Background The WHO's Vision 2020 global initiative against blindness, launched in 2000, prioritises children. Progress has been hampered by the global paucity of epidemiological data about childhood visual disability. The British Childhood Visual Impairment and Blindness Study 2 (BCVIS2) was undertaken to address this evidence gap. Methods UK-wide prospective population-based observational study of all those aged under 18 years newly diagnosed with visual impairment or blindness between Oct 1, 2015 and Nov 1 2016. Eligible children were notified simultaneously but independently by their managing ophthalmologists and paediatricians via the two national active surveillance schemes, the British Ophthalmic and Paediatric Surveillance Units. Standardised detailed data were collected at diagnosis and one year later. Incidence estimates and relative rates by key sociodemographic factors were calculated. Descriptive analyses were undertaken of underlying ophthalmic disorders and nonophthalmic comorbidities. FindingsOf 784 cases, 72% had additional non-ophthalmic impairments/disorders and 4% died within the year. Annual incidence was highest in the first year of life, 5•2 per 10,000 (95% CI 4•7-5•7) with cumulative incidence by 18 years of 10•0 per 10,000 (95% CI 9•4 to 10•8). Rates were higher for those from any ethnic minority group, the lowest quintile of socio-economic status, born preterm or with low birthweight. Only 44% had a single ophthalmic condition: disorders of the brain/visual pathways affected 48% overall. Prenatal or perinatal aetiological factors accounted for 84% of all conditions. InterpretationBCVIS2 provides a contemporary snapshot of the heterogeneity, multi-morbidity and vulnerability associated with childhood visual disability in a high income country, and the arising complex needs. These findings will facilitate developing and delivering healthcare and planning interventional research. They highlight the importance of including childhood visual disability as a sentinel event and metric in global child health initiatives.

Four families, each with two individuals affected by Rett Syndrome (RS), were analysed using restriction fragment length polymorphisms and microsatellite markers from the X chromosome. In two of the families, X-linked dominant inheritance of the RS defect from a germinally mosaic mother could be assumed. Therefore, maternal X chromosome markers showing discordant inheritance were used to exclude regions of the X chromosome as locations of the RS gene. Much of the short arm could be excluded, including regions containing three candidate genes, OTC, synapsin 1 and synaptophysin. Although most of the long arm was inherited in common it was possible to exclude a centromeric region. Inheritance of X chromosome markers is also presented for two families with affected aunt-niece pairs, one of which has not been previously studied at the DNA level.

Childhood visual impairment confers significant potential adversity on the individual, their family, and on wider society. 1,2 To address this at societal and individual levels, primary (preventing blinding disease from occurring), secondary (treatment of established disease to reduce negative impact), and tertiary prevention approaches are required. [3][4][5] Tertiary prevention approaches comprise interventions that mitigate the impact of established visual disability or associated disorders on the life of the child and the adult they become. These interventions may be simple, such as the provision of low vision aids, or more complex, such as the provision of parenting support, or the development of individualized 'packages' of multidisciplinary care for the additional physical, educational, psychological, and social developmental needs of the affected child. 6 In recognition of the high burden of the numerous developmental and non-ophthalmic disorders that coexist in children with impaired vision, multidisciplinary assessment of children newly diagnosed with visual disability is advocated. 1,3,7 Almost two decades ago, the British Childhood Visual Impairment and Blindness Study (BCVIS; 2003) confirmed that in the UK most children newly diagnosed with severe visual impairment and blindness (SVIBL; vision worse than 1.0 logMAR [logarithm of the minimum angle of

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