The Premature Eye

When a baby is born prematurely, the retina is only partially formed. The blood vessels have grown into the retina at the very back of the eye but not into the rest of the retina. The amount of undeveloped retina is proportional to the severity of prematurity. The closer that a premature baby is to full-term, the more normally developed is the retina. The greater the prematurity, the greater is the amount of undeveloped retina.

Two factors influence vision loss from ROP: the amount of retina that is undeveloped at the time of birth and the severity of the disease. The retina is divided into Zones 1, 2, and 3, and the severity of ROP is graded as Stage 1, 2, 3, 4, or 5.

The diagrams below show the zones of the premature retina. As the premature blood vessels grow from the back to the front of the eye, the amount of premature retina decreases. At full-term, the blood vessels extend to nearly the entire retina.