Many people notice floaters in one or both eyes at some point in their lives. These are perceived as small spots or strands that seem to drift into the field of gaze, traveling rapidly with eye movements and then floating slowly when eye movements cease. Floaters are most readily seen against backgrounds such as well-illuminated reading material.
Light flashes may be seen in conjunction with floaters or may occur separately. Unlike floaters, light flashes (photopsias) are typically perceived in subdued lighting or even in total darkness. Photopsias range from minimal light twinkles to flashes that are bright enough to suggest a neon sign or camera flash.
Most occurrences of floaters or light flashes relate to changes in the jelly-like substance called vitreous which fills approximately 80% percent of the eye. The vitreous is transparent and has a solid consistency similar to gelatin. As we grow older, the vitreous undergoes a normal aging process and becomes more liquid and less jelly-like. Often the partially liquefied vitreous will abruptly “collapse” inside the eye, causing a shower of floaters to appear. These floaters are aggregates of protein that have formed in the vitreous during the liquefaction process. When the vitreous collapses, it separates 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 may occur which can let fluid leak under the retina, causing a retinal detachment. Often when a retinal tear occurs, at least a small amount of blood is present in the vitreous and may be noted by the patient as a multitude of very small floaters and hazy decrease in vision.
The sudden onset of flashes or floaters can be an important warning signal of impeding problems. Approximately one in every ten people who have an abrupt onset of prominent floaters or light flashes will be found to have a retinal tear upon careful ophthalmoscopic examination. Retinal tears can often be treated with laser or freezing methods if a beginning retinal detachment is not present.
Most people who experience floaters or flashes of light do not develop severe retinal problems. In most cases, the floaters and flashes gradually subside over a period of time with no permanent change in vision. Since flashes and floaters can be an important warning of a retinal tear or impending retinal detachment, their appearance is of sufficient concern to warrant careful evaluation by your ophthalmologist.