Retinal Disorders

Introduction
Retinal Detachment
Retinoblastoma
Diabetic Retinopathy

The retina is a layer of tissue in the back of your eye that senses light and sends images to your brain. In the center of this nerve tissue is the macula. It provides the sharp, central vision needed for reading, driving and seeing fine detail. Retinal disorders affect this vital tissue. They can affect your vision, and some can be serious enough to cause blindness. Examples are

• Retinal detachment - a medical emergency, when the retina is pulled away from the back of the eye
• Macular pucker - scar tissue on the macula
• Macular hole - a small break in the macula that usually happens to people over 60
• Floaters - cobwebs or specks in your field of vision

The retina is the light-sensitive tissue that lies smoothly against the inside back wall of your eye and sends messages to your brain through your optic nerve. 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 the choroid.

Retinal detachment is a medical emergency, and time is critical. Unless the detached retina is promptly surgically reattached, this condition can cause permanent loss of vision in the affected eye.

The good news is that warning signs often appear before retinal detachment occurs, and early diagnosis and treatment by a specialist trained in eye diseases and conditions (ophthalmologist) can save your vision.

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 seem to float before your eyes
• Sudden flashes of light in one or both eyes
• A shadow or curtain over a portion of your visual field
• A sudden blur in your vision

If you experience any of these signs or symptoms, seek urgent evaluation by an ophthalmologist. In most cases, these signs and symptoms don't indicate a serious problem. However, if you do have a retinal tear or retinal detachment, prompt treatment is necessary to preserve your vision.

Retinal detachment may be caused by trauma, advanced diabetes or an inflammatory disorder. But it often occurs spontaneously, as a result of changes in the jelly-like vitreous that fills the vitreous cavity of your eye.

As you age, your vitreous may change in consistency and partially liquefy or shrink. Eventually, the vitreous may sag and separate from the surface of the retina — a common condition called posterior vitreous detachment (PVD), or vitreous collapse. This occurs to some extent in most people's eyes as they age.

PVD usually doesn't cause serious problems, but it can cause visual symptoms. 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 shifting or sagging vitreous may also cause the appearance of new or different floaters in your field of vision. These 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 and hardly ever require treatment. However, the sudden onset of floaters can signal the development of a retinal tear, particularly when accompanied by flashes of light. This occurs when the pulling of the sagging vitreous becomes strong enough to tear the retina, leaving what looks like a small, jagged flap.

Retinal detachment occurs when vitreous liquid (vitreous humor) leaks through the tear and accumulates underneath the retina. Leakage can also occur through tiny holes where the retina has thinned due to aging or other retinal disorders. Less commonly, fluid can leak directly underneath the retina, without a tear or break.

As liquid collects, areas of the retina can peel away from the underlying 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.

Most retinal tears caused by PVD lead to retinal detachment if left untreated. Detachments that go undetected and untreated can progress and eventually involve the entire retina, causing complete loss of vision.

Your risk of developing a detached retina generally increases with age simply because the vitreous changes as you grow older. The condition tends to affect more whites than blacks. The following factors also increase your risk of retinal detachment:

• Previous retinal detachment in one eye
• A family history of retinal detachment
• Extreme nearsightedness (myopia)
• Previous eye surgery, such as cataract removal
• Previous severe eye injury or trauma
• Weak areas in the periphery of your retina

An ophthalmologist can look carefully at your eye with special instruments to determine what's causing your visual symptoms. It's possible to tell if you have a retinal hole, tear or detachment by looking at your retina with an ophthalmoscope — an instrument with a bright light and powerful lens that allows your doctor to view the inside of your eyes in great detail and in three dimensions.

If blood in your vitreous cavity prevents a clear view of the retina, your ophthalmologist might also use sound waves (ultrasonography) to assess your retina. Ultrasonography is a painless test that sends sound waves through your eye to bounce off the retina. The returning sound waves create an image on a monitor that allows your doctor to determine the condition of the retina and other structures inside your eye. This test usually provides the information your doctor needs to determine whether your retina is detached.

Surgery is the only effective therapy for a retinal tear, hole or detachment. Your ophthalmologist can tell you about the various risks and benefits of your treatment options. Together you can determine what treatment is best for you.

If a tear or a hole is treated before detachment develops or if a retinal detachment is treated before the central part of the retina (macula) detaches, you'll probably retain much of your vision.

Surgery for retinal tears
When a retinal tear or hole hasn't yet progressed to detachment, your eye surgeon may suggest an outpatient procedure, which can usually prevent retinal detachment and preserve almost all vision. Healing typically takes about two weeks. Your vision may be blurred briefly following either of these procedures:

• Laser surgery (photocoagulation). During photocoagulation your surgeon directs a laser beam through a special contact lens or through a special ophthalmoscope to make burns around the retinal tear. The burns cause scarring, which usually "welds" the retina to the underlying tissue. This procedure requires no surgical incision, and it causes less irritation to your eye than does cryopexy.
• Freezing (cryopexy). With cryopexy your surgeon uses intense cold to freeze the retina around the retinal tear. After a local anesthetic numbs your eye, a freezing probe is applied to the outer surface of the eye directly over the retinal defect. This freezes the area around the hole, and the resulting delicate scar helps secure the retina to the eye wall. Cryopexy is used in instances where the tears are more difficult to reach with a laser, generally along the retinal periphery. Your eye may be red and swollen for some time after cryopexy.

Surgery for retinal detachment
Doctors commonly use one of three surgical procedures to repair a retinal detachment. Some of these procedures are done in conjunction with photocoagulation or cryopexy. The purpose of these treatments is to close any retinal holes or tears and to reduce the tug on the retina from a shrinking vitreous. The type, size and location of any retinal detachment will determine which procedure your eye surgeon recommends. In general, these surgeries can successfully treat more than 90 percent of cases of retinal detachment, although a second treatment is sometimes necessary.

• Pneumatic retinopexy. This surgical technique is generally used for a relatively uncomplicated detachment when the tear is located in the upper half of the retina. It's usually done on an outpatient basis under local anesthesia. Often your surgeon initially will treat the retinal tear with cryopexy. Then, to soften the eye, he or she may withdraw a small amount of fluid from the space between the domed clear area at the front of your eye (cornea) and the colored part of your eye (iris). Next, your surgeon injects a bubble of expandable gas into the vitreous cavity. Over the next several days, the gas bubble expands, sealing the retinal tear by pushing against it and the detached area that surrounds the tear. With no new fluid passing through the retinal tear, fluid that had previously collected under the retina is absorbed, and the retina is able to reattach itself to the back wall of your eye.

  You may have to hold your head in a cocked position for a few days after surgery, to make sure the gas bubble seals the retinal tear. And it may take several weeks for the bubble to disappear completely. Until the gas is gone from your eye, avoid lying or sleeping on your back. This keeps the bubble away from your lens and reduces the risk of cataract formation or a sudden pressure increase in your eye.

  During this time, you can't travel by airplane or be at a high altitude because a sudden drop in atmospheric or cabin pressure would cause the gas bubble to expand rapidly, resulting in a dangerously high pressure in your eye. The gases used in general anesthesia can cause similar problems. Talk to your anesthesiologist if you have to undergo general anesthesia for some unrelated problem. Check with your eye surgeon to find out when these dangers have passed.

  The success rate of pneumatic retinopexy isn't as good as that of another procedure — scleral buckling. However, it can avoid both a trip to the operating room and the need for more invasive surgery (incisional surgery).

  Complications of pneumatic retinopexy may include recurring retinal detachment, scar tissue formation in the vitreous and retina, cataracts, increased pressure inside your eyeball (glaucoma), gas under the retina, and infection. These complications are rare, but if they do occur and go untreated, they can cause severe loss of vision. A retinal detachment that has recurred can usually be repaired with another surgical procedure.

• Scleral buckling. This is the most common surgery for repairing retinal detachment. It's usually done in an operating room under local or general anesthesia. If you have an uncomplicated retinal detachment, this surgery may be done on an outpatient basis.

  First your surgeon treats the retinal tears or holes with cryopexy. Then he or she attaches a tiny silicone band (buckle) to the white of your eye (sclera) over the affected area. The silicone material is in the form of either a soft sponge or a solid piece. The buckle closes the tear and helps reduce the traction on the retina, which prevents further vitreous pulling and separation. When you have several tears or holes or an extensive detachment, your surgeon may create an encircling scleral buckle around the entire circumference of your eye.

  The scleral buckling material is stitched to the outer surface of the sclera. Before tying the sutures that hold the buckle in place, the surgeon may make a small cut in the sclera and drain any fluid that has collected under the detached retina. The buckle usually remains in place for the rest of your life. Some surgeons may choose a temporary buckle for simple retinal detachments, using a small rubber balloon that's inflated and later removed.

  A reattached retina doesn't guarantee normal vision. How well you see after surgery depends in part on whether the central part of the retina (macula) was affected by the detachment before surgery, and if it was, for how long a period. Your sight isn't likely to return to normal if the macula was detached.

  Although scleral buckling is generally successful, sometimes the retina fails to reattach. Most commonly this is because of scar tissue that forms on the retinal surface. Scar tissue present even before the operation can pull on the retina and prevent it from reattaching. The pull of scar tissue that forms after the operation can cause the retina to separate again after having been attached during surgery. This usually happens in the first couple of months after surgery.

  This condition is treated by removing the scar tissue with a procedure called vitrectomy. It may also be treated with another scleral buckling operation. In some complicated cases, the surgeon injects air, other gases or silicone oil into the vitreous cavity to push the retina back against the wall of the eye. Eventually the eye absorbs the air or gas and replaces it with fluid that the eye normally produces. Silicone oil, however, isn't absorbed and needs to be removed once the retina is reattached and healed completely.

  Complications occur infrequently in scleral buckling but can result in the need for more surgery, the loss of some or all vision in the involved eye, or in rare instances, the loss of that eye. Complications include bleeding under the retina or into the vitreous cavity, glaucoma, and sometimes scarring on the surface of the eye that can lead to problems with the muscles that control eye movements. This can cause double vision (diplopia) and may require corrective surgery.

• Vitrectomy. Occasionally, bleeding or inflammation clouds the vitreous and blocks the surgeon's view of the detached retina. In other instances, scar tissue makes it impossible to repair a retinal detachment with pneumatic retinopexy or scleral buckling alone. In these situations, your doctor may recommend removing the clouded vitreous or scar tissue with vitrectomy — a procedure that involves making a tiny incision in the sclera of your eye.

  Your surgeon accomplishes this with a variety of delicate instruments passed into the eyeball through small openings in the sclera. These instruments include a light probe that illuminates the inside of your eye, a cutter to remove vitreous or scar tissue, and an infusion tube that replaces the volume of removed tissue with a balanced salt solution to maintain the normal pressure and shape of the eye.

  After completing the vitrectomy, your surgeon may perform a scleral buckling procedure and may fill the inside of your eye with air, gas or silicone oil to help seal the retina against the wall of your eye.

  Vitrectomy surgery typically lasts more than an hour but may take several hours in more complex cases. The complex cases are often done under general anesthesia, but shorter procedures are usually performed under local anesthesia.

  After surgery, you may experience some discomfort and a scratchy sensation in your eye. Severe pain is unlikely. If it occurs, let your surgeon know right away. You can expect your eye to be red, swollen, watery and slightly sore for up to a month following any surgery for retinal detachment. Wearing an eye patch may provide some relief. Your doctor may also prescribe antibacterial or dilating eyedrops to help the healing process. You'll have to avoid strenuous activities during this time. It takes about 10 weeks for your eye to heal fully. Then your doctor will examine your eyes to assess your vision and, if you wear eyeglasses, determine whether you need a new prescription.

  Your vision may take many months to improve after surgery to repair a complicated retinal detachment. Some people don't recover any lost vision.

  The complications of vitrectomy are similar to those for other types of retinal detachment surgery. They include a retinal tear, recurring detachment of the retina, a cataract or an infection. Any of these complications can lead to partial or complete loss of vision in the affected eye or, rarely, loss of the eye itself. How much vision you retain depends on the severity of the detachment.

Retinoblastoma is a rare cancer that occurs in the eyes of young children. Tumors appear on the retina, the "movie screen" that covers the rear inside wall of the eyes. These tumors can make a child's pupil look white instead of black.

In the United States and northern Europe, retinoblastoma occurs once in every 15,000 to 16,000 births. About a quarter of the cases are hereditary and have been linked to a specific gene mutation. The cancer can occur in one or both eyes.

Fatal if left untreated, the tumors can spread to the brain via the optic nerve. Treatment for retinoblastoma can include chemotherapy, radiation and surgery. In some cases, the eye must be removed. The overall five-year survival rate for children with retinoblastoma in the United States is 93 percent.

A retinoblastoma tumor can usually be seen with a flashlight. It may first be noticed in flash photographs. Instead of the usual "red eye," the child's pupil will look white.

Retinoblastoma may also cause lazy eye (strabismus), a condition in which the eyes don't appear to look in the same direction.

Less common signs and symptoms include:

• Vision problems
• Eye pain
• Redness of the white part of the eye
• A pupil that doesn't contract when exposed to bright light

Each cell in the body carries the same set of genes. Retinoblastoma is caused by a mutation in one of these genes. In about 60 percent of the cases, this gene mutation occurs in a single cell in the eye, so only that eye develops a tumor. These sporadic mutations may be random errors that occur during normal cell division.

In the remaining 40 percent of cases, the gene mutation occurs in every cell of the body. This form of retinoblastoma is called hereditary, because it can be passed on to future generations. Oddly enough, only 25 percent of children with hereditary retinoblastoma inherit it from their parents. The others develop the mutation in all their cells after conception, while they're in the womb.

If either parent had the hereditary form of retinoblastoma, their child would have a 50 percent chance of inheriting the mutated gene that causes the disorder. Doctors recommend that these children receive eye exams every few months until the age of 3. A blood test can determine if the child has inherited the gene for retinoblastoma.

With the hereditary form of the disease, having retinoblastoma in one eye increases the risk of developing it in the other eye. Most children with hereditary retinoblastoma get tumors in both eyes at the same time. In some cases, however, one eye will develop retinoblastoma a year or more before the other eye.

Neither race nor sex seems to be a factor in developing retinoblastoma.

The ophthalmologist will need to look very carefully inside your child's eyes. Because small children have a hard time submitting to such an exam, your child may be given anesthesia so he or she will sleep through the procedure.

In most cases, the specialist can identify retinoblastoma just by looking at it with special lights and magnifying lenses. Imaging tests can help determine how large the cancer is and if it has spread. These tests include:

• Ultrasound. If the tumor is so large that the doctor can't see the entire interior of the eye, ultrasound may be used, because of its ability to see through tissue.
• Computerized tomography (CT). To highlight details on the CT scan, a harmless dye may be injected before the X-rays are taken. CT scans often are used for rapid assessment of abnormalities.
• Magnetic resonance imaging (MRI). An MRI can show more detail than a CT scan, but an MRI takes longer to perform. Because it is difficult for young children to hold still, your child may have to be sedated for an MRI.

The type of treatment chosen depends on many factors, including the size of the tumor and whether one or both eyes are affected. According to the American Cancer Society, more than 90 percent of children with retinoblastoma can be cured. The odds are even better for children whose tumors haven't spread outside the eyeball.

If retinoblastoma affects just one eye, the tumor often grows so large that it permanently destroys vision in that eye. In these cases, the most common procedure is to remove the eye. An artificial eye can be fashioned to match the child's remaining eye.

When retinoblastoma affects both eyes, doctors may use a variety of treatments in an effort to preserve as much vision as possible. They include:

• External radiation. Beams from a radiation machine are focused on the retina. Treatments are typically given five days a week for three or four weeks. Each treatment takes just a few minutes. One of the risks of this type of therapy is that it can inhibit the growth of bone and other tissues near the eye. It also may make your child more likely to develop other types of cancers.
• Internal radiation. Radioactive material is temporarily placed inside the eye socket, next to the eyeball. Your child is asleep during the operations to insert and remove the radioactive material — which is left in the eye socket for four or five days. This procedure is used only with small tumors.
• Lasers. Cancer cells are destroyed by heat caused by laser beams, which are shot through the eye's pupil. Your child is asleep for this treatment, which is usually repeated once a month for up to three months. It's effective only for small tumors.
• Freezing (cryotherapy). A probe is cooled to very low temperatures and then placed on the outside of the eyeball, next to the tumor. The eye and eyelid might be swollen for a few days. Your child is asleep for this procedure, which must be repeated several times to be successful and is useful only for small tumors.
• Chemotherapy. Some cancer drugs are taken by mouth, while others are injected into a vein. Either way, they affect the entire body, which is helpful in fighting cancers that have spread. Retinoblastomas tend to become resistant to chemotherapy, so different combinations of drugs may be tried.

There is no way to prevent retinoblastoma, but families affected by the disorder may want to consider genetic testing. For example, if your child has retinoblastoma, you may want to test his or her siblings — especially younger ones. If they have the mutated gene, you can increase the frequency of screenings for the disorder. Treatment is most effective when the disorder is found in early stages.

Genetic testing also can determine if your child has the type of retinoblastoma that can be passed down to his or her children. This information will help your child make family planning decisions in the future.

Diabetes affects your body from head to toes. This includes your eyes. The most common and most serious eye complication of diabetes is diabetic retinopathy, which may result in poor vision or even blindness.

"Retinopathy" is the medical term for damage to the tiny blood vessels (capillaries) that nourish the retina, the tissue at the back of your eye that captures light and relays information to your brain. These blood vessels are often affected by the high blood sugar levels associated with diabetes.

Nearly half of people with known diabetes have some degree of diabetic retinopathy. The longer you have diabetes, the more likely it is you'll develop diabetic retinopathy. Initially, most people with diabetic retinopathy experience only mild vision problems. But the condition can worsen and threaten your vision.

The threat of blindness is scary. But with early detection and treatment, the risk of severe vision loss from diabetic retinopathy is small. You can take steps to protect your sight if you have diabetes. These include a yearly eye examination and steps to keep your blood sugar, blood pressure and blood cholesterol under the best possible control.

In the early, most treatable stages of diabetic retinopathy, you usually experience no visual symptoms or pain. The disease can even progress to an advanced stage without any noticeable change in your vision.

Symptoms of diabetic retinopathy may include:

• "Spiders," "cobwebs" or tiny specks floating in your vision
• Dark streaks or a red film that blocks vision
• Vision loss or blurred vision
• A dark or empty spot in the center of your vision
• Poor night vision
• Difficulty adjusting from bright light to dim light

If you have diabetes, your body doesn't use sugar (glucose) properly. Sugar in your blood is vital to your health because it's a main source of energy for your body's cells. But too much sugar in your blood can cause damage throughout your body, including your kidneys, nerves, heart and eyes. Damage to the capillaries in your eyes occurs in diabetic retinopathy.

Diabetic retinopathy occurs in two types, usually affecting both eyes similarly:

• Nonproliferative diabetic retinopathy (NPDR). This type, also called background diabetic retinopathy, is an early stage of the disease. It's the most common type of retinopathy, and symptoms are often mild or nonexistent.

  In NPDR the walls of blood vessels in the retina weaken. Tiny bulges called microaneurysms (mi-kro-AN-u-riz-umz) protrude from the walls of the small vessels in the retina. Another term for these microaneurysms is "outpouchings." The microaneurysms may begin to leak, oozing fluid and blood into the retina. As NPDR progresses, other signs of damage appear. These include swelling or beading of some of the larger retinal veins and patches of swollen nerve fibers, which are called cotton-wool spots because they look like fluffy wisps of cotton.

  Mild NPDR may not affect your ability to see clearly. Vision problems from more severe NPDR are usually the result of swelling (edema) of the central part of the retina (macula) — a condition called diabetic macular edema (DME) — or the closing of capillaries, which reduces blood flow to the macula (macular ischemia). When the macula can't function properly, your central vision decreases.

• Proliferative diabetic retinopathy (PDR). This is the more advanced form of the disease. Retinopathy becomes proliferative when abnormal new blood vessels grow (proliferate) in the retina or the optic disc. The blood vessels also can grow into the vitreous, the clear, jelly-like substance that fills the center of your eyes.

  This abnormal growth generally follows the widespread closing of capillaries in the retina. The condition can cause vision loss affecting both your central and peripheral vision. The new blood vessels may leak blood into the vitreous, which clouds or even blocks your vision. Other complications include detachment of the retina due to scar tissue formation (traction retinal detachment) and a form of glaucoma associated with the growth of abnormal blood vessels on the iris, the colored portion of the eye surrounding the pupil (neovascular glaucoma).

Blurred vision in diabetes
Blurred vision can be brought on by rapid fluctuations in blood sugar. Prolonged periods of elevated blood sugar cause sugar and its breakdown products to accumulate in the lens. This accumulation sucks up water and makes the lens swell, resulting in nearsightedness — meaning distant objects appear blurry. The nearsightedness subsides once your blood sugar is brought under steady control.

Blurred vision can also be caused by macular swelling (edema), regardless of your blood sugar level. This is cause for greater concern because macular edema often develops in people with diabetic retinopathy. The swelling may fluctuate during the day, making your vision get better or worse. If blood vessels in your eye are hemorrhaging, you might notice spots floating in your field of vision. These small spots are often followed within a few days or weeks by larger spots or clouds, which are caused by more marked hemorrhaging.

Having diabetes puts you at risk of retinopathy, whether you have type 1 diabetes or type 2 diabetes. Your risk increases the longer you have the disease.

Other risk factors for diabetic retinopathy include:

• Poorly controlled blood sugar levels
• High blood pressure
• High blood cholesterol
• Pregnancy
• Hispanic or African-American heritage

Your eye doctor will likely diagnose diabetic retinopathy, either nonproliferative or proliferative, if an eye examination reveals any of the following:

• Leaking blood vessels
• Retinal hemorrhage
• Swollen retina
• Fatty deposits (exudates) in the retina
• Areas of nerve fiber damage (cotton-wool spots)
• Changes in blood vessels, such as closures, beading or loops
• Microaneurysms
• Formation of new blood vessels (neovascularization)
• Vitreous hemorrhage
• Scar tissue formation with retinal detachment

As part of an eye examination, your doctor may include a diagnostic procedure called fluorescein angiography to identify leaking blood vessels.

In fluorescein angiography, your doctor injects a dye into a vein in your arm. The dye circulates through your eyes, making the blood vessels in your retina easy to identify. Your doctor can pinpoint areas where normal blood vessels have become closed or have broken down and are leaking fluid. A camera with special filters takes flash pictures every few seconds for several minutes, providing your doctor with useful images.

Your doctor also may request an optical coherence tomography (OCT) examination. This noninvasive imaging scan provides high resolution images of the retina that show, for example, the thickness of the retina and whether fluid has leaked into retinal tissue. OCT exams can be useful both as a diagnostic tool and as a way of monitoring treatment effectiveness.

If you have mild nonproliferative diabetic retinopathy, you may not require treatment right away. However, your eye doctor will want to closely monitor your retina. Proliferative diabetic retinopathy requires prompt surgical treatment.

The two main treatments for diabetic retinopathy are photocoagulation and vitrectomy. In many cases, these treatments are effective and slow or stop the progression of the disease for some time. But they're not a cure. Because diabetes continues to affect your body, you may experience further retinal damage and vision loss at a later time.

Photocoagulation
The goal of photocoagulation, also known as laser treatment, is to stop the leakage of blood and fluid in the retina and thus slow the progression of diabetic retinopathy and vision loss. The decision to use the procedure depends on the type of diabetic retinopathy you have, its severity and how well it may respond to treatment.

Your doctor may recommend photocoagulation if you have:

• Diabetic macular edema, a swelling that involves or threatens the center of the retina
• Severe nonproliferative diabetic retinopathy, especially if you have type 2 diabetes
• Proliferative diabetic retinopathy
• Neovascular glaucoma

In photocoagulation, a high-energy laser beam creates small burns in areas of the retina with abnormal blood vessels to help seal any leaks. The procedure takes place in your doctor's office or in an outpatient surgical center. Before surgery your eye doctor dilates your pupil and applies anesthetic drops to numb your eye. In some cases he or she numbs your eye more completely by injecting anesthetic around and behind your eye.

First, your chin and forehead are rested in an examination device called a slit lamp. This is a microscope that uses an intense line of light (slit) to allow your doctor to clearly view portions of your eye. Then, your doctor places a medical contact lens on your cornea — the layer of clear tissue at the front of your eye — to help focus laser light onto the sections of the retina to be treated. Fluorescein angiographic photographs may serve as maps to show where the laser burns should be placed. During the procedure you may see bright flashes from the short bursts of high-energy light.

To treat macular edema, the laser is focused on spots where blood vessels are leaking near the macula. The doctor makes "spot welds" to stop the leakage. If the leaks are small, the laser is applied directly to specific points where the leaks occur (focal laser treatment). If the leakage is widespread or diffuse, laser burns are applied in a grid pattern over a broad area (grid laser treatment).

Shortly after laser treatment, you can usually return home, but you won't be able to drive, so make sure to arrange for a ride. Your vision will be blurry for about a day. Even when laser surgery is successful in sealing the leaks, new areas of leakage may appear later. For this reason you'll have follow-up visits and, if necessary, additional laser treatments.

Immediately following laser surgery to treat macular edema, small spots caused by the laser burns may appear in your visual field. The spots generally fade and disappear with time. If you had blurred vision from macular edema before surgery, you may not recover completely normal vision.

Panretinal photocoagulation
For proliferative diabetic retinopathy, doctors use a form of laser surgery called panretinal or scatter photocoagulation. With this technique the entire retina except the macula is treated with scattered laser burns. The treatment causes the abnormal new blood vessels to shrink and disappear. Thus it reduces the chances of a vitreous hemorrhage and traction retinal detachment. Panretinal photocoagulation is usually done in two or more sessions.

You may notice some loss of peripheral vision afterward. Panretinal photocoagulation is a trade-off. Some of your side vision is sacrificed to save as much of your central vision as possible. You may also notice difficulties with your night vision.

Vitrectomy
A vitreous hemorrhage may clear up on its own. But if the hemorrhage is massive and doesn't clear, a vitrectomy may help to restore your sight and may allow the application of needed laser treatment.

In this procedure your surgeon uses delicate instruments to remove the blood-filled vitreous. A vitreous cutter cuts the tissue and removes it, piece by piece, from your eye. The tissue that is removed is replaced with a balanced salt solution to maintain the normal shape and pressure of the eye. A light probe illuminates the inside of the eye. The surgeon performs the procedure while looking through a microscope suspended over the eye. In this way the vitreous blood is removed to re-establish clear vision.

A vitrectomy is also used to remove scar tissue when it begins to pull the retina away from the wall of the eye. This allows a detached retina to settle back and flatten out. Your eye doctor may decide not to operate on a retina detached by scar tissue if the detachment is located away from the macula and doesn't appear to be progressing.

During a vitrectomy the surgeon may also use a laser probe to perform panretinal photocoagulation. This can help prevent renewed growth of abnormal blood vessels, bleeding and scar tissue formation.

Vitrectomy can be performed under local or general anesthesia. Sometimes it is necessary to inject a bubble of expandable gas into the eye cavity. As the gas bubble expands, it pushes on the retina and helps it reattach. You may be required to remain in a face-down position for several days until the gas bubble spontaneously goes away. Your eye will be red, swollen and sensitive to light for some time after surgery. For a short time afterward, you'll need to wear an eye patch and apply medicated eyedrops to help the healing. Full recovery may take weeks.