Flashes and floaters are most commonly experienced when the vitreous gel separates from the retina. This separation of the vitreous from the retina is called a Posterior Vitreous Detachment or PVD.
A PVD is a normal part of the aging process, usually occurring between the ages of 60 and 80. Separation of the vitreous can be seen at a younger age in nearsighted patients, or those with a history of inflammation, surgery or trauma to the eye. Most people who experience a PVD are suddenly aware of new floaters. Floaters are caused by the now contracted and separated vitreous floating visibly in front of the retina. These floaters are often quite large, and unlike floaters that the patient may have previously experienced. People often describe them as being like cobwebs, small flies, or a smudge in the vision which moves about. In addition to new floaters, some patients experience flashing lights as a symptom of PVD. Flashing lights occur due to the vitreous pulling on the retina. Flashes are typically described as sparks or split second arc-like flashes off in the peripheral vision. The flashing typically decreases over the first several weeks after the vitreous separation. Some patients have flashing lights without new floaters. Most people over time adapt to new floaters but it is possible to surgically remove them in severe cases.
If you experience new flashes or floaters, contact your eye doctor. In some cases, flashes and floaters may be caused by a retinal tear, and not a simple PVD. A retinal tear is a much more serious condition, often requiring laser treatment.