Retinopathy of prematurity (ROP), previously known as retrolental fibroplasia, is a disorder of altered retinal vascular development seen predominantly in premature infants, and has been associated with a multitude of factors, most notably brief periods of excessive oxygen delivery, low birth weight, and postconceptual age (PCA).
Normal development of retinal vasculature occurs between 16th and 44th months PCA. In the fetus, developing blood vessels grow gradually from the macula toward the edges of the developing retina. In full-term newborns, this process is typically complete at birth. In the premature infant, development of retinal vessels is impaired and retarded. Blood vessels continue to pathologically grow after birth, and these growing vessels are at risk for vasoconstriction and subsequent hemorrhage, leading to disorganized neovascularization with fibrous tissue formation and scarring. Scarring can eventually lead to peeling away of the retinal network, resulting in retinal detachment. In most cases, ROP spontaneously regresses but about 10% of at-risk neonates develop significant visual impairment that may include bilateral blindness. The spectrum or stages of disease are classified as:
Stage 1—Mildly abnormal blood vessel growth.
Many children who develop stage 1 improve with no treatment and eventually develop normal vision.
Stage 2—Moderately abnormal blood vessel growth.
Many children who develop stage 2 improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
Stage 3—Severely abnormal blood vessel growth.
The abnormal blood vessels grow toward the center of the eye instead of following normal growth pattern along the surface of the retina. Some infants who develop stage 3 disease improve with no treatment and eventually develop normal vision. However, when infants have a certain degree of stage 3 and “plus disease” develops, treatment is considered. Plus disease means that the blood vessels of the retina have become enlarged and twisted, indicating worsening disease. Treatment provides a good chance of preventing retinal detachment.
Stage 4—Partially detached retina.
Stage 5—Completely detached retina.
ROP is a multifactorial disease and has classically been attributed to even brief periods of hyperoxia. The risk of ROP development from hyperoxia is of particular concern when anesthetizing preterm neonates, especially since administering supplemental oxygen during and after an anesthetic is so commonplace. Anesthetic management includes using the lowest possible oxygen concentration to maintain the SpO2 between 90% and 95%.
The concept of the role of oxygen in the development of ROP has undergone several changes with increased understanding of the disease. The diagnosis of ROP in neonates with cyanotic congenital heart disease compromised the belief that ROP was due solely to an increased partial pressure of oxygen in the retinal arteries in premature neonates. The current understanding is that supplemental oxygen alone is not the sole contributor for the development of ROP in at-risk neonates.