Flashing lights are a common problem after cataract surgery, but often times it is caused by the aging process, not the cataract surgery.
In the back of the eye is a gel-like substance called the vitreous. It keeps the retina attached to the back wall of the eye and helps the eye maintain its shape. But as we get older, the vitreous liquifies and breaks up and eventually starts to detach from the retina. This is completely normal and happens to just about everyone, regardless of surgical status.
As the vitreous detaches from the retina, it can tug on it. Because the retina is essentially a sheet of neurons like brain tissue, it registers this pulling as a flash of light. Because the pulling typically takes place in the periphery of the retina, it looks like the flashes are taking place off to the side of your vision.
You may also notice black floaty things or clear, floating squiggles in your vision along with the flashes because as the vitreous liquifies, it also breaks up into small pieces that continue to float around in the eye.
Again this is completely normal, but if you notice that these flashes are becoming more frequent, you are noticing more floaters, or you see a veil or curtain coming over your vision, call your ophthalmologist right away and schedule an appointment for a dilated exam.