671
RESULTS : All patients had optic neuropathy between 1 to 6 months ( mean = 2 . 9 months ) after starting ethambutol therapy at a dosage ranging from 13 to 20 mg / kg / day ( mean = 17 mg / kg / day ) .
 Disease: optic neuropathy; Chemical: ethambutol
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Disease: optic neuropathy; Chemical: ethambutol