Retinopathy of Prematurity
What is Retinopathy of Prematurity?
Retinopathy of prematurity (ROP) is an eye disease that can occur in premature babies. ROP causes the growth of abnormal blood vessels in the newborn’s eye. Retinopathy of prematurity can lead to blindness.
ROP primarily affects infants who weigh 2¾ pounds or less at birth, according to the National Eye Institute, and who are born before 31 weeks of gestation. The smaller the infant is, the more likely he or she is to develop 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. In fact, about 28,000 of the nearly 4 million babies born in the U.S. each year weigh 2 ¾ pounds or less. About 14,000 to 16,000 of these “preemies” develop some degree of ROP.
Fortunately, about 90 percent of premature infants who develop ROP have a milder form of the disease and do not need treatment, as the condition clears up on its own and leaves no permanent damage. Those with a more severe form of the disease can develop impaired vision or even blindness. Each year, approximately 1200 to 1500 babies develop ROP severe enough to require treatment and about 400 to 600 infants will become legally blind from retinopathy of prematurity. It is important to note that not all premature infants develop retinopathy of prematurity.
ROP affects the light-sensitive tissue that lines the back of the eye, known as the retina. Light carries visual information about the world. Light enters the eye and strikes the retina, which converts the information into electrical pulses. The optic nerve carries these pulses to the brain, which converts the pulses into a visual image.
Abnormal Blood Vessel Growth
A complex network of tiny blood vessels transport oxygen- and nutrient-rich blood to the retina, which it requires to function. Retinopathy of prematurity can cause blood vessels to grow abnormally large and in random spots in the retina. The abnormal blood vessels can leak or bleed, which can scar the retina. The scars can shrink and pull on the retina, detaching it from the back of the eye. Because the retina is essential for sight, detaching it will cause blindness.
ROP also affects the pattern in which blood vessels grow in the retina. The eye starts to develop at about 16 weeks of pregnancy. Blood vessels near the optic nerve at the center of the retina develop first, and then gradually grow towards the edges of the retina. The eye develops rapidly in the last 12 weeks of pregnancy. When babies are born full-term, the growth of blood vessels in the retina is nearly complete. The blood vessels may not have reached the edges of the retina in premature babies, however, so those areas of light-sensitive tissue may not have received the oxygen- and nutrient-rich blood they needed to develop.
Scientists think that the edges of the retina, known as the periphery, in babies with ROP send out “signals” to other areas of the retina for nourishment. The body responds to these signals by building blood vessels, which tend to be abnormally weak and fragile. These abnormal blood vessels can leak and bleed, which can scar the retina.
Signs and Symptoms
ROP typically develops in both eyes. It is one of the most common causes of visual loss among children. The disease can lead to lifelong vision impairment – in severe cases, retinopathy of prematurity can even lead to blindness.
Retinopathy of prematurity does not usually cause any signs or symptoms when it develops in a newborn. Only an eye care professional can diagnose ROP.
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 retinal detachment, nearsightedness, glaucoma, strabismus or “crossed eyes,” and amblyopia or “lazy eye.” Eye care professionals can treat or control these complications of ROP.
Stages of Retinopathy of Prematurity
There are five stages of retinopathy of prematurity, ranging from mild (stage I) to severe (stage V):
Stage I — Characterized by mild growth of abnormal blood vessels that resolves on its own without further progression; many babies who develop stage I improve without treatment and eventually develop normal vision
Stage II — Moderately abnormal blood vessel growth that usually improves on its own and without treatment; many children with stage II ROP develop normal vision as they age
Stage III — Characterized by the growth of severely abnormal blood vessels; eye care professionals consider treatment to reduce the risk of retinal detachment in children who have stage III “plus disease,” which means the blood vessels are enlarged and twisted
Stage IV — Features a partially detached retina that occurs when bleeding and abnormal eyes tug at the retina until it pulls away from the wall of the eye
Stage V — The end stage of the disease when the retina detaches completely from the wall of the eye; left untreated, the infant can have severe visual impairment and potentially even blindness
Medical scientists are still working to reveal the risk factors for developing retinopathy of prematurity. It is clear that the condition occurs only in premature infants, and especially in those weighing less than 3 pounds at birth and born before 28 weeks gestation. Severe retinopathy of prematurity can occur in larger premature infants in countries that have less developed newborn care practices.
Immature Lung Development
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.
In fact, retinopathy of prematurity appeared suddenly in preterm infants born in the 1940s, when hospitals began administering supplemental oxygen in closed incubators to treat premature newborns with breathing problems. 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. Despite the advances in care and technology in neonatal intensive care units (NICUs), the incidence of ROP remains high as premature infants of lower birth weights survive more often than ever before.
It is important to note that the use of supplemental oxygen alone is not enough to cause ROP. Furthermore, researchers have not yet determined a “safe” level of oxygen in premature infants.
Various factors can increase the risk of ROP in premature infants. These factors include multiple episodes of an abnormally slow heart rate, known as bradycardia. Seizures, infection, anemia, and blood transfusions may also increase the risk of ROP, or may be more common in infants who are more premature, smaller, or more severely ill, as these infants are more likely to have numerous complications associated with being born prematurely. The lower the birth weight and the greater the medical complications a baby has, the greater the probability of developing retinopathy of prematurity.
Researchers are still working to understand the specific underlying mechanisms that increase the risk for ROP. Free radicals produced during chemical reactions inside the body may contribute to the risk. The accumulation of free radicals may damage or impair the function of many cells of the body. If so, antioxidants may provide some protection against free radicals to lower the risk of ROP.
Prevention of Retinopathy of Prematurity
Prevention of premature births is essential for preventing retinopathy of prematurity. Diagnosing the condition early and getting prompt treatment can help prevent long-term vision problems in premature babies. Controlling the administration of oxygen supplementation and using advanced procedures for oxygen supplementation may be able to reduce the development of ROP. 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.
Children with mild ROP do not require treatment. Those with advanced forms of retinopathy of prematurity may benefit from treatment that stops the development of abnormal blood vessels and the complications they cause, such as scarring, tugging the retina away from the wall of the eye, and blindness.
Surgery and Injections
Surgery stops the development of abnormal blood vessels by scarring the tissue enough that blood vessels cannot form there. Surgery focuses on scarring the periphery of the retina to spare central vision. Preserving the central retina in this way allows the eye to see straight ahead, distinguish color, read, and do other important tasks. Because it focuses on the peripheral retina, though, the patient may lose some amount of peripheral vision.
Laser surgery and injections are the most common types of surgery for moderate types of ROP. Other procedures, such as scleral buckling and vitrectomy, can help with an advanced case of ROP with a detached retina.
Low Vision Technology for Retinopathy of Prematurity
Many people with visual problems associated with retinopathy of prematurity benefit from using low vision aids. Vision loss and loss of visual acuity from retinopathy of prematurity respond well to the magnification offered by low vision aids, and they respond particularly well to advanced assistive eyewear technology without potential negative side effects from medical treatments. eSight is one type of advanced assistive eyewear technology that uses state-of-the-art cameras, smart algorithms and high resolution screens to create crystal clear, real-time images. These devices make seeing faces, reading, watching television or using a computer possible.
Furthermore, many successful eSight users live with retinopathy of prematurity, such as Jesse Johnson, who uses it to read newspapers and books at home, and to read menus when he’s at dinner with his family.
For those who are legally blind, eSight is clinically validated to enhance vision to up to 7 lines on a doctor’s eye chart. It has a leading edge camera, liquid lens, and high definition display powered by smart algorithms. The high-speed, high-resolution 21.5 MP camera captures and then projects real-time footage onto two OLED screens in front of the eyes.