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Date: Sunday, April 14, 1996 FOR IMMEDIATE RELEASE Contact: Judith Stein or Susan Cahill (301)496-5248, JAS@B31.nei.nih.gov
Follow-up results from a study of premature babies with a potentially blinding condition confirm that a freezing treatment applied to their eyes helps save their sight. The follow-up results also give researchers more information about how well the babies can see in the years after cryotherapy, the freezing treatment.
"We have good evidence that this treatment significantly reduces the number of infants who are blinded by retinopathy of prematurity," said study chairman Earl A. Palmer, M.D., of Oregon Health Sciences University. "However, some patients may have an increased chance of having less-than-perfect vision after cryotherapy," he added.
The latest findings are from a 5 1/2-year follow-up study of 291 infants who had cryotherapy for the condition, called retinopathy of prematurity (ROP), between January 1986 and January 1988. The infants were in the multicenter trial of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP), which was sponsored by the National Eye Institute of the National Institutes of Health (NIH). Results of the follow-up study were published today in the April issue of the Archives of Ophthalmology.
Current estimated figures for the United States show that more than 4,000 premature babies weighing 3.3 pounds or less develop eye damage or vision loss from ROP each year. If cryotherapy were not available, 750 of the babies with the severe form of the disease would become legally blind each year, according to researchers' predictions. With widespread use of cryotherapy, a smaller number of babies, 400, become blind from the disease annually, researchers estimate. The CRYO-ROP study involved higher-risk babies who weighed only 2.75 pounds or less at birth and had the severe form of the disease.
ROP occurs when, for unknown reasons, blood vessels that feed parts of the retina grow in excess and become misshapen after birth. The retina is the light-sensing nerve tissue that lines the back of the eye and is crucial for normal vision. The abnormal blood vessels cause bleeding and scarring that can make the retina peel away from the back of the eye.
Doctors performing cryotherapy use a cryoprobe -- a hollow instrument filled with refrigerant -- to stop the growth of the abnormal blood vessels. They touch spots on the surface of the eye with the probe, which reaches freezing temperatures. The surface of the eye is not permanently harmed, but the freezing temperature destroys the outer edge of the retina, stopping the growth of the abnormal blood vessels.
While some babies become blind from ROP, others achieve adequate or better vision if left untreated. In the years after CRYO-ROP, researchers evaluated the babies' eyes that had been treated with cryotherapy and those that had not been treated to compare their vision and structure.
For the first several years, some of the children could not read a standard eye chart because they could not recognize letters or cooperate. Researchers used other methods to test the children's vision until they were almost 6 years old.
For the 5 1/2-year follow-up study, researchers were able to test 75 percent of the children using the standard eye chart. Vision of 20/40 or better was considered to be in the normal range, and children with vision of 20/200, the legal definition of blindness, or worse were considered blind. The study shows that 62 percent of the infants' eyes that were not treated with cryotherapy became blind, whereas 47 percent of treated eyes became blind. This difference is statistically significant.
The findings also suggest that cryotherapy might be associated with less-than-perfect vision. Twenty percent of untreated eyes now have vision of 20/40 or better, while 13 percent of treated eyes have vision in that range. This difference is not statistically significant; in addition, 25 percent of the children could not be tested at the 5 1/2-year follow-up. At the next follow-up, researchers will include the children whom they previously could not test.
Because cryotherapy was shown to be so effective in preventing blindness, the National Eye Institute sent a nationwide clinical alert to physicians who care for premature infants when the study's initial results became available in 1988. Since then, the treatment has become widely used.
"These results clearly favor cryotherapy for more severe cases of ROP, but we may want to be cautious about treating less severe ROP," said Carl Kupfer, M.D., director of the National Eye Institute. "If the milder form of this disease is left untreated, most of the children will have healthy eyes and good vision later on. Cryotherapy might worsen their visual acuity without providing any benefit," he added.
The researchers are preparing to perform another follow-up study of the children, who are now almost 10 years old. At that time, more of the children will have the skills required to take the standard eye chart test, and their visual systems will be more developed. Researchers will be able to investigate further the preliminary suggestion that cryotherapy, while effective in preventing blindness, might be associated with an increased chance of less-than-perfect vision.
The 5 1/2-year follow-up examination also showed that cryotherapy was associated with benefits other than blindness prevention in ROP. Children's eyes that had been treated had fewer of the abnormalities, such as cataract, often seen in severe cases of the condition. Many doctors now use lasers instead of cryoprobes to stop ROP progression. Controversy exists over whether eyes treated with lasers are more likely to develop cataract than are eyes treated with cryoprobes.
In another NIH-supported study, researchers estimated that appropriate screening and treatment of ROP in premature infants would save society between $38 million and $65 million a year in special education, disability, and other costs, and in lost productivity.
The National Eye Institute is the Federal government's lead agency for vision research, and supports more than 80 percent of such research conducted in the United States.
Cryotherapy For Retinopathy of Prematurity (CRYO-ROP) Participants List Alabama Frederick J. Elsas, M.D. Alabama Ophthalmology Associates, P.C. 1000 - 19th Street South Birmingham, Alabama 35205 Telephone: (205) 930-0700 California Alan M. Roth, M.D. Department of Ophthalmology University of California at Davis Medical Center 1603 Alhambra Boulevard Sacramento, California 95816 Telephone: (916) 734-6078 District of Columbia William S. Gilbert, M.D. Childrens Hospital National Medical Center Retina Group of Washington 5454 Wisconsin Avenue, Suite 1540 Chevy Chase, Maryland 20815 Telephone: (301) 656-8100 David Plotsky, M.D. 650 Pennsylvania Avenue, S.E. Suite 270 Washington, D.C. 20003 Telephone: (202) 544-1900 Florida R. Michael Siatkowski, M.D. Bascom Palmer Eye Institute University of Miami School of Medicine 900 N.W. 17th Street P.O. Box 016880 Miami, Florida 33136 Telephone: (305) 326-6019 Illinois Marilyn T. Miller, M.D. University of Illinois Eye and Ear Infirmary 1855 West Taylor Street, Room 1.44 Chicago, Illinois 60612 Telephone: (312) 996-7445 Indiana Forrest D. Ellis, M.D. Department of Ophthalmology Indiana University School of Medicine 702 Rotary Circle Indianapolis, Indiana 46202 Telephone: (317) 274-1214 Kentucky Charles C. Barr, M.D. Kentucky Lions Eye Research Institute University of Louisville 301 East Muhammad Ali Boulevard Louisville, Kentucky 40292 Telephone: (502) 852-5470 Louisiana Robert A. Gordon, M.D. Department of Ophthalmology Tulane University School of Medicine 1430 Tulane Avenue New Orleans, Louisiana 70112 Telephone: (504) 588-5804 Maryland Michael X. Repka, M.D. Wilmer Ophthalmological Institute The Johns Hopkins Medical Institutions Wilmer Building, Room B1-35 600 North Wolfe Street Baltimore, Maryland 21287-9009 Telephone: (410) 955-8314 Michigan John D. Baker, M.D. 2355 Monroe Boulevard Dearborn, Michigan 48124 Telephone: (313) 561-1777 Michael T. Trese, M.D. Associated Retinal Consultants, P.C. 3535 West Thirteen Mile Road, Room 632 Royal Oak, Michigan 48073 Telephone: (313) 288-2280 Minnesota C. Gail Summers, M.D. Department of Ophthalmology University of Minnesota Phillips-Wangensteen Bldg., 9-240 Box 493, 420 Delaware Street, S.E. Minneapolis, Minnesota 55455-0591 Telephone: (612) 625-4400 New York Dale L. Phelps, M.D. Box 651, Neonatology University of Rochester SOM 601 Elmwood Avenue Rochester, New York 14642 Telephone: (716) 275-5884 North Carolina Edward G. Buckley, M.D. Duke University Eye Center Box 3802 Durham, North Carolina 27710 Telephone: (919) 684-6084 Ohio Miles J. Burke, M.D. Department of Ophthalmology Childrens Hospital Medical Center Pavilion 2-80 3333 Burnet Avenue Cincinnati, Ohio 45229-3039 Telephone: (513) 559-4751 Gary L. Rogers, M.D. Don L. Bremer, M.D. Columbus Childrens Hospital (Office Address) 555 South 18th Street Columbus, Ohio 43205 Telephone: (614) 224-6222 Oregon Earl A. Palmer, M.D. Oregon Health Sciences University Casey Eye Institute 3375 S.W. Terwilliger Boulevard Portland, Oregon 97201-4197 Telephone: (503) 494-5945 Pennsylvania Graham E. Quinn, M.D. David B. Schaffer, M.D. Children's Hospital of Philadelphia Division of Pediatric Ophthalmology One Children's Center Philadelphia, Pennsylvania 19104 Telephone: (215) 590-2791 Kenneth P. Cheng, M.D. Pediatric Ophthalmology & Strabismus 3518 Fifth Avenue Pittsburgh, Pennsylvania 15213-3387 Telephone: (412) 682-6300 South Carolina Richard A. Saunders, M.D. Storm Eye Institute Medical University of South Carolina 171 Ashley Avenue Charleston, South Carolina 29425-2236 Telephone: (803) 792-2761 Tennessee Stephen S. Feman, M.D. Department of Ophthalmology Vanderbilt University Medical Center 8000 Medical Center East Nashville, Tennessee 37232-8808 Telephone: (615) 936-2020 Texas Rand Spencer, M.D. 7150 Greenville Ave., Suite 400 Dallas, Texas 75231 Telephone: (214) 821-4540 Wichard A. Van Heuven, M.D. Department of Ophthalmology University of Texas Health Science Center 7703 Floyd Curl Drive San Antonio, Texas 78284-6230 Telephone: (210) 567-8400 Utah Robert O. Hoffman, M.D. Department of Ophthalmology John Moran Eye Center 50 North Medical Drive Salt Lake City, Utah 84132 Telephone: (801) 581-4955 Resource Centers Chairman's Office Earl A. Palmer, M.D. Casey Eye Institute 3375 S.W. Terwilliger Boulevard Portland, Oregon 97201-4197 Telephone: (503) 494-5945 Coordinating Center Robert J. Hardy, Ph.D. School of Public Health University of Texas Health Science Center Coordinating Center for Clinical Trials 1200 Herman Pressler Street, Suite 801 Houston, Texas 77030 Telephone: (713) 792-4495 Ocular Pathology Center David J. Wilson, M.D. Casey Eye Institute 3375 S.W. Terwilliger Boulevard Portland, Oregon 97201-4197 Telephone: (503) 494-7881 Vision Center Velma Dobson, Ph.D. University of Arizona, SOM Dept. of Ophthalmology 1801 North Campbell Tucson, AZ 85719-3758 Telephone: (520) 321-3677