What is the purpose of the CATT study?
Led by Cole Eye Institute chairman Daniel F. Martin, MD, the head-to-head trial compared the effectiveness of ranibizumab (Lucentis®) and bevacizumab (Avastin®), two anti-VEGF agents of intravitreal injections used to treat patients with neovascular age-related macular degeneration (AMD). Both drugs block growth of abnormal blood vessels and leakage of fluid from the vessels.
Most clinicians use these drugs on an as-needed basis when there is evidence of active disease, such as fluid leakage. However, in the original clinical trials for AMD, Lucentis® was administered monthly. It was unknown if as-needed dosing would produce the same long-term visual improvements that were achieved with monthly administration.
Conducted at 44 centers across the country, this landmark clinical trial not only yielded important results about the effectiveness of these two drugs in treating macular degeneration, but it also uncovered critical findings regarding the administering of as-needed injections with monthly monitoring.
CATT Study Results
- Year 1 Results: Results after the first year of the trial were released in March 2011, and showed both drugs greatly improved patients' visual acuity at almost identical levels. Additionally, results from both drugs were highly effective regardless of the dosing approach administered (monthly, less-than-monthly or as-needed).
- Year 2 Results: While study results showed slightly less vision acuity gains in patients given "as-needed" administered treatments, year two CATT study results found both drugs provide dramatic and lasting vision improvements in patients. In previous AMD treatments, only 15 percent of patients retained similar levels of visual acuity. The CATT study however showed two-thirds of patients gain 20/40 vision or better after two-years.
- Year 5 Results: Five year results found that, although vision gained during the first two years of treatment was not maintained, nearly half of patients could still see 20/40 or better after five years of treatment. Fifteen years ago, before the availability of anti-VEGF therapy, there was a high probability that almost all of these patients would be legally blind by five years, with most of them legally blind within two years. The study also confirmed the effectiveness and safety of ranibizumab and bevacizumab for treating age-related macular degeneration (AMD).
(Also known as 'Age-related Macular Degeneration', 'AMD')
Macular degeneration is an eye disease that occurs when the small central portion of the retina, known as the macula, is damaged. The retina is the light-sensing nerve tissue at the back of the eye. Because the disease develops as a person ages, it is often referred to as age-related macular degeneration (AMD).
There are two types of age-related AMD, the "dry" form and the "wet" form.
- Dry form of AMD: The "dry" form of AMD is characterized by the presence of yellow deposits, called drusen, in the macula. In general, drusen does not cause changes in vision; however, as they grow in size and increase in number, they may lead to a dimming or distortion of vision that people find most noticeable when they read. In more advanced stages of dry AMD, there is also a thinning of the light-sensitive layer of cells in the macula leading to atrophy, or tissue death. In the atrophic form of dry AMD, patients may have blind spots in their vision. In the advanced stages, patients may even lose central vision.
- Wet form of AMD: The "wet" form, or exudative neovascular form of AMD is characterized by the growth of abnormal blood vessels from the choroid underneath the macula. This is called choroidal neovascularization. These blood vessels leak blood and fluid into the eye, causing distortion of vision that makes straight lines look wavy, as well as blind spots and loss of central vision. These abnormal blood vessels eventually scar, leading to permanent loss of central vision.
Most patients with AMD have the dry form of the disease and will not lose central vision. However, the dry form of AMD can lead to the wet form. Although only about 10% of people with AMD develop the wet form, they make up the majority of those who experience serious vision loss from the disease.
Because the dry form can change into the wet form, it is very important for people with AMD to monitor their eyesight carefully and see their eye doctor on a regular basis.
Who Gets AMD?
As the name suggests, AMD is more common in older adults. In fact, it is the leading cause of severe vision loss in adults over age 60.
AMD may be hereditary, meaning it can be passed on from parents to children. If someone in your family has or had the condition you may be at higher risk for developing the disease. Talk to your eye doctor about your individual risk.
What are the symptoms?
AMD often does not have symptoms and is unrecognized until it affects both eyes. The first sign of AMD is usually distortion of straight lines. This may progress to a gradual loss of central vision.
Symptoms of AMD include:
- Straight lines start to appear distorted, or the center of vision becomes distorted
- Dark, blurry areas or white out appears in the center of vision
- Diminished or changed color perception
If you experience any of these symptoms, see an ophthalmologist as soon as possible.
How is AMD diagnosed?
One of the most common early signs of AMD is the presence of drusen -- tiny yellow deposits under the retina. Your doctor can see these during a routine eye exam. Your doctor may also ask you to look at an Amsler grid -- a pattern of straight lines that resemble a checkerboard. Some of the straight lines may appear wavy to you, or you may notice that some of the lines are missing. These can be signs of AMD. Sometimes, early AMD can even be detected using a traditional eye chart exam.
If your doctor suspects you have the rare "wet" form, or neovascular form, of AMD, you may have a procedure called fluorescein angiography. In this procedure, a dye, called fluorescein, is injected into the arm. Photographs are taken to show the movement of the dye as it reaches the eye and passes through the blood vessels of the retina. If there are new vessels leaking fluid or blood in the macula, the photographs will show their exact location and their type.
Early detection of AMD is very important because there are treatments that can delay or reduce the severity of the disease.
What treatments are available?
There is currently no cure for AMD, but treatments may prevent severe vision loss and slow the progression of the disease considerably. Several options are available, including:
- Anti-angiogenesis drugs: Ranibizumab (Lucentis®) is the first drug in this new class to receive FDA approval for the treatment of the ‘wet’ form of macular degeneration. This drug – and the goal of other anti-angiogenesis drugs being tested – is to slow down or prevent the growth of the abnormal blood vessels.
- Vitamins: Vitamins C, E, beta carotene, zinc and copper have been shown to decrease the risk of vision loss in patients with intermediate to advanced dry AMD. Ask your eye doctor if these vitamin supplements will benefit you before taking them.
- Laser therapy: High-energy lights are used to destroy actively growing abnormal blood vessels.
- Photodynamic laser therapy: A two-step treatment in which a light sensitive drug is used to damage the abnormal blood vessels. A doctor injects the drug into the bloodstream to be absorbed by the abnormal blood vessels in the eye. The doctor then shines a cold laser into the eye to activate the drug, damaging the abnormal blood vessels.
- Low vision aids: Devices that have special lenses or electronic systems that produce enlarged images of nearby objects. They help people with partial vision make the most of their remaining vision.
Researchers are studying new treatments for AMD, such as those involved in the CATT study. The following treatments may soon be available, but are currently considered experimental:
- External beam radiotherapy: This procedure uses a low-dose radiation beam to prevent abnormal blood vessels from leaking. The blood vessels are treated at a layer of the eye that does not harm the retina.
- Submacular surgery: Surgery to remove the abnormal blood vessels or blood.
- Retinal translocation: A surgical procedure used to destroy abnormal blood vessels that are located directly under the center of the macula, where a laser beam cannot be placed safely. In the procedure, the macular center is rotated away from the abnormal blood vessels to a healthy area of the retina, thus preventing the formation of scar tissue and further damage to the retina. Once moved away from the abnormal blood vessels, a laser is used to treat the abnormal blood vessels.
- Gene transfer therapy: This technology involves inserting the desired genetic material into a patient’s own cells, which would then either guide the killing of abnormal cells or lead the growth of new cells to replace damaged cells. In the case of macular degeneration, this technology is investigating killing the cells that cause loss of vision (the epithelial cells) and/or replacing the light-capturing cells in the retina that are unable to be repaired once damaged.
What is the outlook for people with AMD?
Unfortunately, AMD can recur even after successful treatment. Various procedures, however, can slow the rate of vision loss and hopefully preserve some sight.
Resources For Patients
Cole Eye Institute Overview
Cleveland Clinic's Cole Eye Institute was designed by world-renowned architect Cesar Pelli, and is a significant architectural landmark, providing an ideal environment for research and top quality patient care, comfort and convenience. Opened in 1999, it handles more than 140,000 patient visits per year, treating adults and children with all ophthalmic conditions, performing basic eye care and eye surgery. Thousands of international patients travel to receive treatment, including all types of eye surgery, at the institute every year. A large team of researchers is committed to making breakthroughs in retinal disease. Eye surgery – ranging from cataract surgery to macular surgery – is performed daily by our world-class staff.
Many procedures developed at Cole Eye Institute have been adopted by ophthalmologists around the world, and the institute offers the largest hospital-based continuing medical education program in the United States. Our residency and fellowship programs are highly competitive and draw many applicants each year.
Cleveland Clinic is recognized in the U.S. and throughout the world for its expertise and care. Cleveland Clinic's Cole Eye Institute specializes in a range of options for treating eye diseases, such as eye surgery, retina disease, diabetic retinopathy and many others.
- Learn More About Cole Eye Institute
- Download our Free Retinal Disease Guide to learn more about symptoms, treatment options and our retina services
Resources For Physicians
Cleveland Clinic's Cole Eye Institute provides outstanding resources for clinicians and researchers seeking to treat such complex problems as macular degeneration, diabetic retinopathy, glaucoma, cataracts, retinal detachments, uveitis, strabismus and pediatric eye disorders, among many other diseases.
We offer one of the largest hospital-based continuing medical education programs in the United States and our Distinguished Lecture Series offers a forum for nationally known researchers to present highlights of their work. For more details, visit our Medical Education section.
- New England Journal of Medicine article discussing Year 1 CATT Study Results
- National Institutes of Health press release on Year 2 CATT Study Results
- Ophthalmology, an American Academy of Ophthalmology publication, article on Year 2 CATT Study Results
Ophthalmology Update is our publication, mailed out twice a year, that provides information for ophthalmologists about state-of-the-art diagnostic and management techniques and current research at The Cole Eye Institute. Read the latest issue, with full details of the CATT study and Year 1 impact.
Treating Age-Related Macular Degeneration
Macular degeneration is an eye disease that occurs when the small central portion of the retina, known as the macula, is damaged. The retina is the light-sensing nerve tissue at the back of the eye.
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