Flashes refer to seeing light or bright shapes in the field of vision. They are likened to lightning streaks or camera flashes, usually in the outer part of your vision. They are visible with the eyes closed, and are more visible in the dark.
Floaters are dark dots, circles, strings or haze that drift around in the field of vision. They are more noticeable when you look at a white wall or the blue sky, and they move when you shift your gaze.
Flashes and floaters are mostly caused by the separation of the vitreous gel from the retina. However, it can also be a sign that the retina has been torn, and other conditions (e.g., inflammation, tumours, stroke) can also cause similar symptoms. A thorough examination by an ophthalmologist or optometrist is therefore recommended.
What Causes Flashes and Floaters?
A. The eye cavity is filled with vitreous gel, which contains invisible fibres. When you are younger, the vitreous gel is clear and is stuck onto the surface of the retina. As you get older, the fibres in the vitreous clump together and become visible as floaters. These long-standing floaters can be bothersome but they are harmless.
B. With aging, the vitreous becomes watery and shrinks in size, and it separates away from the retina. As the vitreous separates, it can pull on parts of the retina, which you may notice as flashes.
C. If there are weakened areas in the retina or the vitreous is abnormally stuck down, the pulling of the vitreous can lead to a tear or break in the retina. The symptoms of retinal tear are no different to the flashes or floaters from vitreous separation, so a careful examination is needed.
D. If not treated, a retinal tear can allow fluid to get under the retina and cause it to detach. Retinal detachment causes total blindness and must be treated by surgery.