946
PATIENTS: Two patients, ages 40 and 51 years, undergoing treatment with interferon alfa for malignant neoplasms experienced sudden bilateral, sequential visual loss with disc-related field defects and segmental optic disc edema.
 adverse event: experienced 
Please tell me event type and its trigger word from given type options. Output format is "type: trigger".  Option: adverse event, potential therapeutic event 
Text: {0} 
Answer:
 adverse event: experienced 