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.
ROP, also known as retrolental fibroplasia or 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.
Who Is at Risk for ROP?
Premature infants are at risk for this condition, particularly those with low birth weight and low gestational age.
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.
How Is ROP Diagnosed?
ROP is generally diagnosed through clinical examination of premature patients at risk.
How Does Retinopathy of Prematurity Affect the Retina?
Ophthalmologists describe several stages of involvement of the retina:
- 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.
In addition to the stage of disease, the area of the retina affected also is important, and is delineated as Zone 1, 2, or 3. If the vessels of the retina are particularly engorged and tortuous (i.e., twisted), it is described as "Plus" disease.
Stage, zone, and presence or absence of plus disease are taken together to classify ROP as Type 1 or Type 2:
- In most cases, ROP resolves spontaneously as the infant grows and his/her retina develops.
- Some infants, however, develop Type 1 ROP and require treatment.
- 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.
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 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.
Treatment has been shown to decrease the progression of ROP, but in some infants, despite treatment, ROP progresses to cause permanent abnormalities in the eye.
Retinal detachments are usually treated surgically through vitrectomy or scleral buckle surgery:
- In scleral buckle surgery, a buckle (a piece of silicone rubber) 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. Laser may be applied during the surgery, and some cases of retinal detachment may require both vitrectomy and scleral buckle surgery.