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The Oxford Register of Early Childhood Impairment was set up in 1984 to collect information about children born in four counties of central England with severe visual impairment, cerebral palsy, or sensorineural deafness. Data have recently been published about children with severe visual impairment born in the four years 1984–87 (Crofts and colleagues; British Journal of Ophthalmology 1998;82:9–13; also editorialBritish Journal of Ophthalmology1998;82:1–2).
There were 132 416 live births during the study period and 166 children (1.25/1000 live births) had severe visual impairment (acuity in better eye 6/18 or less) by the age of 5 years. The rate was 26/1000 for 1118 children with birthweight below 1500 g, 3.6/1000 at birthweights 1500–2499 g, 1.0/1000 at 2500–3499 g, and 0.7/1000 at 3500 g and over.
Children with very low birthweight constituted 0.8% of all live births and 17.5% of those with severe visual impairment. The visual impairment was considered to be of prenatal or perinatal origin in 84% of all visually impaired children, and in 90% of those with very low birthweight, but it was considered perinatal in most very low birthweight children and prenatal in most of those with higher birthweight.
The most common cause was cortical visual impairment, which occurred in 60 children (36%) and was thought to be of prenatal origin in 27, perinatal in 23, and postnatal in 10. Only nine children had retinopathy of prematurity. Other causes were optic atrophy (21), cataract (16), congenital nystagmus (10), and several less common diagnoses. Associated motor, sensory, or developmental impairments were present in 72% of the very low birthweight visually impaired children and 54% of those who weighed more than 2500 g at birth.
Cerebral ischaemia is a more important cause of visual impairment in very low birthweight babies than is retinopathy of prematurity (ROP), at least in the UK. Fielder, in his editorial, however, points out that ROP is increasing in middle income countries such as those in Latin America and eastern Europe where neonatal care is such that more preterm babies are surviving but more are getting ROP. Nevertheless, two thirds of the children with severe visual impairment in this study weighed more than 2500 g at birth. Attempts to reduce the burden of visual impairment in children in developed countries will need to address the problems of genetic and other prenatal causes, and cerebral ischaemia.