The impact of low birth weight on the visual pathway.

Editorials The impact of low birth weight on the visual pathway It is well known that the survival of babies born prematurely has increased greatly in the recent past and that low birth weight carries a significant morbidity for ophthalmic problems. However, the impact of low birth weight on childhood vision impairment in epidemiological terms is largely unknown. The article in this issue of the BJO (p 9) by Crofts and colleagues is therefore particularly welcome. Using the Oxford Register of Early Childhood Impairment, these authors gathered information on all babies with severe vision impairment born in the 4 years commencing January 1984. We are told that this population is reasonably representative of the UK as a whole. Vision impairment was defined as an acuity of 6/18 or less in the better eye identified by 5 years of age. From this database the birthweight specific rate of severe vision loss was calculated. The overall rate of severe vision impairment was 1.25/1000 births, but those of birth weight less than 1500 g contributed to 17.5% of the cohort and for this group the rate was 26 times that for babies of 2500–3499 g birth weight. The prevalence of associated impairments was high for all birth weights (60%), but highest for those under 1500 g (72%), decreasing with increasing birth weight to 44% for those over 3500 g. The time of origin of the disorder was estimated, as best as possible, according to three major categories—prenatal, perinatal, and postnatal, and each of these contained 60%, 24%, and 10% respectively (5% were unclassifiable). Thus, 84% of childhood vision impairment has its origins at birth or before, and once the perinatal period has passed, from the vision impairment point of view, the visual pathway is more likely than not to remain unscathed. The aetiological front runner was cortical vision impairment which accounted for 36% of all childhood vision impairment, and was followed by optic atrophy (13%) and cataract (10%), with nystagmus, retinal dystrophy, and retinopathy of prematurity (ROP) all accounting for 6% each. Mindful that most childhood vision impairment aVects parts of the visual pathway other than the eye, significant reduction of childhood vision impairment in the future has to come from preventing neurological prenatal and perinatal maldevelopment and/or damage. It is of interest that ROP accounts for such a small proportion of severe vision impairment in this low birthweight population, particularly as this …