The symptom of floaters in the eye is most often due to the separation of the posterior vitreous from the optic nerve. This is essentially a natural process that occurs in everyone. Once the vitreous, which has the consistency of uncooked egg white, separates, it condensates and thickens. This thickening process may result in a dense structure that casts a shadow onto the back of the eye. This what one sees are not protein particles, but rather their shadow. This explains why one cannot look at the floaters when trying to see them , as they a dart and bob about.
Flashes on the other hand, are misinterpreted electro chemical signals sent to the brain. That is, normally when light strikes the retina it stimulates a signal in the photoreceptors that is sent to the brian for analysis. However, during a vitreous detachment, the vitreous is mechanically pulling on the retina until it completely separates (or detaches). The mechanical pulling triggers the photoreceptors to fire off signals to the brain. The brain, not knowing taht the origin was mechanical , instead misinterprets the signal as a flash of light.
Other sources of light flashes are retinal detachments and ophthalmic migraines. The latter differs from vitreous flashes in that the flashes are usually not lightening bolt-like in only the affected eye, but instead are arc-like and occur in both eyes, lasting for a 15 to 30 minute period. Also, in the case of migraines, often the flashes are followed by a headache.
