Retinopathy of Prematurity
Retinopathy of Prematurity (ROP) is an eye disease of the retina that can occur in babies who are born prematurely. ROP results in the growth of abnormal blood vessels in the eye which can lead to blindness. The disease primarily affects both eyes. While the chances of developing the disease are higher in babies who are premature and weigh less, not all premature babies will have the disease.
This article identifies the prevalence of ROP, causes of ROP, symptoms of ROP, prevention of ROP, and treatment options for the eye disorder.
Retinopathy of Prematurity (ROP) is an eye disease that can occur in premature babies, primarily affecting those weighing 2.75 pounds (1,250 grams) or less and born before 31 weeks of gestation, according to the National Eye Institute. A full-term pregnancy has a gestation period of 38–42 weeks. The risk of being born with ROP increases as the weight of the infant decreases. ROP has the ICD 10 code H35.133. It usually affects both eyes and can even lead to blindness.
How many infants are affected by ROP?
Advances in medicine, particularly in neonatal care, mean that doctors and nurses are able to save smaller and more premature babies than ever before. About 28,000 of the nearly 4 million babies born in the U.S. each year weigh 2.75 pounds or less, with around 14,000 to 16,000 of these preterm infants developing ROP.
It is important to note that not all premature babies with a low birth weight develop ROP. In fact, 90% of cases are so mild that the infant fully recovers without treatment, as the condition clears up on its own and leaves no permanent damage. However, infants with a more severe form of the disease can experience impaired vision or blindness that does not spontaneously resolve. Each year in the United States, approximately 1,200 to 1,500 infants develop ROP severe enough to require treatment, and about 400 to 600 infants will become legally blind from Retinopathy of Prematurity.
Signs and Symptoms
Retinopathy of Prematurity is not easily detected and can only be diagnosed after birth. As it does not usually cause any signs or symptoms when it develops in a newborn, a pediatric eye specialist can detect early signs of ROP by examining the infant’s retinas.
Infants with Retinopathy of Prematurity are at a higher risk for developing certain eye problems when they get older. Eye problems associated with ROP include:
- Abnormal eye movements (“nystagmus”)
- Near-sightedness (“myopia”)
- Crossed eyes (“strabismus”)
- Retinal detachment
- Lazy eye (“amblyopia”)
What Are the Stages of Retinopathy of Prematurity?
ROP progression is classified into five stages that range from mild (stage 1) to severe (stage 5):
The first stage of ROP is characterized by mild growth of abnormal blood vessels. Most infants who develop Stage 1 ROP recover without any treatment.
Infants with Stage 2 ROP experience moderately abnormal blood vessel growth. Despite this, most infants will recover from Stage 2 ROP without any treatment and develop 20/20 vision.
Stage 3 of ROP is characterized by severe abnormal blood vessel growth (also referred to as plus disease) where vessels grow towards the center of the eye, instead of following their normal growth pattern along the surface of the retina. This growth pattern results in enlarged and twisted blood vessel formation. Infants with Stage 3 ROP require medical intervention to prevent retinal detachment.
An infant with Stage 4 ROP will experience partial detachment of the retina. Pressure from scarring and abnormal blood vessels gradually pull the retina away from the wall of the eye. To prevent the retina’s total detachment, vitreoretinal surgery may be required.
The final stage of ROP involves a completely detached retina. If left untreated, infants will experience severe visual impairment and may develop blindness.
Beyond low birth weight and premature birth, other factors also contribute to the development of ROP. These include immature lung development, anemia, respiratory problems, and slow weight gain.
Immature Lung Development and Oxygen Therapy
Premature babies often have immature lung development, which prevents the lungs from exchanging oxygen properly. To help these premature infants survive, hospitals often administer oxygen therapy. Unfortunately, exposure to high oxygen concentrations during the newborn period seems to increase the risk of ROP.
Thankfully, improved techniques allow medical professionals to monitor the use of supplemental oxygen. Modern techniques allow for the precise administration of oxygen to treat breathing problems while minimizing the risk of tissue damage relating to Retinopathy of Prematurity, meaning that exposure to oxygen is no longer a major risk factor for ROP development.
Other factors can also contribute to the development of ROP in infants, including:
- Respiratory distress syndrome
- Chronic lung disease
- Decreased hemoglobin concentration or anemia
- Blood transfusion
- Low APGAR score (general measurement of neonatal health)
ROP develops when abnormal blood vessels grow and spread throughout the retina. The retina is the inner layer of the eye that receives light and converts it into electrical pulses that are sent to the brain, where the pulses are used to produce visual input. ROP can result in visual impairment and blindness when abnormal blood vessel growth leads to scarring and detachment of the retina.
Abnormal Blood Vessels Growth
A number of complex factors can contribute to the development of ROP in utero. An infant’s eye begins to develop around 16 weeks of pregnancy, beginning with the blood vessels near the optic nerve (at the center of the retina) and expanding towards the edges of the retina. The proper development of blood vessels is essential for supplying blood and nutrients to the eye. The eye develops especially rapidly in the last 12 weeks of pregnancy. Infants who are not born prematurely have near-complete retinal blood vessel growth. However, infants born prematurely may not have developed adequate blood vessels to nourish the periphery of the retina. When this occurs, the edges of the retina begin to transmit signals to other areas for nourishment which causes abnormal new blood vessels to form. Abnormal blood vessels are fragile and can bleed easily, which can result in retinal scarring. As scars attempt to heal, they begin to shrink, which then pulls on the retina and can cause it to detach from the back of the eye. When the retina becomes detached, an ROP diagnosis can be provided.
Several preventative measures can be taken to reduce the risk of ROP development in infants, including:
- Prevention of premature birth
- Proper oxygen level monitoring for infants born prematurely
- Reducing the risk of infection
- Preventing anemia and blood transfusion
- Ensuring proper weight gain
Researchers are working on other strategies to prevent ROP, such as optimizing the way the infant’s body uses oxygen and curbing the risk of seizures, infection, anemia, and blood transfusions that may contribute to the development of retinopathy of prematurity.
Infants diagnosed with Stage 1 or Stage 2 ROP usually recover on their own and develop 20/20 vision without medical treatment. For infants experiencing more advanced stages (3, 4, or 5) of ROP, surgery and laser therapy can help to manage the disease and prevent worsening of the condition. Assistive devices, such as eSight can also help in enhancing central vision if other treatments are ineffective.
ROP Surgery and Injections
For later stages of ROP, corrective surgery may be used to stop the development of abnormal blood vessels in the retina. Since the treatment focuses on the peripheral retina with the aim of preserving the central retina, some peripheral or side vision may be lost.Laser surgery and injections can also help with moderate stages of ROP. Other treatment options include scleral buckling and vitrectomy, which can help Stage 5 cases of ROP where the retina has detached. Although treatment for ROP reduces the chances of vision loss, it does not guarantee the preservation of vision.