Retinopathy of Prematurity
What is retinopathy of prematurity (ROP)?
Babies who are born prematurely still have a growing retina. The retina usually finishes growing a few weeks to a month after birth in full term babies, but in premature babies the retina is still growing. During the course of this growth, the blood vessels that bring blood to the retina can begin to develop abnormally. This abnormal growth is called retinopathy of prematurity. Many factors interact to cause retinopathy of prematurity. We do not understand all of the causes at present. A number of research studies are taking place that will help us better understand this problem.
Which babies are more likely to develop ROP?
It does not seem that all babies born prematurely are at risk of developing ROP. The general rule is that those born earlier (more premature) and those weighing the least at birth are the most likely to develop ROP. The neonatologist will determine which children need an examination. Any babies weighing less than 1250 grams (2 pounds, 12 ounces) or born at less than 30 weeks of gestation are at greater risk of developing ROP. It is also thought that babies who are very sick at birth and who require oxygen might be at risk of developing ROP even if they weigh more than the above-mentioned limits and if they are older than noted above. These babies may also be examined for ROP.
Why are eye exams performed on premature babies?
The only way to determine if ROP is present is by examining the inside of the eye. The retina is examined and changes and abnormalities in the retina can be noted.
When are the first eye exams performed?
Nurses and neonatologists will determine which children are at risk for ROP and need an eye examination. The first examination usually takes place at about 4-6 weeks after birth, if the child is healthy enough to undergo the examination.
Who performs the eye exams?
Ophthalmologists trained in the care of ROP; therefore retina specialists or pediatric ophthalmologists usually perform this examination.
Where are the eye exams performed?
If the baby has been discharged from the hospital before the age of 4-6 weeks, the exams are performed in the ophthalmologist's office. In general, most of the premature babies are still in the hospital at the time of the first exam and the exam is performed at the bedside in the neonatal intensive care unit.
How are the eye exams performed?
The doctor performs the exam with the help of an assistant. The assistant helps hold the baby during the examination. The baby's eyes are dilated with eye drops prior to the examination. The doctor may use an instrument called an "eyelid speculum" to hold the eyelids open and another instrument called a "scleral depressor" to help hold and move the eye into different positions so that all of the retina can be inspected. An instrument called an "indirect ophthalmoscope" is used; it has a special lens that sends a bright light into the eye, enabling the doctor to examine the retina.
Is the eye exam uncomfortable for a premature baby?
A premature baby is very sensitive to any type of examination. An eye exam can be stressful to a premature baby, but the extreme importance of such an exam in preventing blindness has to be kept in mind. A well-trained doctor should be able to perform this exam quickly and with minimal discomfort to the baby. As with almost any exam, the baby will cry, but this is not an indication that the examination is causing pain, particularly since the baby usually calms down very quickly after the exam and returns to sleep or to feeding almost immediately. (The baby should not be fed just before the examination). After the exam, the baby's eyelids may be red or slightly swollen. The white part of the eyes can also appear red and, occasionally, there can be small dots of blood on the white part of the eyes. These are not signs of injury or damage. The eyes will return to the way they were before the exam; however, blood may take several weeks to disappear completely.
How often are the follow-up eye exams performed?
The follow-up exams are scheduled depending on the stage and the extent of ROP. Usually exams are performed every 1-4 weeks while the baby is in the hospital and then every 1-4 weeks once the baby leaves the hospital. Occasionally some babies' retinas grow slowly, and if no ROP is present they can be followed at longer intervals. Generally the eye exams are performed until the retina has fully developed. This can sometimes take several months.
What are the different stages of ROP?
A: Retinopathy of prematurity is classified according to the severity of the changes of the blood vessels and the region of the retina into which the vessels have grown. The severity is referred to as the "Stage" and the retinal regions as "Zones".
Stages are as follow:
The "immature vessels" stage actually occurs in all infants, and does not necessarily lead to ROP. Also, when ROP regresses (goes away), the vessels may go through this stage again until they complete their growth.
- Stage 1 is a mild abnormality of the retinal vessel growth and does not require treatment.
- Stage 2 is a moderate abnormality of the retinal vessel growth and also does not require treatment.
- Stage 3 is a severe abnormality of the retinal vessel growth in which the blood vessels grow toward the center of the eye instead of following their normal growth pattern along the surface of the retina. When a certain degree of Stage 3 is present and when "plus disease" develops, treatment is considered. "Plus disease" indicates that the blood vessels of the retina have become enlarged and twisted. This is an indication of worsening of the disease. Plus disease can occur with almost any stage and its presence alone is not sufficient to require treatment.
- Stage 4 involves a partial detachment of the retina.
- Stage 5 involves a complete detachment of the retina and has an extremely poor prognosis for the child to obtain any vision
What happens if the ROP does not go away?
Most of the time, Stages 1, 2, and even some Stage 3 cases may go away without treatment. In a small number of babies, for reasons not well understood as yet, ROP worsens and can develop into a sight-threatening condition. If this occurs treatment is usually recommended by the doctor.
What treatments are there for ROP?
Starting in the late 1980's, treatments became available for ROP. The first treatments for ROP were "cryotherapy" or freezing treatments. A freezing probe was held onto the outside of the eye to freeze the peripheral retina (side of the retina). This caused the ROP to go away in many cases, and reduced the chances of retinal detachments and blindness by about 50% as compared to babies who had no treatment. Not all babies responded favorably to this treatment.
More recently, lasers have been used for treatment of ROP, which appears to work better, but not all babies respond to this treatment either. Laser treatment is less painful, and causes fewer problems than the freezing treatments, but both treatments are accepted, and are still in use today.
The purpose of the treatment is to create scar tissue on the peripheral retina. This has been shown to eliminate ROP progression in many cases. The treated part of the retina will be scarred and will no longer work. The goal of the treatments is to save as much as possible of the central retina, where the best vision is located. Some of the peripheral retina and, therefore, some of the side vision will likely be lost after these treatments. It is important to keep in mind that the central retina, where the reading vision, straight ahead vision, and most of the color vision are located, is the most important part of the retina to save.
If the retina detaches due to ROP the child may need specialized surgical treatment. Despite the surgical treatment, children who develop a retinal detachment associated with ROP have a very poor visual prognosis.
How is the laser treatment done?
The laser treatment can be performed with the baby in the crib in the neonatal intensive care unit (NICU). The baby may be given medication to make it sleepy and comfortable. The baby's heart rate and breathing is monitored during the entire procedure. The laser beam is directed through the pupil to treat the side part of the retina. The procedure is similar to the examination with the addition of laser. The treatment usually takes 30-90 minutes per eye. Afterwards, the baby's eye may be red, and the eyelids may be red and a little swollen. Eyedrops or ointment are used for about one week. The redness and swelling usually goes away in a few days but may take a few weeks to completely disappear. A follow-up exam is usually performed 1-3 weeks after the laser treatment.
What are the risks?
Not all babies respond to the treatment, and the ROP may continue to worsen. Further treatments may be offered, either by more laser or, in some cases, surgery inside the eye. Bleeding inside the eye (vitreous hemorrhage), which is a potential complication of ROP, may occasionally follow the laser treatment. Vitreous hemorrhages do not cause damage to the eye, and usually clear up after several weeks. Scar tissue inside the eye, resulting from the disease process and/or treatment, may cause pulling on the retina that can lead to distortion or even detachments of the retina. Cataracts may form. Despite the treatment the child may develop a retinal detachment and lose most or all of their vision.
What happens if the laser treatment does not work?
The biggest concern, if the ROP laser treatments do not work to halt the scar tissue growth, is the development of retinal detachment.
Sometimes, only part of the retina detaches. If only the peripheral retina detaches, further treatments may not be performed, since these peripheral detachments may remain the same or go away without treatment.
If the center part of the retina or the entire retina detaches, then surgery may be attempted to try to reattach the retina. This surgery involves removing the scar tissue inside the eye to help the retina to reattach. Surgery is not recommended for distortion of the retina or for scar tissue that is not causing a detachment affecting the central vision.
What has to be done for the baby after the laser treatments are performed?
Eye drops or ointments are used for about 1 week. No further eye medications are usually required. Surgery inside the eye requires other medication regimens that depend on the type of surgery and on the individual surgeon.
What is the follow-up care after laser treatments?
Usually the eyes are examined after 1-3 weeks to see if they have responded to the treatment. If the eyes have responded to the laser treatment, no further treatments are required. The eyes may be examined at intervals of 2-6 weeks and then several months later to ensure that no further changes are occurring. If the eyes did not respond, further treatments might be suggested. These might include more laser or possibly surgery. It is important to keep in mind that any baby who has had ROP may develop retinal detachments later in life also. This is more likely if any scar tissue is present. Routine eye exams should be continued at regular intervals, usually yearly.
What is the long-term care?
Any premature baby, whether it has had ROP or not, has a higher chance of being nearsighted or farsighted, or of having "strabismus", which means that the eyes turn in or out. Eyes with strabismus may develop amblyopia, also called lazy eye. Some of these problems can be corrected with glasses. Even a very small baby may require glasses. If it needs glasses it is important that these be obtained, so that the visual part of the brain develops normally.
In general, any premature baby should be taken to a pediatric eye doctor, to possibly fit for glasses and to make sure that the eyes are straight, at about 3-6 months after the baby's due date. If glasses do not straighten the eyes, surgery on the eye muscles may be considered. It is important for the eyes to be straight during the early development periods so that normal growth of the visual part of the brain can occur and the best vision can be achieved.
Many premature babies have limited vision for reasons other than ROP. Limited brain development or damage to the brain from other causes can limit vision.
ROP, even if it becomes inactive and does not require treatment, can leave scar tissue inside the eye. This scar tissue can cause some problems, including pulling (traction) on the retina, which could result in a distorted retina or even a detachment of the retina.
Does oxygen administered to babies cause ROP?
This is a complicated question that does not have a definite answer yet. A number of studies are being undertaken to evaluate the possible association of oxygen and ROP. It was thought at one time that too much oxygen caused ROP. However, many very premature babies would not survive or would be retarded without oxygen. Now there are many advances in neonatal medicine which help immature lungs develop and work better, so less oxygen can be used for the premature babies. It is also thought that not enough oxygen could cause ROP. The answer is probably that a combination of factors, all of which are not yet understood, and oxygen being only one factor, cause ROP. These days, neonatalogists are trained to not use excessive oxygen, and chances are that with better understanding of ROP in the future, we will reduce the number of babies with this problem.
Do neonatal intensive care unit (NICU) lights worsen ROP?
Studies have shown no correlation between light exposure and the development of ROP. At present there does not seem to be a connection.
Do vitamins help ROP?
Several years ago, studies were done showing that large doses of vitamin E reduced the chances of worsening ROP. However, babies who received large doses of Vitamin E had many more medical problems, some of which were life-threatening. Thus, vitamin therapy is not currently recommended for ROP.