(Editor's Note: The following material is reprinted from a brochure and other literature provided by the Multi center Trial of Cryotherapy for Retinopathy of Prematurity (CRYOROP)).
About A Premature Baby's Eyes
The retina is the inner lining of the eyeball that receives light and turns it into visual messages that are sent to the brain. If one thinks of the eye as being like a camera, the retina functions as the film. Blood vessels that supply the retina are one of the last structures of the eye to mature, and have barely completed growing toward the front of the eye when a full term baby is born. This means that a premature infant's retina is still incompletely developed.
For reasons not yet fully understood by medical science, the blood vessels in the immature part of the retina may develop abnormally in some very premature infants. This disorder is called Retinopathy of Prematurity (abbreviated ROP). It is more likely to develop in the smallest infants who have had the most complications during their Newborn Intensive Care Unit stay. In spite of th best care medical science can provide, ROP still develops in certain infants.
When ROP develops, one of three different things can happen:
1) In the large majority (about 80%) of babies who develop ROP, the abnormal blood vessels will heal themselves completely during the first year of life.
2) In some babies the abnormal blood vessels heal only partially. In these infants nearsightedness (myopia) develops and glasses may be required early in life. These children may be more prone to developing lazy eye (amblyopia) or a wandering eye (strabismus). Infants who develop any of these conditions need to have regular eye examinations throughout childhood to assure the best possible vision. In some cases a scar may be left in the retina resulting in vision problems which are not entirely correctable with glasses or any other means; patients with these scars need lifelong ophthalmic care. The scars of incompletely healed ROP are referred to as Retrolental Fibroplasia (RLF), which may be mild or severe.
3) In the most severe cases, the retinal blood vessels continue developing abnormally and form sear tissue which can pull the retina loose from its normal position in the back of the eye (retinal detachment). This results in serious loss of vision and sometimes complete blindness. Fortunately, only a small percentage (about 5%) of babies with ROP develop the advanced changes of RLF.
Multicenter Trial of Cryotherapy for Retinopathy of Prematurity
The National Eye Institute is sponsoring a multicenter study of retinopathy of prematurity, a disease that can cause blindness in premature infants. The study will evaluate cryotherapy as a possible surgical treatment for the disease. There are 24 participating centers nationwide, which include over 70 hospitals.
Retinopathy of prematurity is a disease that can affect the retina of very small premature infants. Its exact cause is unknown and it appears to be unpreventable in some of the smallest and sickest premature infants. In this disease, abnormal blood vessels start growing in the part of the retina toward the front of the eye, and in some cases this leads to scar tissue formation and retinal detachment. fortunately, the disease usually undergoes a healing process, but it can lead to permanent blindness. It has been estimated that more than 500 infants a year are blinded by retinopathy of prematurity in the U.S. alone. At least 2,000 babies have significant damage to one or both eyes. These numbers are unfortunately increasing as survival rates for the smaller premature infants improve. Treatment to favorably influence the course of this disease is urgently needed.
It has been suggested that a surgical technique called cryotherapy may help prevent the severe cases of retinopathy of prematurity from going on to cause blindness. The technique of cryotherap is not itself new or experimental, and has been used effectively for a number of years in treating many different retinal diseases. For retinopathy of prematurity however, it is unproven and its safety unclear. Cryotherapy involves temporarily freezing part of the retina while it is still immature. It is believed that doing this at a relatively early stage of the disease may possibly halt the abnormal blood vessel growth.
The study chairman is Dr. Earl A. Palmer, at the Oregon Health Sciences University in Portland, Oregon. Study data will be gathered and statistically analyzed in Houston, Texas at the University of Texas School of Public Health under the direction of Dr. Robert J. Hardy. During the next two years, over 6,000 infants will be enrolled in this study, from which around 300 babies who are at greatest risk for becoming blind will be identified. With the informed consent of the parents, one eye of each infant will be randomly assigned to receive cryotherapy or not. Because there are enough reports of treatment failures or suspected harm from cryotherapy, no infant will receive the treatment to both eyes. This limits the risk of this unproven form of therapy to each infant.
Surgical results will primarily be evaluated by means of eye photographs at a photo-reading center in Portland, Oregon under the direction of Dr. Robert C Watzke. The entire study's results will be continously monitored both with respect to effectiveness and safety by an independent committee of medical and lay experts.
This national study has two goals: (1) to learn more about retinopathy of prematurity and to identify factors that relate to the severity of the disease, and (2) to test whether cryotherapy is a valid treatment. If cryotherapy proves to be safe and effective, it could become the treatment of choice for future premature infants who are stricken with this cruel disease.
Centers Selected For CRYO-ROP Study
*Louisville KY: University of Louisville School of Medicine
*Pittsburgh, PA: Oakland Pediatric Ophth
*Durham, NC: Duke University Medical Center
*Cincinnati, OH: Children's Hospital, Medical Center
*Baltimore, MD: Wilmer Eye Institute
*Indianapolis, IN: Indiana University
*Birmingham, AL: University of Alabama School of Medicine
*Nashville, TN: Vanderbilt University School of Medcine
*Miami, FL: University of Miami School of Medicine
*Atlanta, GA: The Emory Eye Center
*Washington, DC: Children's Hospital
*New Orleans, LA: Tulane Medical Center
*Salt Lake City, UT: University of Utah
*Chicago, IL: University of Illinois
*Portland, OR: Oregon Health Science Center
*Rochester, NY: University of Rochester
*Minneapolis, RUN: University of Minnesota
*Columbus, OH: Children's Hospital
*Sacramento, CA: University of California, Davies
*Charleston, SC: Medical University of South Carolina
*Philadelphia, PA: Children's Hospital
*Dallas, TX: Baylor Medical Plaza
*Royal Oak, MI: Associated Retinal Consultants
*San Antonio, TX: University of Texas Health Science Center
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