Retinopathy of Prematurity (ROP) damages premature babies' retinas, the layer of light-sensitive cells lining the back of the eye. ROP usually occurs in both eyes, though one may be more severely affected.

The last 12 weeks of a full-term pregnancy are an especially active time for the growth of the eye. When a baby is born prematurely, blood vessels are not ready to supply blood to the retina. At birth, abnormal new blood vessels form and cause scarring or detachment of the retina. The condition is especially common in very small babies. It is more likely to occur at one or two pounds than at three pounds. Despite improved medical care, the disease is becoming more common because smaller and sicker infants are surviving. Supplemental oxygen given to premature babies may be part of the cause of ROP, but not the only factor, as once thought.

In severe cases, the retina may be extremely scarred and detached. Many cases get better without treatment and only a small number of children go blind. Freezing (cryotherapy) or laser treatments can prevent progression of the disease. Children with ROP are more likely to develop nearsightedness and amblyopia (lazy eye). Glasses, patching, and eye muscle surgery can help these associated problems. Follow-up exams of severely affected children should continue periodically.