Development of ROP

As discussed earlier, growth of the blood supply to the retina begins at 16 weeks of gestation and proceeds until a little after a full term birth. If the retinal blood supply in the premature infant continues its development just as if the baby were still in the uterus, then retinopathy of prematurity does not develop.

ROP occurs when abnormal blood vessels and scar tissue form at the edge of the normal retinal blood supply.  The disease is caused by the abnormal retina's demand for oxygen.  As it has no blood supply, the abnormal retina is starved for the oxygen needed for normal function.  If the disease progresses to the stage requiring treatment, the initial treatment is to kill the abnormal retina and so eliminate its damaging demand for oxygen.

If retinopathy of prematurity develops, it usually appears between 35 and 45 weeks of conceptive age.  That is if the infant is born at 30 weeks gestation, and if retinopathy of prematurity were to occur, 

it would appear when the infant is between 5 and 15 weeks old.  In the majority of infants who develop ROP, the disease resolves spontaneously and the retinal blood supply develops normally.   If retinopathy of prematurity regresses, the disease has usually lasted about 15 weeks.
However, ROP can progress to a serious, and potentially blinding, eye problem which is estimated to result in the blindness of approximately 500 infants in the United States per year.