Retinopathy of Prematurity (ROP)
What Is Retinopathy of Prematurity?
Retinopathy of prematurity (ROP) is a disease of the retina that can occur in premature babies. The retina is the thin, light-sensitive tissue that lines the inside surface of the eye. Cells in the retina convert incoming light into electrical impulses. These electrical impulses are carried by the optic nerve to the brain, which finally interprets them as visual images. As an analogy, if the eye is a camera, then the retina is the film of the camera.
ROP, also known as retrolental fibroplasia (RLF), was first described in the mid-1900s. At that time, it was thought that the condition was related to the use of oxygen therapy in newborn, especially premature, babies. Since then, the role of supplemental oxygen in ROP has been disproven. While significant progress has been made into understanding the processes that lead to ROP, the precise mechanisms remain largely unknown.
The normal development of blood vessels in the retina (a process referred to as vascularization) is not completed until a baby reaches full term (40 weeks) in utero. In premature babies, the retina has not fully developed. If retinal vascularization completes outside the uterus (i.e., after the premature birth), the retinal vessels may stop growing, or they may grow abnormally. ROP occurs when these vessels develop in an abnormal way.
For more information for parents of children with ROP, visit FamilyConnect’s guide to ROP.
Who Is at Risk for ROP?
Premature infants are at risk for this condition, particularly those with low birth weight and low gestational age.
As a result, a 2013 consensus policy statement by the American Academy of Pediatrics, the American Academy of Ophthalmology, and the American Academy of Pediatric Ophthalmology and Strabismus on ROP recommends the screening of all infants born at less than 31 weeks gestational age; weighing less than, or equal to, 1500 grams at birth; or in whom the neonatal course, in the opinion of the neonatologist, was complicated. The consensus policy statement also clarifies the recommendations for follow-up exams and treatment.
What Are ROP Screening Examinations?
Experts perform screening examinations for ROP by clinically examining the baby, often in the neonatal intensive care unit, but also in the clinic after the baby is discharged home. This may involve placement of a thin metal speculum to keep the eyelids open. The doctor examines the retina using a scope on his or her head (called an indirect ophthalmoscope) and a handheld lens that focuses the image from the retina.
How Does Retinopathy of Prematurity Affect the Retina?
ROP is classified by the part of the retina affected (zone), the degree of involvement (stage), and the appearance of the blood vessels (presence or absence of “plus” disease).
- Zone 1 is the most posterior (or most central) retina.
- Zone 2 is the intermediate (between the posterior and peripheral) retina.
- Zone 3 involves the peripheral (or outer) retina.
- The retinal vessels begin to develop in zone 1 and then gradually grow outward to the retinal periphery until reaching zone 3; thus, zone 1 involvement is more severe than zone 3 involvement.
- Stage 1: There is a demarcation line between the retina that has achieved vascularization and the more peripheral retina (i.e., the outer edges) that has not yet been vascularized. This indicates incomplete development of the retinal blood vessels, and in most cases, these babies, with time, will complete normal development of the retinal vessels.
- Stage 2: The demarcation line is elevated like a ridge.
- Stage 3: There is development of abnormal vessels (called neovascularization), which are not healthy, are fragile, and are prone to leaking blood. In addition, these abnormal vessels are often associated with fibrous scar tissue that can contract over time, pulling the underlying retina away from its attachment to the eye, which ultimately results in a retinal detachment.
- Stage 4: Retinal detachment occurs. If it does not involve the central retina (called the macula) which is responsible for most detail vision, it is classified as stage 4a. If the macula is involved, then the ROP is stage 4b.
- Stage 5: Total retinal detachment, in which the retina in its entirety is detached.
Presence or Absence of “Plus” Disease
- Finally, if the vessels of the retina are particularly engorged and tortuous (i.e., twisted), it is described as “plus” disease. Clinicians report presence or absence of plus disease, based on their examinations.
In babies who do have ROP, zone, stage, and presence or absence of plus disease are taken together to classify ROP as mild ROP, Type 1 ROP, or Type 2 ROP.
- In most cases, ROP resolves spontaneously as the infant grows and his/her retina develops.
- Some infants, however, develop Type 1 or worse ROP and require treatment (see below).
- Type 2 ROP does not require treatment, but does require clinical monitoring. The frequency and length of monitoring depends upon the status of the retinal vascularization and ROP.
In some babies, the retinal vessels are not yet fully developed but no abnormalities are noted (i.e. there is no stage 1 or worse findings). This is classified as immature vascularization rather than ROP. ROP may develop at any time, however, until the vessels are fully developed, so these babies, as well as babies with ROP, are followed closely until the vascularization is complete.
Even premature babies without ROP, or premature babies whose ROP resolves or is treated, are at risk for other eye conditions, such as amblyopia, strabismus, refractive error, delayed maturation of the visual system, and other eye disease. As such, they should undergo eye exams as recommended by the eye doctor.
How Is ROP Treated?
When ROP requires treatment, as in Type 1 or worse ROP, the most common treatment is laser therapy to the immature retina. The goal of laser therapy is to prevent the progression of ROP and reverse the growth of abnormal blood vessels that may have developed. Previously, cryotherapy (cold therapy) was also administered, but this is rarely used at present. Laser treatment may be done with or without anesthesia and involves application of laser through the pupil to the retina. No incisions are required.
Laser has been shown to decrease the progression of ROP, but in some infants, despite appropriate laser treatment, ROP progresses and may require additional interventions or may cause unfavorable structural or visual outcomes.
More recently, studies suggest a role for the use of intraocular (within, or into, the eye) injection of a medication (Avastin or Lucentis) for treatment of some cases of ROP, either in lieu of, or in conjunction with, laser therapy. These medications inhibit a molecule called vascular endothelial growth factor (VEGF) which is thought to be implicated in the abnormal vascularization in ROP.
This treatment has been demonstrated to be effective, especially for zone 1 or posterior zone 2 Type 1 ROP, and further studies are ongoing to clarify the ideal timing, dosage, treatment regimen, indications, efficacy, safety, and subsequent followup regimen with this therapy.
This therapy has been shown to decrease the progression of ROP, but in some infants, despite appropriate treatment, ROP progresses and may require additional interventions or may cause unfavorable structural or visual outcomes.
Retinal detachments (stage 4 or 5 ROP) are usually treated surgically through vitrectomy or scleral buckle surgery:
- In scleral buckle surgery, a buckle (a silicone sponge, rubber, or hard plastic material) is sewn to the sclera (the coating of fibrous tissue that covers the white part of the eye) to indent it and relieve traction or pulling from the vitreous on the retina. This surgery is performed entirely outside the eye. The buckle remains in place after the conclusion of the surgery.
- In vitrectomy, the vitreous is removed to relieve traction or pulling from the vitreous on the retina. The vitreous is a jelly-like substance that fills the inside of the back part of the eye and is attached to the retina. In some cases, the lens of the eye may have to be removed as well. Laser may be applied during the surgery, and some cases of retinal detachment may require both vitrectomy and scleral buckle surgery.
ROP in Later Life
Individuals with ROP are considered to be at higher risk for developing certain eye problems later in life, such as retinal detachment, myopia (nearsightedness), strabismus (crossed eyes), amblyopia (lazy eye), and glaucoma. In many cases, these eye problems can be treated or controlled. Thus, it is important for patients with a history of ROP to have regular dilated eye examinations by an ophthalmologist even after the ROP has regressed.