Retinopathy of Prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants.
ROP affects babies weighing about 2-3/4 pounds (1250 grams) or less at birth and that are born before 31 weeks of gestation (a full-term pregnancy has a gestation of 38-42 weeks).
The smaller a baby is at birth, the more likely that baby is to develop ROP. This disorder which usually develops in both eyes is one of the most common causes of visual loss in childhood and can lead to lifelong vision impairment and blindness.
Causes of Retinopathy of Prematurity
ROP occurs when abnormal blood vessels grow and spread throughout the retina, the tissue that lines the back of the eye.
These abnormal blood vessels are fragile and can leak, scarring the retina and pulling it out of position. This causes a retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in Retinopathy of Prematurity.
Several complex factors may be responsible for the development of ROP. The eye starts to develop at about 16 weeks of pregnancy, when the blood vessels of the retina begin to form at the optic nerve in the back of the eye. The blood vessels grow gradually toward the edges of the developing retina, supplying oxygen and nutrients.
During the last 12 weeks of a pregnancy, the eye develops rapidly. When a baby is born full-term, the retinal blood vessel growth is mostly complete (the retina usually finishes growing a few weeks to a month after birth). But if a baby is born prematurely, before these blood vessels have reached the edges of the retina, normal vessel growth may stop. The edges of the retina (the periphery) may not get enough oxygen and nutrients.
Scientists believe that the periphery of the retina then sends out signals to other areas of the retina for nourishment. As a result, new abnormal vessels begin to grow. These new blood vessels are fragile, weak, and can bleed, leading to retinal scarring. When these scars shrink, they pull on the retina, causing it to detach from the back of the eye.
Stages of Retinopathy of Prematurity
ROP is classified in five stages, ranging from mild (Stage I) to severe (Stage V)
- Stage I Mildly abnormal blood vessel growth. Many children who develop stage I improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
- Stage II Moderately abnormal blood vessel growth. Many children who develop stage II improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
- Stage III Severely abnormal blood vessel growth. The abnormal blood vessels grow toward the center of the eye, instead of following their normal growth pattern along the surface of the retina. Some infants who develop Stage III improve with no treatment and eventually develop normal vision. However, when infants have a certain degree of Stage III and plus disease develops, treatment is considered. Plus disease means that the blood vessels of the retina have become enlarged and twisted, indicating a worsening of the disease. Treatment at this point has a good chance of preventing retinal detachment.
- Stage IV Partially detached retina. Traction from the scar produced by bleeding or abnormal vessels pulls the retina away from the wall of the eye.
- Stage V Completely detached retina and the end stage of the disease. If the eye is left alone at this stage, the baby can have severe visual impairment and even blindness.
Most babies who develop Retinopathy of Prematurity have Stages I or II. However, in a small number of babies, ROP worsens, sometimes very rapidly. Untreated ROP threatens to destroy vision.
Retinopathy of Prematurity Treatment
The most effective proven treatments for Retinopathy of Prematurity are laser therapy or cryotherapy. Laser therapy burns away the periphery of the retina, which has no normal blood vessels.
With cryotherapy, physicians use an instrument that generates freezing temperatures to briefly touch spots on the surface of the eye that overlie the periphery of the retina. Both laser treatment and cryotherapy destroy the peripheral areas of the retina, slowing or reversing the abnormal growth of blood vessels. Unfortunately, the treatments also destroy some side vision. This is done to save the most important part of our sight the sharp, central vision we need for straight ahead activities such as reading, sewing, and driving.
Both laser treatments and cryotherapy are performed only on infants with advanced ROP, particularly Stage III with plus disease. Both treatments are considered invasive surgeries on the eye, and doctors don’t know the long-term side effects of each.
In the later stages of ROP, treatment options include:
Scleral buckle. This involves placing a silicone band around the eye and tightening it. This keeps the vitreous gel from pulling on the scar tissue and allows the retina to flatten back down onto the wall of the eye. Infants who have had a sclera buckle need to have the band removed months or years later, since the eye continues to grow, otherwise they will become nearsighted. Sclera buckles are usually performed on infants with Stage IV or V.
Vitrectomy. Vitrectomy involves removing the vitreous fluid and replacing it with a saline solution. After the vitreous has been removed, the scar tissue on the retina can be peeled back or cut away, allowing the retina to relax and lay back down against the eye wall. Vitrectomy is performed only at Stage V.
This information was developed by the National Eye Institute.