Retinopathy of prematurity is a disease of the developing retinal vasculature that occurs in premature infants and is a leading cause of childhood blindness. The pathogenesis of this disorder is controversial but is believed to be environmental. High levels of inspired oxygen and ambient-light exposure cause an increase in free radicals in the retina, which may increase the incidence of retinopathy in premature infants. The effect of light on this disease has been debated for many years. Reynolds and colleagues performed a prospective, randomized, multicenter study to assess the effect of ambient light on the incidence of retinopathy in premature infants.
The study originally included 409 infants who had a birth weight of less than 1,251 g (2 lb, 12 oz), a gestational age at birth of less than 31 weeks and admission to a neonatal intensive care unit within 24 hours of birth. Children with a lethal congenital anomaly or a major congenital abnormality of one or both eyes were excluded from the study. The newborns were randomly assigned to a control group or a group that received light-reducing goggles within 24 hours after birth. The goggles reduced exposure to visible light by 97 percent and to ultraviolet light by 100 percent. Infants in the control group were exposed to the usual amount of light in the neonatal intensive care unit. The infants in the treatment group wore the goggles until 31 weeks after conception or four weeks after birth, whichever was longer. This length of time was chosen so that the goggles would be removed before it became necessary to identify children who had developed severe eye disease and would require surgical intervention.
After the goggles were removed, all infants had an initial ophthalmologic examination within seven days. They were then examined biweekly until their eyes were fully vascularized or, if retinopathy developed, until they reached 44 weeks' postconception age. A final ophthalmologic examination was performed on all infants six months after term. The ophthalmologists were blinded to treatment-group assignment.
During the study period, 46 infants died and two infants were lost to follow-up, leaving 188 infants in the treatment group and 173 in the control group. The baseline characteristics of both groups were essentially the same. The goggles were worn a median of 28 days. The mean light level measured adjacent to the infants' faces was 447 lux for the control group and 399 lux for the treatment group. There were 102 infants (54 percent) with confirmed retinopathy in the treatment group and 100 infants (58 percent) with confirmed retinopathy in the control group. At the six-month examination, myopia was diagnosed in 31 infants (19 percent) in the treatment group and 28 infants (19 percent) in the control group. All other ocular findings were similar between the two groups at the six-month visit.
The authors conclude that reduction in ambient-light exposure in the neonatal intensive care unit does not reduce the frequency of retinopathy of prematurity in newborns at high risk for this disorder.