Diabetic retinopathy, the most common diabetic eye disease, occurs when blood vessels in the retina change. Sometimes these vessels swell and leak fluid or even close off completely. In other cases, abnormal new blood vessels grow on the surface of the retina.
The retina is a thin layer of light-sensitive tissue that lines the back of the eye. Light rays are focused onto the retina, where they are transmitted to the brain and interpreted as the images you see. The macula is a very small area at the center of the retina. It is the macula that is responsible for your pinpoint vision, allowing you to read, sew or recognize a face. The surrounding part of the retina, called the peripheral retina, is responsible for your side—or peripheral—vision.
Diabetic retinopathy usually affects both eyes. People who have diabetic retinopathy often don’t notice changes in their vision in the disease’s early stages. But as it progresses, diabetic retinopathy usually causes vision loss that in many cases cannot be reversed.
Patients with diabetes mellitus can develop serious ocular complications that can affect their vision. Over time, high blood sugar causes damage to the retinal blood vessels. Several complications may develop, including swelling in the central retina and poor blood flow. Other complications of diabetic retinopathy include retinal hemorrhages and cotton wool spots (small white spots in the retina that form because of poor blood flow).
Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is the most frequent cause of vision loss among people 50 years and older in the Western world. Many older people are unaware that they have AMD and may not notice that their vision is deteriorating, particularly if only one eye is affected. Other people may fail to report vision loss because they believe it to be an inevitable consequence of aging. If patients with certain types of AMD are to benefit from recent developments in treatment, it is important that the condition be diagnosed as early as possible.
Age-related macular degeneration is a deterioration or breakdown of the eye’s macula. The macula is a small area in the retina — the light-sensitive tissue lining the back of the eye. The macula is the part of the retina that is responsible for your central vision, allowing you to see fine details clearly.
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The retina is the nerve layer that lines the back of the eye. If you think of the eye as a camera, the retina is the film in the camera. A clear gel called the vitreous fills up the inside cavity of the eye and is located just in front of the retina. As one ages, the vitreous gel contracts and liquefies. As this occurs, the vitreous gel may sometimes pull a tear in the retina. Fluid from inside the eye can leak through the tear, and the retina can separate from the back wall of the eye, creating a retinal detachment.
It is a serious condition that may lead to blindness if not treated appropriately. Risk factors for retinal detachment include nearsightedness (myopia), history of cataract surgery, family history of retinal detachment, retinal detachment in the other eye, and weak areas in the retina such as lattice degeneration. Symptoms of a retinal detachment include onset of floaters, flashing lights, and a “curtain” or area of darkness that may encroach on vision from the side.
The middle of our eye is filled with a clear gel called vitreous (vi-tree-us) that is attached to the retina. Sometimes tiny clumps of gel or cells inside the vitreous will cast shadows on the retina, and you may sometimes see small dots, specks, strings or clouds moving in your field of vision. These are called floaters. You can often see them when looking at a plain, light background, like a blank wall or blue sky.
As we get older, the vitreous may shrink and pull on the retina. When this happens, you may notice what look like flashing lights, lightning streaks or the sensation of seeing “stars.” These are called flashes.
Retinal Tear and Retinal Detachment
Usually, the vitreous moves away from the retina without causing problems. But sometimes the vitreous pulls hard enough to tear the retina in one or more places. Fluid may pass through a retinal tear, lifting the retina off the back of the eye — much as wallpaper can peel off a wall. When the retina is pulled away from the back of the eye like this, it is called a retinal detachment.
The retina does not work when it is detached and vision becomes blurry. A retinal detachment is a very serious problem that almost always causes blindness unless it is treated with detached retina surgery.
A macular hole is a defect in the center of the macular area of the retina. The macula gives us sharp central vision and reading vision. The very center portion of the macula, called the fovea, is the thinnest portion of the entire retina. It is in this very delicate foveal area that a macular hole can develop.
In most cases, a macular hole develops as a result of anatomical changes that occur spontaneously and not from anything that the patient has done. This type of macular hole occurs most commonly in individuals over 50 years of age and is called an idiopathic macular hole. Occasionally, severe blunt trauma can cause a macular hole. A macular hole can also be seen in a very small percentage of people with retinal detachment, or in conditions that cause severe edema (swelling) of the retina.
A macular hole causes loss of sharp “straight-ahead” vision and reading vision. In the early stages of macular hole formation, the hole is very small and the central vision may be only slightly blurred or distorted. As the hole enlarges, the vision becomes progressively worse. The hole typically enlarges to a point at which the affected eye can only see the larger letters of an eye chart. A macular hole does not cause complete blindness and does not affect the peripheral (side) vision.
Retinal Vascular Disease
Blood vessels carry blood to and from the light sensitive structure in the back of the eye called the retina. Blood from the retina is drained from smaller branches of retinal veins into the larger central retinal vein and away from the eye. A retinal vein occlusion occurs when one of these veins is blocked or obstructed. Symptoms of retinal vascular disease are sudden blurring or loss of vision in all or part of one eye.
Floaters and Flashes
You may sometimes see small specks or clouds moving in your field of vision. These are called floaters. You can often see them when looking at a plain background, like a blank wall or blue sky. Floaters are actually tiny clumps of cells or material inside the vitreous, the clear, gel-like fluid that fills the inside of your eye.
While these objects look like they are in front of your eye, they are actually floating inside it. What you see are the shadows they cast on the retina, the layer of cells lining the back of the eye that senses light and allows you to see. Floaters can appear as different shapes, such as little dots, circles, lines, clouds or cobwebs. When the vitreous gel pulls on the retina, you may see what look like flashing lights or lightning streaks. These are called flashes. You may have experienced this same sensation if you have ever been hit in the eye and seen “stars.” The flashes of light can appear off and on for several weeks or months. As we grow older, it is more common to experience floaters and flashes as the vitreous gel changes with age, gradually pulling away from the inside surface of the eye.
Glaucoma is a disease that damages the eye’s optic nerve. The optic nerve is connected to the retina — a layer of light-sensitive tissue lining the back of the eye — and is made up of many nerve fibers, like an electric cable is made up of many wires. It is the optic nerve that sends signals from your retina to your brain, where these signals are interpreted as the images you see.
In the healthy eye, a clear fluid called aqueous (pronounced AY-kwee-us) humor circulates inside the front portion of your eye. To maintain a constant healthy eye pressure, your eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of your eye. If you have glaucoma, the aqueous humor does not flow out of the eye properly. Fluid pressure in the eye builds up and, over time, causes damage to the optic nerve fibers. Glaucoma can cause blindness if it is left untreated. Only about half of the estimated three million Americans who have glaucoma are even aware that they have the condition. When glaucoma develops, usually you don’t have any early symptoms and the disease progresses slowly. In this way, glaucoma can steal your sight very gradually. Fortunately, early detection and treatment (with glaucoma eyedrops, glaucoma surgery or both) can help preserve your vision.