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However , we recently saw two patients with renal tuberculosis treated with ethambutol in whom visual loss from toxic optic neuropathies was severe and irreversible despite careful ophthalmological monitoring and prompt discontinuation of the agent at the first sign of impaired visual function .
 adverse effect: toxic optic neuropathies, ethambutol; adverse effect: visual loss, ethambutol
Given a phrase that describes the relationship between two words, extract the words and the lexical relationship between them. The output format should be "relation1: word1, word2; relation2: word3, word4". 
Option: adverse effect 
Text: {0} 
Answer:
 adverse effect: toxic optic neuropathies, ethambutol; adverse effect: visual loss, ethambutol