[However, a sudden increase in floaters, possibly accompanied by light flashes or peripheral (side) vision loss, could indicate a retinal detachment. A retinal detachment occurs when any part of the retina, the eye’s light-sensitive tissue, is lifted or pulled from its normal position at the back wall of the eye.

A retinal detachment is a serious condition and should always be considered an emergency. If left untreated, it can lead to permanent visual impairment within two or three days or even blindness in the eye.

Those who experience a sudden increase in floaters, flashes of light in peripheral vision, or a loss of peripheral vision should have an eye care professional examine their eyes as soon as possible.]
https://www.nei.nih.gov/health/floaters/floaters