Seeing occasional black spots is quite normal. Many people experience them throughout their lives. Sometimes, though, it is a sign of a potentially dangerous condition. When you see a flurry of black spots, it could mean that your retina is about to detach from the back of your eye. If you see a lot of black spots, you must seek medical care immediately.
The black spots you see are called floaters. According to the National Eye Institute, floaters can look like spots, strands or squiggly lines. The spots move around slowly if you stop moving your eyes. If you try to focus on them, they move quickly out of the way. You can see them more easily if you look at something that is all white or the sky.
A retinal detachment is when any part of the retina detaches from the back of the eye. With any degree of detachment, you will suddenly see many black spots along with light flashes. This is considered an eye emergency--it can lead to blindness if not treated, or your peripheral vision may be impaired for life. You must treat it within two or three days.
Floaters, or black spots, are simply a sign of ageing. The little specks are shadows cast by strands of the vitreous, the gel-like filling that keeps your eye round. The vitreous shrinks over time, becoming stringy in the process. These strings start to cast shadows that you see as black spots. At first, these spots may be very apparent, but they tend to settle below your line of sight. Most people learn to ignore them.
Although for most people it is a natural occurrence, for others it could signal infection, hemorrhaging, inflammation, eye injury or retinal tears. If you suddenly start to see a lot of floaters, get your eyes checked out by your doctor.
If the black spots you see are so dense they affect your vision a vitrectomy can be performed, which will remove the vitreous and replace it with a salt solution, This surgery is not without risk--it can lead to complications such as retinal detachment and cataracts. It is resorted to only if the black spots actually prevent you from seeing clearly. If the floaters are simply the result of ageing, then no treatment is needed or recommended.
According to the American Diabetes Association, to decrease your chances of eye problems have your blood glucose levels checked, keep your blood pressure within range, quit smoking and get an annual dilated eye exam. If you start to see many spots and possibly flashes of light, see a doctor as soon as you can.