Retinal Diseases

Retinal diseases specifically affect the retina — a layer of tissue at the back of the eye that is responsible for vision. These diseases can affect the retina, the macula (area of central vision), or the fovea at the center of the macula. Many retinal diseases share common symptoms and treatments, but each has unique characteristics.


Diagnosis

The diagnosis of a retinal disease is usually made based on a thorough eye exam by an ophthalmologist. An ophthalmoscope allows the doctor to view the inside of the eyes in three dimensions. The ophthalmologist looks for presence of abnormalities anywhere in the eye. Additional tests may be done to determine the location and extent of the disease.

Amsler Grid Test
The physician may use a printed grid to test clarity of central vision. The doctor will ask if the lines of the grid seem faded, broken or distorted, and will take note of where the distortion occurs on the grid. By evaluating the location of the distortion, the physician will better understand the extent of retinal damage caused by disease.

Optical Coherence Tomography (OCT)
Similar in principle to ultrasonography, OCT relies on light waves slicing through tissue layers in the back of the eye. They produce a "backscattering" that converts into high-resolution, cross-sectional images of the retina, macula and optic nerve. Particularly useful in investigating abnormal tissue, With this new medical imaging technology, clinicians have another painless, precise diagnostic tool.

Fluorescein Angiography
To get more information about a suspected retinal disease, the doctor may use fluorescein angiography to identify leaking blood vessels. First, the doctor injects dye into a vein in the patient's arm. As the dye circulates through the bloodstream and eventually to the eye, the blood vessels in the retina stand out as bright yellow when observed with a special blue light. A camera takes flash photographs of the eye every few seconds for several minutes. The images help identify the blood vessels, new abnormal blood vessels and subtle pigmentation changes in the back of the eye.

Indocyanine Green Angiography (ICGA)
Another type of angiography of the vessels in the eye is ICG. ICG is a dye that lights up when exposed to infrared light. Infrared light is used to take pictures of the back of the eye visualizing retinal blood vessels, and the deeper, harder to see choroidal blood vessels.

Ultrasound
An ophthalmologist can usually find evidence of retinal disease with the ophthalmoscope, but occasionally blood or other problems in the eye prevents a clear view of the retina. In these cases, the doctor may use ultrasound, a painless test that uses sound waves to get a precise picture of the retina. Ultrasound is also used to measure the size of growths in the back of the eye.


Treatment

The goal of many treatments is to stop further progression of the disease. In most cases, the damage that has already occurred cannot be reversed, making early detection very important for vision preservation.

The physician will recommend one of the following treatments:

Photocoagulation
In photocoagulation, the surgeon creates small burns in the retina using a high energy laser. For a retinal tear or hole, the goal is to create scar tissue around the tear, which usually holds the retina to the underlying tissue. For diabetic retinopathy, the burns help seal off the abnormal blood vessels, stopping leakage of blood and fluid into the eye.

Creating burns on the retinal surface will cause blind spots, but photocoagulation is nearly always done on the peripheral surface of the retina. Any blank spots or loss of vision will occur in the peripheral vision, leaving central vision intact.

Panretinal Photocoagulation
Panretinal photocoagulation is a procedure used for proliferative diabetic retinopathy where abnormal new blood vessel growth is diffuse and causes bleeding into the vitreous. With this technique, the retina (except the macula, responsible for central vision) is treated with laser burns. These burns cause the new blood vessels to shrink and disappear, but the burns cause some peripheral vision loss. By sacrificing some side vision, surgeons can preserve as much central vision as possible.

Cryopexy
In cryopexy, the surgeon uses intense cold to freeze the area around a retinal tear or hole. This causes scarring which seals the hole and holds the retina to the underlying tissue to prevent fluid from passing through the tear, leading to retinal detachment.

Pneumatic Retinopexy
Pneumatic retinopexy is a treatment for retinal detachment. This surgery can be performed on uncomplicated retinal detachments with tears located in the upper half of the retina. First, cryopexy is performed around the retinal tear to seal it off. A bubble of gas is injected into the vitreous cavity. The bubble expands over the next few days, sealing the retinal tear, and causing the retina to reattach itself to the wall of the eye. Since the bubble must push against the tear, it may be necessary for patients to keep their head in a cocked position following surgery, depending on where the tear(s) is. Until the gas is gone from the eye (two to eight weeks), the patient must avoid lying or sleeping on his or her back to guard against cataract formation or a sudden increase in eye pressure.

Scleral Buckling
Scleral buckling is one of the most common surgeries for repairing retinal detachment. The surgeon sews buckling material (solid or spongy silicone) to the eye wall causing localized indenting of the sclera (eyeball) under the retinal tears. This indent, or buckle, closes the tear and changes the circumference of the eyeball, thereby preventing further pulling and separation. This procedure successfully repairs retinal detachment in more than 90 percent of cases, but preservation of vision depends on how the macula was affected before surgery. In some cases, some vision may be lost due to wrinkling or puckering of the macula. See Epiretinal membrane.

Vitrectomy
When the back part of the eye is entered to treat a problem, the surgery is referred to as vitrectomy. During this procedure the eye is entered through tiny incisions and the vitreous gel is removed, followed by additional surgical steps, as necessary. Sometimes cloudy vitreous is removed as the only surgical goal. In other instances, peeling of scar tissue, laser photo coagulation, scleral buckle placement, gas injection or other steps are undertaken.

Soft Tissue Sarcoma

Sarcoma is cancer of the connective tissue such as muscle, cartilage, blood vessels, nerves and bones. Soft tissue (non-bone) sarcomas are rare, but they can occur in many parts of the body such as muscle or fat of the extremities or the trunk. They can also occur in the abdomen, pelvis or chest. There are many types of soft tissue sarcomas, but most are treated in the same way. Some common soft tissue sarcomas include fibrosarcoma, liposarcoma, malignant fibrous histiocytoma, rhabdomyosarcoma and synovial sarcoma.


Diagnosis

Patients often discover soft tissue sarcoma as a lump or hard mass. They often have no pain or other symptoms. A doctor should examine any lump or mass that does not go away within a few days.

Specialists use imaging studies such as X-rays, computed tomography (CT) scans, or magnetic resonance imaging (MRI) to evaluate the suspected tumor. Other imaging techniques that may be used include a chest CT, a bone scan and positron emission tomography (PET). These images are helpful in evaluating areas to which cancer commonly spreads (metastasizes).

To diagnose soft tissue sarcoma, the doctor removes a small piece of the suspected tumor for examination (biopsy). A pathologist looks at the cells under a microscope to confirm their type.


Treatment

Soft tissue sarcomas are treated with surgery, chemotherapy and radiation. Usually a combination of these modalities offers the best chance to treat the disease successfully.

Soft tissue sarcomas occur more frequently in adults than in children and adolescents. About half of all cases can be successfully treated and cured. The cure rate for soft tissue sarcoma depends on such factors as:

• The patient's age and general health
• The type and grade of the sarcoma
• The size of the tumor at diagnosis
• The tumor's location in the body
• Whether the sarcoma has spread (metastasized) to other parts of the body

Surgery
Surgery may sometimes be needed to obtain tissue for diagnosis as well as to remove the tumor. Chemotherapy and radiation may be given to improve likelihood that the tumor has been successfully treated.

Chemotherapy
During chemotherapy, a combination of cancer-fighting drugs attacks soft tissue sarcoma cells wherever they may be in the body.

Radiation
Prior to surgery, radiation oncologists may apply high-energy external beam radiation to tissues containing soft tissue sarcoma prior to surgery to try to shrink tumors and kill cancer cells. Depending upon the tumor's size, shape and location, they treat tumors using 3-D conformal radiation therapy or intensity modulated radiation therapy, a highly precise technology. After removal of the tumor, intraoperative radiation therapy (IORT) may be given. IORT may involve placement of hollow tubes for insertion of brachytherapy seeds several days after the surgery. Radiation, when used with surgery, may improve control of the tumor at the initial site for most soft tissue sarcoma patients.

Urinary Obstructions

Normally, urine is formed in the kidneys, flows through the ureters to the bladder, and is released through the urethra. A urinary obstruction blocks the normal flow of urine, causing it to back up toward the kidneys. Urine flowing the wrong way in the urinary tract can cause infections and kidney damage. Urinary obstructions affect about one in every 1,000 people, and they vary widely by the cause and type of blockage.

The obstruction can involve one or both kidneys, called unilateral or bilateral obstruction. The blockage may be complete or partial, and it can occur suddenly or develop over time. An obstruction can occur in any part of the urinary tract, whether upper (kidneys and ureters) or lower (bladder and urethra). Where an obstruction is located will determine the best treatment option.


Diagnosis

The physician may order the following tests, which could reveal a urinary obstruction:

• Urinalysis
• Blood and urine tests to assess kidney function
• Abdominal X-rays

These tests check for urinary tract infection, which can result from an obstruction:

• Urine culture
• CBC test to identify increased white blood cell count

Cystoscopy
A small, flexible tube which includes an optical system is inserted into the body through the urethra. The optical system allows physicians to see inside the body.

Renal ultrasound
Sound waves are used to produce an internal view of the kidneys, ureters, bladder and urethra.

Voiding cystourethrogram
A catheter, or tube, is inserted through the urethra to fill the bladder with a liquid contrast material. Then the bladder and urethra are X-rayed before and during urination.

Intravenous pyelogram (IVP) or excretory urogram
A contrast material is injected into a vein in the arm. X-rays are taken as the contrast moves through the kidneys, ureters and bladder.

CT scan
This test uses a series of thin X-ray slices to produce two-dimensional images of the urinary system.

CT urogram
This test combines IVP with CT of the abdomen and pelvis.

Renal nuclear scan
Similar to an IVP, except a small amount of radioactive solution is injected and viewed through a special camera. This test can evaluate the kidneys, how they are functioning and if they have been injured by a urinary obstruction.

Abdominal MRI
Powerful magnets and radio waves produce detailed images of the urinary system.


Treatment

Temporary, or Short-term, Treatment

A urinary obstruction can cause acute pain or potentially serious problems if the urine is backing up into the kidneys. In these cases, the patient may need immediate relief. Depending on the location of the obstruction, these short-term treatments can include:

• A catheter (small tube) inserted through the urethra into the bladder to drain urine from the bladder.
• A stent (hollow tube) in the ureter (between the kidney and bladder) to keep the ureter open.
• A nephrostomy tube can inserted through the patient's lower back to drain urine directly from the kidney (percutaneous nephrostomy).

Cystoscopy
A cystoscope is a small, flexible tube which includes an optical system. The cystoscope is inserted into the body through the urethra. The optical system allows doctors to see inside the body and perform surgery by inserting and manipulating equipment through the tube. For patients with urinary obstruction, cystoscopy is used to diagnose urinary tract disorders, such as enlarged prostate. During the procedure, the doctor can also surgically remove obstructions such as kidney stones.


Permanent, or Long-term, Treatments

Treatment options depend on the kind of urinary obstruction and may involve medication or surgery. The benefits to patients are more rapid recovery and minimal scarring. Should the obstruction affect kiddney function, kidney specialists (nephrologists) can advise on treatment options.

If both kidneys are permanently damaged and no longer function as a result of the urinary obstruction,

Treatment of Infections
Once urine has backed up into the urinary system, it can cause an infection that is difficult to cure. Mayo Clinic urologists coordinate with the patient's primary care or local physician to closely monitor the patient for urinary tract infections and to provide treatment.

Chondrosarcoma

Bone cancer is very rare. Approximately 2000 cases of primary bone cancer are diagnosed in the United States each year. Experts consider chondrosarcoma, a cancer that affects cartilage cells, to be the second most common type (after osteosarcoma) of bone cancer. Chondrosarcoma accounts for 26 percent of primary bone cancers. Typical locations for chondrosarcoma tumors to develop are the legs, arms or pelvis of adults ages 50 to 70.


Diagnosis

X-rays and other imaging techniques such as a computed tomography (CT) or magnetic resonance imaging (MRI) are used to identify the tumor. To diagnose chondrosarcoma, the doctor removes a small sample of the suspected tumor in a procedure known as a biopsy. A pathologist looks at the sample under a microscope to determine whether the tissue contains malignant cells. A chest CT and a bone scan help the physician evaluate the lungs and other areas where the cancer may have spread (metastasized).


Treatment

After completing a thorough evaluation of the patient, the Mayo care team develops an individualized treatment strategy. Surgery is the main treatment option for chondrosarcoma. Surgical options depend upon the tumor's size, and whether the tumor has grown into or around nerves, blood vessels or a joint.

If specialists treat the cancer before it spreads (metastasizes) to other locations in the body, the cure rate is high. For individuals whose cancer has spread, treatment is more difficult and depends on the location of the disease. In certain cases chemotherapy may be recommended. For patients who have local recurrence with no evidence of metastasis, surgery plus radiation may be recommended (preoperative external beam radiation, surgery, intraoperative radiation).


Limb Salvage Techniques

Autograft
In this procedure a surgeon harvests the patient's own bone tissue from a healthy bone to implant at the site where cancerous tissue is removed. One common form of this procedure is called free vascularized fibular grafting. In this procedure surgeons harvest the smaller of the two lower leg bones, as well as its blood vessels to implant at the cancer site. Benefits of this procedure over allograft (bone graft from a donor) techniques include a greater chance for the bone to heal and a reduced chance for infection.

Allograft
Orthopedic oncologists can use bone, tendons and ligaments from a tissue bank or donor to rebuild areas where a chondrosarcoma tumor is removed. This process is called an allograft procedure.

Prosthetic Implants
Surgeons can replace sections of bone with specialized prosthetic implants. Expandable and solid implants of many different sizes are available. This may be a viable option for some chondrosarcoma patients.

Glioma

A tumor is a mass or growth of abnormal cells. Tumors found in the brain typically are categorized as primary or secondary. Primary brain tumors (gliomas) start in the brain or spinal cord tissue. They can spread within the nervous system but typically do not spread outside the nervous system.

Gliomas can be either low-grade (slow-growing) or high-grade (fast-growing). Annually, about 17,000 Americans are diagnosed with gliomas.

Treatment for brain tumors can be challenging, but many are treated successfully. New technology helps physicians target tumors more precisely and innovative treatments under investigation offer opportunity for the future.


DIAGNOSIS

Diagnosing a brain tumor usually begins with an exam by a neurologist, which includes checking vision, hearing, balance, coordination and reflexes. Depending on those results, the physician may request one or more of the tests described below. A biopsy is usually required to diagnose a brain tumor and confirm its type.

Magnetic Resonance Imaging (MRI) Scan
This scan uses magnetic fields to generate images of the brain. The patient lies inside a cylindrical machine for approximately an hour. MRI scans are particularly useful in diagnosing brain tumors, because they outline the normal brain structures in detail. Sometimes a special dye is injected into the bloodstream during the procedure to help better distinguish tumors from healthy tissue (MRI angiogram).

Computed Tomography (CT) Scan
A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. A patient lies still on a movable table that is guided into what looks like an enormous doughnut where the images are taken. A special dye may be injected into the bloodstream after a few CT scans to help better distinguish tumors (CT angiogram). A CT scan is painless and generally takes less than 10 minutes.

Angiogram
A special dye is injected into the arteries that go to the brain. The dye, which flows through the blood vessels in the brain, can be seen on X-ray. This test helps locate blood vessels in and around a brain tumor.

Other Brain Scans
Magnetic resonance spectroscopy (MRS), single-photon emission computed tomography (SPECT) or positron emission tomography (PET) scanning also help physicians gauge brain activity and blood flow. These scans can be combined with MRIs to help physicians understand a tumor's effects on brain activity and function. If a brain scan detects a tumor, especially multiple tumors, physicians may test for cancer elsewhere in the body.

X-rays of the Head and Skull
An X-ray of the head may show skull alterations indicating a tumor or calcium deposits sometimes associated with brain tumors. However, an X-ray is far less sensitive than brain scans and is used less often.

Biopsy
A biopsy is usually required to diagnose a brain tumor and confirm its type. In a biopsy, a tiny piece of tumor is removed for examination under a microscope. A biopsy can be performed separately or as part the surgery to remove the tumor.


TREATMENT

New glioma treatments are developed continually, so several options may be available for patients. The pros and cons of each option are discussed in detail during treatment planning.

Treatment options and survival odds depend on the glioma type, size and location, as well as the patient's age and overall health. For treatment specifics, see descriptions of each glioma type:

• Astrocytomas
• Ependymomas
• Glioblastoma multiforme
• Oligodendrogliomas
• Mixed gliomas

Quality of Life
As glioma treatment becomes more successful, patients live longer but also face greater risks of long-term adverse effects of treatment. The most significant adverse effects are cognitive problems. Mayo specialists, including neuropsychologists and experts in brain rehabilitation, help patients with these issues. Almost all clinical trials at Mayo Clinic and the North Central Cancer Treatment Group incorporate quality-of-life measures.

Whenever possible, the glioma treatment team integrates care from the patient's local physician and oncologists to offer the most comprehensive treatment program management.


Treatment Options


Surgery
Surgery is the initial therapy for nearly all patients with gliomas. It can cure most benign gliomas, as well as meningiomas. The goal of surgery is to remove as much of the glioma as possible while minimizing damage to healthy tissue.

Some gliomas can be removed completely; others can be removed only partially or not at all. Partial removal helps relieve symptoms by reducing pressure on the brain and reducing the size of the glioma to be treated by radiation or chemotherapy.

Direct, face-to-face contact with the pathologist during the surgery allows the surgeon to verify that the glioma has been fully removed and may reduce the need for an additional operation.

If a glioma cannot be surgically removed, the physician may do only a biopsy. A small piece of the glioma is removed so a pathologist can examine it under a microscope to determine its cell makeup. The finding helps determine the proper treatment.

Patients diagnosed with brain gliomas often can be scheduled for surgery the next day, if desired. Surgeons provide patients with information to help them decide which treatment is best for them. Surgical removal demands great skill. Mayo's neurosurgeons operate on hundreds of patients each year, using the latest technological advances. Mayo surgeons were pioneers in developing computer-assisted neurosurgery, which allows surgeons to precisely map the brain and more accurately and aggressively treat brain tumors.


Radiation Therapy
Radiation Therapy is an essential component of treatment for many patients with gliomas. It can be curative some patients and prolongs survival for most.

The traditional form of radiation therapy, referred to as fractionated radiation, delivers radiation in small doses (fractions). Typically, patients are treated once daily, five times per week, for a total of five to six weeks. Even after the tumor visible on the CT or MRI scan is removed, radiation is often used to treat the margin of brain around the surgical cavity, going after the microscopic tumor cells that have infiltrated the area from the original mass.

External Beam Radiation
This traditional form of radiation therapy delivers radiation from outside the body. The radiation usually involves treatments five days a week. The length of treatment time depends on the type of glioma. External beam radiation is less precise than Fractionalized Stereotactic Radiotherapy, but allows a wider area of tissue around the glioma to be treated.

Fractionalized Stereotactic Radiotherapy (FSR)
Fractionalized Stereotactic Radiotherapy minimizes damage to healthy tissue by carefully targeting radiation. FSR involves many small treatments instead of one big dose of radiation. Healthy brain tissues and cranial nerves that cannot tolerate a single, large treatment can tolerate many small treatments.

This treatment also offers the biological benefit of fractionation (separation into different portions) to exploit the different sensitivities of healthy versus cancerous tissue. These advantages are helpful when treating lesions near delicate structures such as the optic nerves, which cannot tolerate high levels of radiation.

For FSR, the glioma patient is fitted with a plastic mask that helps locate the glioma and target the radiation during treatment. The patient lies on a table. X-rays are taken to determine correct positioning. The treatment is given in several small units called arcs. The number of treatments depends on the size and location of the glioma.



Stereotactic Radiosurgery
Stereotactic Radiosurgery is effective for lesions such as meningioma or small brain metastases that are confined to a limited area. It spares nearby healthy tissue because radiation levels drop rapidly at the edges of the area being treated.

Radiosurgery is not typically used in the treatment of gliomas. Gliomas tend to be infiltrative tumors, so the areas around the surgical cavity or around the visible tumor mass are not ideal targets for radiosurgery. Fractionated radiation is used most often.

Chemotherapy
Chemotherapy is an important part of the care of glioma patients. For patients with glioblastoma (Grade 4 astroccytoma), the most rapidly growing and aggressive glioma, the addition of chemotherapy to the radiation has been shown to significantly extend a patient's lifespan. Current research is focused on the development and evaluation of new drugs to use with radiation for a newly diagnosed tumor, as well as for recurrent gliomas.

Macular Degeneration

Age-related macular degeneration (AMD) is a chronic eye condition that typically affects people age 50 and older, and is the leading cause of severe vision loss in those over 60. A part of the retina (the tissue at the back of the eye) called the macula specifically allows central vision, which is critical for reading and recognizing faces. When a person has macular degeneration, the macula begins to deteriorate, causing anything from blurred or slightly distorted central vision to a blind spot in the center of the visual field. There are two stages of macular degeneration: dry and wet.


DIAGNOSIS

The diagnosis of macular degeneration is made based on a thorough eye exam. Following diagnosis, additional tests may be performed to determine the location and extent of the disease.

Eye Exam
The doctor looks for presence of abnormalities in the macula, such as deposits called drusen. In addition, the appearance of the macula is important to sharp central vision — if the pigmentation is mottled or uneven, instead of its normal even reddish color, macular degeneration is usually the cause.

Amsler grid test
As a part of the eye examination, the physician may evaluate the patient's vision using a printed grid. If macular degeneration is present, the lines of the grid may seem faded, broken or distorted. By noting where the distortion occurs (usually near the center of the grid), the doctor can better determine the location and extent of macular damage.

Fluorescein angiography
After diagnosis, the physician may perform this test to determine the extent of the damage from macular degeneration. First, the doctor injects dye into a vein in the patient's arm. As the dye circulates through the bloodstream and eventually to the eye, the blood vessels in the retina stand out as bright yellow when observed with a special blue light. A camera takes flash photographs of the eye every few seconds for several minutes, which help the doctor determine pigmentation changes or abnormal blood vessels.

Indocyanine green angiography (ICGA)
Another type of angiography of the vessels in the eye is ICG. ICG is a dye that lights up when exposed to infrared light. Infrared light is used to take pictures of the back of the eye visualizing retinal blood vessels, and the deeper, harder to see choroidal blood vessels.


TREATMENT

The goal of treatment is to stop further vision loss. In most cases, the damage that has already occurred cannot be reversed, making early detection very important for vision preservation.

Dry Macular Degeneration
There is no treatment currently available to reverse dry macular degeneration. This condition normally progresses slowly, and many people are able to live relatively normal lives, especially if vision is affected only minimally.

The good news is that the progression can be slowed by taking high doses of vitamins A, C, E and the mineral Zinc. Patients should discuss with their regular doctor (see also prevention of AMD).

Wet Macular Degeneration
In wet macular degeneration, new abnormal blood vessels behind the retina begin forming at a rapid rate. These vessels begin to leak blood and fluid, causing damage to the macula, the region of the retina responsible for central vision. The doctor will prescribe treatment based on the location and extent of the abnormal blood vessels.

Anti-angiogenic medicine
After the ophthalmologist numbs the eye with an anesthetic, the drug, called pegaptanib sodium (Macugen®) is injected into the affected eye. The medicine stops or slows the blood vessels from growing, leaking and bleeding. The treatment is given every six weeks to prevent the blood vessels from causing more vision loss. This therapy causes less damage to the retina than the laser treatments described below.

Photocoagulation
Also known as laser treatment, photocoagulation uses a high-energy laser beam to create small burns in areas of the retina with abnormal blood vessels. This treatment is used when the abnormal blood vessels are not yet under the area of central vision (fovea). Because it is uncommon for the blood vessels to spare the fovea, only a small number of patients are candidates for the procedure. The doctor determines who may benefit from the treatment based on the location and appearance of the blood vessels, the amount of blood leakage, and the overall health of the macula.

Photodynamic Therapy
The location of the abnormal blood vessels often determines which treatment is selected. The macula is the central portion of the retina responsible for central vision, and the fovea is directly in the center of the macula and is responsible for the sharpest vision. If the abnormal vessels are located directly under the fovea, hot laser treatment (photocoagulation) would damage the fovea and decrease central vision. In these cases, photodynamic therapy may be an excellent option.

In this treatment, a drug called verteporfin (Visudyne®) is injected into the bloodstream. The drug concentrates in the abnormal blood vessels under the macula. The doctor then focuses cold-laser light at the macula, which activates the drug and leads to the closing off of the abnormal vessels without damage to the macula.

Macular Translocation Surgery
Although the procedure is used in rare circumstances, patients with recent visual loss associated with wet macular degeneration and who still have healthy tissue around the fovea may be candidates for macular translocation. The procedure is especially useful when there is a large amount of bleeding under the macula (an uncommon complication of wet macular degeneration).

In this procedure, the surgeon detaches the retina, shifts the fovea away from the abnormal blood vessels and relocates it over healthy tissue. With the abnormal vessels exposed (previously under the fovea), the surgeon can remove them with tiny instruments. Since the fovea has been shifted to a new location, it can function without interference from the macular degeneration changes.