Hi, Thanks for writing in. Chemotherapy for Neuromyelitis optica can have different responses in different patients and variable responses in the same patient under different circumstances. It looks like the chemotherapy is showing variable response in your case. The improvement and worsening of vision depends on the recovery of the optic nerves and the swelling around it. When chemotherapy is given then there can be some initial swelling of optic nerve sheath and this can cause temporary worsening of vision. This can then improve slowly with time as the chemotherapy response gets better. Therefore the initial worsening can be due to the swelling of the nerves and with continued treatment this will improve. However since vision is an important area therefore please discuss in detail with your doctor. Please do not worry.