Many people, at some time in their lives, notice floaters in one or both eyes. These are perceived as small spots or strands that seem to drift in the field of vision, traveling rapidly with eye movements and then floating slowly when eye movements cease. Floaters are most readily seen against a bright background such as well illuminated reading material, a computer screen, or bright sky.
Light flashes may occur in conjunction with floaters or may occur separately. Unlike floaters, light flashes (photopsias) are typically perceived in subdued lighting or even total darkness. Photopsias can range from minimal light twinkles to flashes that are bright enough to suggest a neon sign or camera flash.
What causes floaters and light flashes?
Most occurrences of floaters or light flashes relate to changes in the jelly-like substance called vitreous which fills the entire back cavity of the eye. The vitreous is transparent and has a solid consistency similar to gelatin. As people grow older, the vitreous undergoes a normal aging process, becoming more liquid and less jelly-like. Often the partially liquefied vitreous will abruptly “collapse” inside the eye causing a shower of floaters to appear. The floaters are aggregates of protein which have formed in the vitreous during the liquefaction process.
When the vitreous collapses, it begins to separate from the retina. The mechanical pull of the vitreous on the retina during this separation causes light flashes. Sometimes during this separation process a retinal tear develops and can lead to a retinal detachment. Often when a retinal tear occurs, at least a small amount of bleeding is present in the vitreous and may be noted by the patient as a multitude of black dots or a hazy decrease in vision.
Know the warning signs
The sudden occurrence of floaters or flashes can be an important warning signal of impending retinal problems. A small percentage of people who develop the abrupt onset of prominent floaters or light flashes in an eye will be found to have a retinal tear on careful ophthalmoscopic examination. Retinal tears can often be treated with laser or freezing methods if a beginning retinal detachment is not present.
Fortunately, the majority of people who experience floaters or light flashes do not develop serious retinal problems. In most instances, the floaters and flashes gradually subside over a period of time with no permanent alteration in vision. Since flashes and floaters can, however, be an important warning of a retinal tear or impending retinal detachment, their sudden appearance is of sufficient concern to warrant careful evaluation by your ophthalmologist.