Retinal detachment is a serious eye condition that almost always leads to blindness if not treated promptly.

The retina is the light-sensitive tissue that lies smoothly against the inside back wall of your eye. Underneath the retina is the choroid, a thin layer of blood vessels that supplies oxygen and nutrients to the retina. Retinal detachment occurs when the retina separates from this underlying layer of blood vessels. Unless the detached retina is surgically reattached, you may permanently lose your vision in the affected eye.

Signs and symptoms

Retinal detachment is painless, but visual symptoms almost always appear before it occurs. Warning signs of retinal detachment include:

• The sudden appearance of many floaters — small bits of debris in your field of vision that look like spots, hairs or strings and that appear to float before your eyes

• A sensation of flashing lights that usually occurs in one eye but can be present in both eyes at the same time

• A shadow over a portion of your visual field

• Blurred vision

Because most tears occur along the periphery of the retina, you may not initially notice blurring in your peripheral vision.

Causes

At the root of retinal detachment are changes to the jelly-like vitreous that fills the vitreous cavity of your eye. Over time your vitreous may change in consistency and partially liquefy. It may also begin to shrink. The partial liquefaction may progress to a point where the vitreous sags and separates from the surface of the retina. This is called posterior vitreous detachment (PVD), or vitreous collapse. It's a common condition and occurs to some extent in most people's eyes as they age.

PVD usually doesn't cause serious problems. The shifting or sagging vitreous may cause the appearance of new or different floaters in your field of vision. What look like spots, specks, hairs and strings are actually small clumps of gel, fibers and cells floating in the vitreous. And what you're seeing are the shadows that this material casts on the retina. Common floaters appear gradually over time and, although they're annoying, they are rarely a problem. They hardly ever require treatment.

If the vitreous pulls on the retina as it shifts and sags, you may see flashes of sparkling lights (photopsia) when your eyes are closed or when you're in a darkened room. The phenomenon lasts for only a few seconds.

However, floaters and flashes can signal a more serious eye problem, particularly if they appear suddenly and with great intensity. When the pull of a sagging vitreous is strong enough, the retina may tear, leaving what looks like a small, jagged flap in the retina. Most tears occur along the periphery of the retina. That's where the vitreous is more firmly attached and can't separate without tugging hard. Such tears can lead to retinal detachment.

Retinal detachment occurs when vitreous liquid starts to leak underneath the retina at places opened by the tears. Leakage can also occur at tiny holes where the retina has thinned due to aging or other retinal disorders. As liquid collects, the areas of the retina surrounding these defects may begin to peel away from the underlying layer, the choroid. Over time these detached areas may expand, like wallpaper that, once torn, slowly peels off a wall. The areas where the retina is detached lose their ability to see.

Not all tears and holes in the retina lead to retinal detachment. Sometimes the retina in the area of these defects remains relatively well attached to the choroid. But detachment that goes undetected and untreated can progress and eventually involve the entire retina with complete loss of vision.

Risk factors

Your risk of developing a detached retina generally increases with age simply because the vitreous changes as you grow older. You're also at greater risk if you have had a previous retinal detachment in one eye or a family history of retinal detachment or are:

• Nearsighted

• Male

• White

The following factors can cause the vitreous to pull at and tear the retina, so they also increase your risk of retinal detachment:

• Previous eye surgery

• Previous severe eye injury

• Weak areas in the periphery of your retina