C

Ethambutol is well-known for dose-related retrobulbar/toxic optic neuropathy, with vision loss and color-vision defects that improve on stopping the drug; this complication is documented in multiple case series and reviews [Shah et al., 2022, PMID 35638034]. The other listed drugs may cause different ocular effects (e.g., chloroquine—maculopathy) but are not classic causes of toxic optic neuropathy.