Retinopathy of prematurity (ROP) is a condition that affects premature infants. It is associated with local levels of low oxygenation and subsequent development of neovascularization (the growth of new blood vessels). This disease is only found in infants with immature, incompletely vascularized retinas.
During gestation, a baby's eye begins to develop at approximately 16 weeks. During this period, the blood vessels of the retinal vasculature begin to grow out from the optic nerve. As the blood vessels grow along the retina towards the periphery, they supply oxygen and nutrients to the developing retina. When the baby is carried to full term, retinal blood vessel growth is nearly complete and the retina continues to develop normally until it is complete (a few weeks to a month after birth). When a baby is born premature, the retinal blood vessels have not had the opportunity to complete the length of the retina and therefore deprive the peripheral retina of nutrients and oxygen. Scientists believe that the oxygen and nutrient starved portions of the retina signal to the other areas of the retina that nourishment is needed and subsequently, new blood vessels (neovascularization) begins toward the avascular regions. Unfortunately, these new blood vessels tend to be abnormal and leak blood and fluid onto the retina which can lead to retinal scarring and vision loss.
There are 5 stages of ROP:
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, 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.
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