The inner retinal blood vessels start growing about midpregnancy, but the retina is not fully vascularized until term. Retinopathy of prematurity (ROP) results if these vessels continue their growth in an abnormal pattern, forming a ridge of tissue between the vascularized central retina and the nonvascularized peripheral retina. In severe retinopathy of prematurity, these new vessels invade the vitreous. Sometimes the entire vasculature of the eye becomes engorged (plus disease).
Susceptibility to retinopathy of prematurity correlates with the proportion of retina that remains avascular at birth. In neonates weighing < 1 kg at birth, retinopathy of prematurity occurs in 47 to 80%, and severe retinopathy of prematurity occurs in 21 to 43%. The percentage is higher when many medical complications exist (eg, infection, intraventricular hemorrhage, bronchopulmonary dysplasia). Excessive (especially prolonged) oxygen therapy increases the risk. However, supplemental oxygen is often needed to adequately oxygenate the infant even though a safe level and duration of oxygen therapy have not been determined.
Diagnosis of retinopathy of prematurity is made by ophthalmoscopic examination, done by an ophthalmologist, which shows a line of demarcation and a ridge in mild cases and proliferation of retinal vessels in more severe cases.
Screening ophthalmoscopy is done in all infants weighing < 1500 g or < 30 weeks gestation at birth. Because disease onset is usually at 32 to 34 weeks gestational age, screening begins at 31 weeks. Ophthalmologic examinations continue every 1 to 3 weeks (depending on the severity of the eye disease) until infants have growth of vessels into the periphery (equivalent to term). Because significant retinopathy of prematurity is rare in appropriately managed infants weighing > 1500 g at birth, alternative diagnoses should be considered in these infants (eg, familial exudative retinopathy, Norrie disease).
Abnormal vessel growth often subsides spontaneously but, in about 4% of survivors weighing < 1 kg at birth, it progresses to produce retinal detachments and vision loss within 2 to 12 months postpartum. Children with healed retinopathy of prematurity have a higher incidence of myopia, strabismus, and amblyopia. A few children with moderate, healed retinopathy of prematurity are left with cicatricial scars (eg, dragged retina or retinal folds) and are at risk of retinal detachments later in life; rarely, glaucoma and cataracts can also occur.
In severe retinopathy of prematurity, laser photocoagulation to ablate the peripheral avascular retina reduces the incidence of retinal fold and detachment. Retinal vascularization must be followed at 1- to 2-week intervals until the vessels have matured sufficiently. If retinal detachments occur in infancy, scleral buckling surgery or vitrectomy with lensectomy may be considered, but these procedures are late rescue efforts with low benefit.
Patients with residual scarring should be followed at least annually for life. Treatment of amblyopia and refractive errors in the first year optimizes vision. Infants with total retinal detachments should be monitored for secondary glaucoma and poor eye growth and referred to intervention programs for the visually impaired.
Bevacizumab is an antivascular endothelial growth factor monoclonal antibody that can stop the progression of retinopathy of prematurity. Compared to laser therapy, bevacizumab has a lower rate of recurrence and fewer structural abnormalities in select cases (1). When retinopathy did recur, it recurred months later; long-term ophthalmology follow-up is required. Concerns regarding systemic absorption and possible infection coupled with the need for optimal dose and timing of follow-up are reasons why this drug has remained a 2nd-line therapy that can be used to treat severe disease or in conjunction with laser therapy.
Retinopathy of prematurity (ROP) typically develops in infants weighing < 1500 g and < 30 weeks gestation at birth, particularly those who had serious medical complications or who received excessive and/or prolonged oxygen therapy.
Risk increases with increasing prematurity.
Most cases subside spontaneously, but a small number develop retinal detachment and vision loss 2 to 12 months postpartum.
Screen at-risk infants by ophthalmoscopic examination (done by an ophthalmologist) beginning at 31 weeks gestation.
Treat severe ROP using laser photocoagulation or bevacizumab.
Minimize use of supplemental oxygen after premature birth.