically reduced in 52%.2 Another recent study has also shown that patients with NF1 have decreased corneal sensitivity and increased corneal nerve branching but with no changes in tear levels of nerve growth factor or brain-derived neurotrophic factor levels.17