What Causes Eye Flashes In The Vision?

I have been experiencing a bright corona in my eye, especially in the morning and with head movement. It turns everything I look at a kind of bluish color, like looking through the afterimage of a flashbulb, but it lasts several minutes. I am on several medications and wonder if it could be a side effect. I do get migraines, but this is not typical for me. It's been happening more since I started on blood thinners. I have an appt with my ophthamologist (sorry I don't know how to spell that) in a month, but I'm wondering if I need to do that sooner. I am diabetic and have high cholesterol and arthritis...