Retinopathy of Prematurity (ROP) | Symptoms & Causes

About half of the estimated 28,000 premature babies born each year in the United States have some degree of retinopathy of prematurity. The fact that it’s fairly common doesn’t make hearing the diagnosis any easier. But the more you know about ROP and your child’s eyes, the less stressful the experience is likely to be for you and your family.

Think of your child’s eyes as a camera. The front of the eye has the lens, which focuses on an image, and the pupil, which works like a camera shutter to control how much light enters the eye. At the back of the eye is the retina: Like film in the camera, this layer of nerve tissue is necessary to record the information that’s coming in and allow the brain to “develop” it into an image.

When children are born early, the blood vessels that feed the retina usually haven’t finished growing. ROP occurs when these vessels actually stop growing for a time, then begin growing abnormally and randomly. The new vessels are fragile and can leak, leaving the retina scarred. In the worst-case scenario, the retina detaches (tears away from the back wall of the eye) and puts the baby at high risk of becoming blind.

To better understand your child’s condition, it helps to know the three most common ways doctors describe ROP: by zone, by stage and by the presence or absence of “plus disease.”

  • The zone indicates where the disease is located. Zone 1 is a small area at the heart of the retina (surrounding the central visual area, including the optic nerve); Zone 2 covers the middle of the retina; and Zone 3 runs along the retina’s outer edge. The lower the zone number, the more serious the ROP.
  • The stage describes how far the disease has progressed. Stage 1 has mildly abnormal vessel growth, while Stage 5 is “end stage” — the abnormal growth and scarring are so severe that the retina detaches.
  • Plus disease means that the blood vessels themselves are abnormally twisted and enlarged. A finding of plus disease or its warning signs (known as pre-plus disease) is a serious one, and has become very important in helping doctors decide when treatment is needed.


Who is at risk?

Premature babies are the number-one risk group for retinopathy of prematurity. In general, the smaller and more premature the infant, the more likely he or she is to develop ROP, and the more likely to need treatment.


Babies considered most at risk for ROP have:

  • a gestational age of 30 weeks or less, compared with 38 to 42 weeks for a full-term infant (“gestational age” means the amount of time since the baby was conceived)
  • a birth weight of 1,500 grams (3.3 pounds) or less, which is 2,000 grams (about 4.4 pounds) less than for a typical full-term infant

Other possible risk factors for ROP include:

  • anemia
  • infection
  • transfusions
  • breathing difficulties
  • heart disease
  • ethnicity (ROP occurs slightly more often in Caucasian children)

ROP has also been linked to supplemental oxygen, something often given to preemies. But excessive oxygen levels are largely a thing of the past, thanks to modern-day improvements in monitoring systems.

Causes of retinopathy of prematurity

Researchers are still working to understand the mechanism behind retinopathy of prematurity — that is, what causes the retinal vessels in many premature babies’ eyes stop growing, then begin growing abnormally.

Studies led by Children’s Hospital Boston ophthalmologist Lois Smith, MD, PhD, suggest that ROP might be caused by the early cutoff of chemicals that babies receive from their mother in the womb, including insulin-like growth factor I (IGF-I) and vascular endothelial growth factor (VEGF). However, it’s possible there are other chemicals are at play, and research is ongoing.

Signs and symptoms

Many of the signs of retinopathy of prematurity happen deep inside the eye, which means you won’t be able to see them just by looking at your child. Only an ophthalmologist (a doctor who specializes in caring for eyes) who is trained to recognize and treat ROP can spot these signs, using special instruments to examine your child’s retina.

The American Academy of Pediatrics has set ROP screening guidelines for all newborn intensive care units, and the vast majority of infants with ROP are identified through those exams.

An infant with severe ROP might develop visible complications, such as nystagmus (abnormal eye movements) and leukocoria (white pupils). However, these are also general signs of vision trouble — if your child has any of these, you should see an ophthalmologist right away.


Q: Do all babies born prematurely get ROP?

A: No. In about one out of two preemies, the blood vessels continue growing normally (although finishing the job a few weeks later than the original due date).

Q: How common is severe ROP?

A: Of the estimated 14,000 premature babies born with ROP each year in the U.S., about 1,100 to 1,500 (about 10 percent) develop disease severe enough to require medical treatment. About 400-600 infants become legally blind from ROP.

Q: Can ROP get better or heal on its own?

A: Yes. This is called “regression” of the disease, and usually happens in mild ROP (Stage 1 and 2). It can also happen in more severe ROP—but even after the abnormal blood vessels go away, there may be retinal scarring that needs to be watched closely.

Q: Does ROP always happen in both eyes?

A: Yes and no: While this disease typically affects both eyes, occasionally it’s more severe in one eye than the other. Rarely, doctors may need to treat just treat one eye.

Q: How accurate is ROP screening?

A: Retinal exams by a pediatric ophthalmologist can detect the disease with about 99 percent accuracy, according to the American Academy of Pediatrics, which sets the screening guidelines.

Q: Does a diagnosis of ROP mean my baby has to stay in the hospital longer?

A: ROP screening doesn’t begin until a premature infant is four to nine weeks old, which means your baby might even be discharged from the NICU before he’s due for his first screening exam. If he’s diagnosed with ROP while still in the NICU, though, you’ll likely be able to take him home on schedule. Your doctors will watch how his ROP progresses—and decide when to treat it—through follow-up exams.

Q: How is ROP treated?

A: Laser therapy or cryotherapy (freezing) can help slow or reverse the abnormal growth of blood vessels; in the most severe stages of ROP, eye surgery may be needed. There are no FDA-approved medications to treat ROP, though some drugs are now being studied.

Q: What are the possible complications of ROP?
About 10 percent of infants with retinopathy of prematurity will need medical treatment, such as laser therapy (photocoagulation). Not all babies respond to treatment, though, and if the ROP continues to worsen it can cause such complications as:

  • scarring and/or dragging of the retina
  • retinal detachment
  • bleeding inside the eye (vitreous hemorrhage)
  • cataracts
  • blindness

The other 90 percent of infants have a mild form of ROP, which usually resolves itself without treatment in the first few months of life. However, these children may be at higher risk for developing certain eye problems later in life, such as myopia (nearsightedness), strabismus (crossed eyes), amblyopia (lazy eye) and glaucoma.

Q: Can ROP be prevented?
Since the exact cause of retinopathy of prematurity isn’t known, the best prevention is prenatal care to reduce the likelihood of premature birth.

Although doctors can’t prevent ROP, they can help prevent its most harmful effects through careful screening and treatment.