Retinopathy of prematurity
Retinopathy of prematurity is a bilateral disorder of abnormal retinal vascularization in premature infants, especially those of lowest birth weight. Retinopathy of prematurity often regresses or heals but in the advanced stages it can lead to severe visual impairment or blindness.
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.
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 less than 1500 g or under 30 weeks gestation at birth. Because disease onset is usually at 32 to 34 weeks gestational age, screening begins at 31st week. Depending on the severity of the eye disease ophthalmologic examinations continue every 1 to 3 weeks until infants have growth of vessels into the periphery. Because significant retinopathy of prematurity is rare in appropriately managed infants weighing more than 1500 g at birth, alternative diagnoses should be considered in these infants.
Abnormal vessel growth often subsides spontaneously but, in about 4% of survivors weighing less than 1 kg at birth, progresses to produce retinal detachments and vision loss within 2 to 12 months after birth. 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 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. When disease 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.