What besides a retinal tear would cause bright flashes of light in the corners of the eyes?

Photopsias: These are termed photopsias. They are due to jiggling of the retina by the internal components of the back of the eye. Most common is due to changes in the vitreous fluids which stimulate the retina without knocking it loose. Since retinal detachment is always a possiblity with this symptom, check with your ophthalmologist to rule out this diagnosis.

See below: Floaters, flashing lights, or part of the peripheral vision missing (like a curtain or veil obscuring your vision) indicates the need for an urgent dilated retinal examination to rule out retinal tear or detachment. It could also be an ocular migraine, posterior vitreous detachment, retinitis, or tumor. Get it checked.