Help!! visual disturbances 15 weeks

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I'm having random bouts of "partial blindness" that last anywhere from 30 minutes to an hour. It's like the center of my vision is a kaleidoscope while I can still see thing normal around it. Has anyone else experienced this? What is this??  15 weeks pregnant..
Edit: reading that this could be an ocular migraine? Should I be concerned about them? I've had 2-3 of them so far. And I had one last year.