Floaters and Flashes: The Vitreous and the Retina

Floaters and flashes are among the most common visual symptoms, and both are usually related to the vitreous, the clear gel that fills the back of the eye. With age the vitreous liquefies and eventually separates from the retina in a process called posterior vitreous detachment. Clumps of collagen in the gel cast shadows on the retina that are seen as floaters, while traction of the gel on the retina stimulates the photoreceptors mechanically and is perceived as brief flashes of light, usually at the edge of vision.

In most people the process is harmless. In a minority, however, the separating vitreous tears the retina, and fluid passing through the tear can lead to retinal detachment, which causes a spreading shadow or curtain in the visual field. For this reason clinical guidance treats the sudden onset of floaters and flashes as a reason for prompt dilated examination of the retina.

Retinal tears found before detachment can often be sealed with laser or cryotherapy in the clinic..