If you have ever noticed a few tiny dots, blobs, squiggly lines or cobweblike images drifting across your field of vision, you are not alone. These visual disturbances, called floaters, are common, and most people simply dismiss them as a normal part of growing older. But that's not always the case.

When it could be serious: In about 15% of cases, floaters are a symptom of a harmful condition known as a retinal tear, which can, in turn, lead to a vision-robbing retinal detachment in a matter of hours to days.

How does this happen?

The retina, which is an extremely thin, delicate membrane that lines the inside of the back of the eye, converts light into signals that your brain recognizes as images. However, with age, a jelly-like material called the vitreous that fills much of the eyeball commonly shrinks a bit and separates from the retina. If the shrinkage or some other injury exerts enough force, the retina can actually tear.

You might notice a sudden shower of new floaters or flashes of light that look like shooting stars or lightning bolts. What you're seeing when this occurs are actually shadows that are being cast on the retina by the tiny clumps of collagen fibers that comprise the floaters. The flashes of light are caused by the tugging of the vitreous on the retina, which stimulates the photoreceptors that sense light.

Why floaters and/or flashes are a red flag: The retina lacks nerves that signal pain, so these visual disturbances are the only way you will be alerted to a tear. Left untreated, fluid can leak through the retinal tear, and the retina can detach like wallpaper peeling off a wall. A retinal detachment is an emergency-if it's not treated promptly, it can lead to a complete loss of vision in the affected eye.

Are you at risk?

Changes in the eye that increase risk for a retinal tear or detachment begin primarily in your 50s and 60s-and continue to increase as you grow older.

In addition to age, you can also be at increased risk for a retinal tear or detachment due to...

Nearsightedness. People of any age with nearsightedness greater than six diopters (requiring eyeglasses or contact lenses with a vision correction of more than minus six) are five to six times more likely to develop a retinal tear or detachment. That's because nearsighted eyeballs are larger than normal. Therefore, the retina is spread thinner, making it more prone to tearing.

Important: If you're nearsighted, don't assume that corrective eyewear or LASIK surgery decreases your risk for a retinal tear or detachment. Neither does.

Cataract surgery. This surgery alters the vitreous jelly, increasing the risk that the vitreous will pull away from the retina, possibly giving way to a retinal detachment.

Cataract surgery has been known to double one's detachment risk, but a new Australian study suggests that improvements in technology, such as phacoemulsification, which uses an ultrasonic device to break up and remove the cloudy lens, have cut the risk from one in 100 to one in 400.

Diabetes. Because it impairs circulation to the retina over time, diabetes leads to a higher risk for a severe type of retinal detachment that is not associated with floaters and flashes and can be initially asymptomatic.

Individuals who have diabetes should be sure to have annual eye exams with dilation of the pupils to check for this and other ocular complications of diabetes. The Optomap test provides a wide view of the retina, but you also need pupil dilation for a thorough screening.

The Danger of a Retinal Tear

Anyone who experiences a sudden burst of floaters or flashes, especially if they are large or appear in any way different from how they have in the past, should contact an ophthalmologist right away for advice.

If an eye exam confirms a retinal tear, it can be treated in an eye doctor's office, using either lasers or freezing equipment to "spotweld" the area surrounding the tear. (Anesthetic eyedrops are used to numb the eye, but the procedure can still be uncomfortable.)

The resulting scar tissue will seal off the tear so the fluid doesn't leak behind the retina and pull it away. The good news is that both laser photocoagulation and. freezing are more than 90% effective in preventing detachment. There is a small risk for tiny blind spots.

When a detachment occurs

If you suffer a retinal tear but don't get treatment within a day or two, the fluid can seep through the tear, detaching the retina.

Red flag for detachment: A gradual shading in your vision, like a curtain being drawn on the sides or top or bottom of your eye, means that a retinal detachment may have occurred. If your central vision rapidly changes, this also may signal a retinal detachment or even a stroke.

Retinal detachment is an emergency! When your doctor examines you, he/she will be able to see whether the center of your retina is detached. When the center is involved, vision often cannot be fully restored.

If you have suffered a retinal detachment, your doctor will help you decide among the following treatments...

Vitrectomy. This one- to three-hour surgery is performed in a hospital operating room, usually with sedation anesthesia plus localized numbing of the eye. The vitreous is removed, tears are treated with lasers or freezing, and a bubble (typically gas) is injected to replace the missing gel and hold the retina in place until the spot-welding treatment can take effect. (The bubble will gradually disappear.)

Important: It is necessary to keep your head in the same position for seven to 14 days in order to "keep the bubble on the trouble," as doctors say. Therefore, you will need a week or two of bed rest at home. You may have to keep your head facedown or on one side.

Scleral buckle. With this procedure, a clear band of silicone is placed around the outside of the eyeball, where it acts like a belt, holding the retina against the wall of the eyeball.

Also performed in a hospital operating room, scleral buckle involves freezing the retina or treating it with a laser to create localized inflammation that forms a seal, securing the retina and keeping fluid out.

Scleral buckle takes from one to two hours and is sometimes combined with vitrectomy to improve the outcome. It is frequently used for younger patients and those who have not had cataract surgery.

Pneumatic retinopexy. Depending on where the retinal detachment is located, a 20-minute, in-office procedure called a pneumatic retinopexy is an option for patients with smaller tears. With this procedure, a gas bubble is injected, and retinal tears are frozen or treated with a laser.

This is followed by up to two weeks of bed rest. Your head may need to be held in a certain position, such as upright at an angle, depending on the location of your tear.

With pneumatic retinopexy, the reattachment success rate is lower than that of scleral buckle or vitrectomy (70% versus 90%), but it is less invasive and no hospital visit is required. In addition, pneumatic retinopexy costs less than a hospital-based procedure, which could range from $5,000 to $10,000.

Even with a successful procedure, 40% of patients who suffer retinal detachments see 20/50 or worse afterward even when using glasses. The remainder have better vision.

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