General information

Question text: How long does each episode of the darkening or graying out of vision last?
Answer type: Radio buttons
Answer options: 1 Few seconds
2 A few minutes
3 Ten to 60 minutes
4 A few hours
5 Longer than 24 hours
6 I don't know
Label: how long each episode of darkening or graying out of vision last
Empty allowed: One-time warning
Error allowed: Not allowed
Multiple instances: No

Data information

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