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William Benevento, MD

simulation of floatersHave you seen small specks, blobs, lines or cobwebs swimming around in your vision? Or flashing lights that look like fireworks in your side vision? Flashes and floaters are very common as we age. So what causes them, and when should you be concerned?

What causes flashes and floaters?

Flashes and floaters are usually caused by something called a posterior vitreal detachment. This happens to almost everyone between the ages of 40 and 80. It’s when the jelly that fills the back of the eye, the vitreous, shrinks and peels away from the back of the eye, getting replaced by some fluid. As the jelly peels away, it can tug on the light sensitive layer, the retina, and tickle it, causing flashes that usually last just for a couple of seconds. Floaters happen when there are little densities on the back face of the jelly. These swish around in your vision and can look like cobwebs, a bunch of specks, or blobs floating around. Frequently, you see them when you look at a bland background like the sky.

Are these dangerous?

Not usually. For most people, the jelly separates from the light sensitive layer easily and nothing happens. But sometimes there’s a sticky spot between the jelly and the light sensitive layer, the retina, and as the jelly peels away from it, it tugs so hard that it can tear it. If this happens, then fluid can get behind the light sensitive layer and blister it off the back of the eye. This is called a retinal detachment, and you really don’t want to have one because it takes surgery to fix it. But if you get a tear and we catch it early, we can laser around the tear and weld it down, keeping the fluid from getting behind it. So if you get a bunch of flashing lights, a shower of a million little floaters, or a dark black curtain coming into your side vision, you need call us. It’s much better to catch a tear early, so we can laser it and prevent a detachment. But again, most folks don’t get tears.

Do the flashes and floaters go away?

Frequently, the flashing lights go away with time, especially as the jelly fully peels away from the back of the eye. You might still get a flash every so often, especially in a dark room, like when you get up in the middle of the night to go to the bathroom. You move your eye and the jelly bangs up against the retina, causing a flash. The floaters really never go away, but they may sink to the bottom of the eye or come further forward and out of focus. Even if they don’t, the brain is pretty good at ignoring things that don’t matter, and they become less noticeable with time.

Are there other things that cause flashing lights?

Some folks have flashing lights with their migraines. In fact, some folks just have the visual symptoms of a migraine without the headache at all. These are called ocular migraines or acephalgic migraines, literally “migraine without the head”. These look like heat waves or looking through water. Some look like looking through a kaleidoscope. The kicker here is that they last longer, say 15-45 minutes, and are frequently in both eyes. These are pretty common and are frequently confused with flashes and floaters, but have nothing to do with retinal tears.

Again, if you notice a bunch of flashing lights, a shower of a million little floaters, or a dark black curtain coming into your side vision, you should call us immediately. It’s usually not a big deal, but if it is a new tear, an ounce of prevention is worth a pound of cure.

Bio: Dr. Benevento is a board certified ophthalmologist. He practices at our office in Bettendorf, Iowa. For more information, please see our website:

The material contained in this article is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care provider.

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