Retinal Detachment
Medical Author: Andrew A. Dahl, MD, FACS
Medical Editor: Melissa Conrad Stöppler, MD
What is the retina?
The retina is an extremely thin tissue that lines the inside of the back of the eye. When we look around, light from the objects we are trying to see enters the eye. The light image is focused onto the retina by the cornea and the lens. This light striking the retina causes a complex biochemical change within layers of the retina and this, in turn, stimulates an electrical response in other layers of the retina. Nerve endings within the retina transmit these signals to the brain through the optic nerve. Within specific areas of the brain, this electrical energy is processed to allow us both to see and to understand what we are seeing. The retina has been compared to the film of a camera. However, film, once used, has a permanent image on it. The retina continually renews itself chemically and electrically, allowing us to see millions of different images every day without them being superimposed.
The retina is about the size of a postage stamp. It consists of a central area called the macula and a much larger peripheral retina. The light receptor cells within the retina are of two types, called the rods and the cones. Rods allow us to see in reduced illumination. Cones provide us with sharpness of vision. The peripheral retina allows us to see objects on either side (peripheral vision) and, therefore, provides the vision needed for a person to move about safely. However, because this part of the retina contains a lesser concentration of cones, it does not allow for perception of visual detail. Its larger concentration of rods provides better vision during conditions of darkness.
In contrast, the macula is a smaller, central area of the retina that contains a high concentration of cones. Accordingly, it enables clear central vision to see fine details for such activities as reading or threading a needle. The macula is particularly sensitive to circulatory changes, especially those that occur with aging, such as decreased blood flow. The retina contains a network of branching arteries, which supplies blood that carries the needed oxygen and nutrients to the retina, and accompanying veins, which then carry the blood away together with the waste products of retinal metabolism.
What is a retinal detachment?
A retinal detachment is a separation of the retina from its attachments to its underlying tissue within the eye. Most retinal detachments are a result of a retinal break, hole, or tear. These retinal breaks may occur when the vitreous gel pulls loose or separates from its attachment to the retina, usually in the peripheral parts of the retina. The vitreous is a clear gel that fills 2/3 of the inside of the eye and occupies the space in front of the retina. As the vitreous gel pulls loose, it will sometimes exert traction on the retina, and if the retina is weak, the retina will tear. Most retinal breaks are not a result of injury. Retinal tears are sometimes accompanied by bleeding if a retinal blood vessel is included in the tear.
Once the retina has torn, liquid from the vitreous gel can then pass through the tear and accumulate behind the retina. The build-up of fluid behind the retina is what separates (detaches) the retina from the back of the eye. As more of the liquid vitreous collects behind the retina, the extent of the retinal detachment can progress and involve the entire retina, leading to a total retinal detachment. A retinal detachment almost always affects only one eye. The second eye, however, must be checked thoroughly for any signs of predisposing factors that may lead to detachment in the future.
Next: What are the signs and symptoms of a retinal detachment? »
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