cwatt1 is likely correct. The flashes however every once in a while represent traction on the peripheral retina so you should go back to your surgeon for a dilated eye exam to make sure the retina is fine.
It is probably your eye preceiving the edge of the IOL -- possibly the IOL is just slightly decentered. My understanding is that in the majority of cases these types of visual effects tend to lessen or go away over time, but it's hard to say how much time, or if they will disappear entirely.. If it is really bothering you, I'd ask your eye surgeon about it.
I had this exact thing happen to me after my cataract surgery. It was like a jiggling shake especially bad when I read. It only lasted a few weeks. I had already had a retinal detachment so it made sense that the surgery had irritated the retina and was causing some traction and flashes of light. That also calmed down quickly. I would see your doctor again if it's been five weeks and still having symptoms.