We report a case of rhinogenous optic neuritis in a 50-year-old man de
monstrating drastic diurnal variation in visual function. His left vis
ion was 20/15 in the morning, which gradually decreased to counting fi
ngers at night. Pupillary reaction and visual field showed the same fl
uctuation as vision. Complete remission of visual symptoms was achieve
d after endonasal ethmoid sinusotomy.