Aim To explore and describe trends in the principal disorders/conditions (‘cause’) for severe sight impairment (SSI) (blind) and sight impairment (SI) (partial sight) certification in children in England and Wales since 1999.
Methods We obtained certification data for SI and SSI from a national database for all individuals aged 16 years or less at the time of certification in England and Wales for the years 1999/2000 and for the years 2007/2008–2009/2010.
Results In total, there were 861 certifications in the year 1999/2000, rising to 1040 certifications in 2009/2010. The commonest single causes of SSI certification in 1999/2000 were cerebral visual impairment (23.2%) and optic nerve disorders (23.2%). The commonest single causes of SI certification in the same year comprised nystagmus (16.7%) and optic nerve disorders (15.5%). Cerebral visual impairment was the commonest single cause of SSI in children in England and Wales annually between 2007/2008 and 2009/2010 accounting for 21%–31% of certifications. The commonest causes of SI certification in 2009/2010 were congenital globe anomalies (18.4%) and retinal dystrophy (16.6%). The proportion of SI and SSI due to optic nerve disorders has decreased since 1999/2000.
Conclusions Our findings suggest that in England and Wales, cerebral visual impairment is now the commonest cause of paediatric SSI certification and hereditary retinal dystrophy and congenital globe anomalies are the commonest causes of SI certification.
- Child health (paediatrics)
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The prevention of sight loss in children is considered a high priority within WHO's VISION 2020—The Right to Sight programme.1 Nearly six children per 10 000 children born in the UK will be severely sight impaired by their sixteenth bithday.2 The VISION 2020 target for severe visual loss in children is to reduce the global prevalence of childhood blindness from 0.75 to 0.4 per 1000 children by addressing known avoidable causes.1
In England and Wales, between 1930 and 2003, registration as blind or partially sighted was initiated by completion of a BD8 form by the examining ophthalmologist. In 2005 in England and 2007 in Wales, the Certificate of Vision Impairment (CVI) officially replaced the BD8 certificate and is now the form used to formally certify someone as sight impaired/partially sighted (SI) or severely sight impaired/blind (SSI). This form also acts as the trigger to local councils to place individuals on the registers of blind or partially sighted people should they so wish.3 An adapted version especially for children was made available by the Royal College of Ophthalmologists with an extended taxonomy for provision of more detailed data on diagnosis or ‘causes’ in recognition of the limitations of the classification used in the original BD8 with respect to children. Although certification is not a statutory requirement, formal recognition of visual impairment is strongly encouraged as it conveys certain benefits for the patient and is often used as a way to access social service provisions.3 Based on a national certification database, the aim of this study is to provide a comparative analysis of the main causes of paediatric SSI and SI certification in 1999/2000 and annually for the years 2007/2008–2009/2010. There have been few recent reports on the causes of paediatric blind and partial sight certification in England and Wales and no assessments have been performed since the implemented change in certification form.
We previously reported an increasing trend in the numbers of children registered with SSI (blindness) and SI (partial sight) over this period and this study aims to look at diagnoses/causes reported and whether and how these have changed.4
Causal data were derived from all BD8 and CVI forms for the years 1999/2000 and 2007/2008–2009/2010 for England and Wales. We examined only certifications of individuals who were aged 16 years or less at the time of certification. The methodology of data acquisition has been described previously.5 ,6 Briefly, the BD8 or CVI form is completed by a consultant ophthalmologist who establishes a patient's eligibility for certification as either SI or SSI. The completed certificate is then forwarded to the local Social Services Department (SSD) which offers registration. If the person is not already known to social services as someone with needs arising from his or her visual impairment, the CVI is a referral for a social care assessment, leading to the offer of rehabilitation support. SSDs are mandated to maintain a register of blind and partially sighted people, so once the CVI is received, the local authority adds each patient to the SSI or SI register. The CVI forms also provide anonymous epidemiological data including the cause(s) of visual impairment and the age of the person at certification. As part of the registration process (see online supplementary figure S1), these data are sent to the Certifications Office, Moorfields Eye Hospital, for entry onto a database and are coded via the International Classification of Disease (ICD-9) to facilitate the analysis with earlier datasets. There is no legal definition of partial sight but guidance is provided within the certificate guidelines for completion. It is important to note that people are recommended for certification for irreversible loss of vision and that the certification is voluntary and with no statutory requirement for it to be offered. The Royal College of Ophthalmologists considers it good practice to offer certification to all patients who are eligible.7
Online supplementary figure S2 illustrates the method of main cause and multiple cause designation for each certified individual. Where no main cause was completed this was designated as unknown.
Table 1 illustrates the total number of children certified annually for the study years and the total number of children with a main diagnosis and with multiple diagnoses.
In total, there were 861 certifications in the year 1999/2000 and 1084 in 2007/2008. Figure 1 illustrates the most common causes of visual impairment (SI and SSI) between 1999/2000 and 2009/2010. Table 2 highlights a breakdown of the main causes of paediatric visual impairment (SI and SSI) certification for each of the study years. Excluding certifications where diagnosis was not reported /‘not identified’, the commonest single cause of SSI certification in children in the year 1999/2000 was cerebral visual impairment (23.2%) and optic nerve disorders (23.2%) (table 3). The commonest single cause of SI certification comprised nystagmus (16.7%) and optic nerve disorders (15.5%) (table 4). In 2007/2008, the commonest single cause of SSI certification was cerebral visual impairment (23.5%) and the commonest single cause of SI certification was congenital ocular anomaly (16.3%) and hereditary retinal dystrophy (15.7%).
The BD8 and CVI differ in how diagnosis is captured which has resulted in a much higher proportion of CVI certifications being attributed to multiple pathology than was found for BD8 certifications. For BD8s, typically less than 3% of all certifications were attributed to multiple pathologies but for CVIs, current figures suggest a rate between 7% and 17%.
The proportion of multiple listed causes has increased from <2% for SI and SSI in 1990/2000 to between 12%–16% of SSI and 8%–14% of SI certifications annually between 2007/2008 and 2009/2010.
In total, there were 1088 certifications in 2008/2009 and 1040 certifications in 2009/2010. Cerebral visual impairment was the commonest single cause of SSI certification for both years, comprising 21% and 29.3%, respectively. Similar to 2007/2008, the commonest single cause of SI certification was retinal dystrophy, comprising 14.5% and 16.6% in 2008/2009 and 2009/2010, respectively, and congenital ocular anomaly comprising 11.7% in 2008/2009 and 18.4% in 2009/2010 (table 4).
The aim of this paper is to provide an up to date analysis of the diagnoses reported as causes of SSI and SI certification in children aged 16 or less in England and Wales and to comment on the principal reason for certification over the last 10 years. The findings should be interpreted in the context of several limitations. Not all eligible individuals are certified and the certification and registration process with social services has been criticised in the past.8 However, a recent (though performed before the change from BD8 to CVI) national study of childhood blindness highlighted that within a year of diagnosis, certification of SSI had been completed, was in progress or had been offered to the parents of most of the eligible children demonstrating recently achieved improvements in ascertainment and completeness of reporting.9 SI and SSI may commonly be associated with other disabilty.2 ,10 From the data presented here, however, we are unable to comment on the prevalence coexisting physical or systemic disability.
Including multiple causes for certification, cerebral visual impairment (31.4%) and hereditary retinal disorders (16.3%) were common causes of blindness in children in England and Wales in 2009/2010, with this proportion steadily increasing since 1999/2000. Cerebral visual impairment may have increased simply through better understanding and recognition of the condition or there may be a true increase due to the improved survival of extremely premature infants who are more vulnerable to cerebral visual loss.2 In the developed world, cerebral visual impairment is the commonest cause of blindness.1 ,2 ,11 Contemporary estimates from the Oxford register in England found that cerebral visual impairment is a cause of visual impairment in up to 51% of cases, increasing to 87% for severe visual impariment.12 Rahi using surveillance by ophthalmologists and paediatricians determined that cerebral visual impairment alone was the cause of visual impairment in 48% of children and a 10-year retrospective analysis revealed that cerebral visual impairment and optic nerve disorders accounted for 43% of visually impaired children.11 ,13 Similarly, among children attending blind schools in the USA, the leading cause for blindness was cerebral visual impairment (up to 20%).10
Retinopathy of prematurity (ROP) is an uncommon cause of SI and SSI certification in England and Wales (<4%) compared with a higher rate of severe disease in developing countries (up to 23%).14 ,15 This is largely due to high quality neonatal intensive care, and well-established screening and treatment programmes for premature babies in the UK.16 Our findings support previous studies demonstrating a low prevalence of blinding ROP in highly industrialised nations15 ,17 and re-emphasises findings from the Oxford registry which demonstrated a significantly reduced risk of visual impairment associated with prematurity and low birth weight in the 1980s and 1990s.12
In general, treatable causes of blindness such as ROP, infection and congenital cataract have become less common due to improvements in detection and management over recent decades.18 ,19 Conversely, untreatable disorders such as hereditary retinal dystrophies have become more common in recent years. Interestingly, however, the proportion of blindness due to optic nerve disorders has decreased from 23.2% in 1999/2000 to 14% in 2009/2010, with a similar decrease noted in partial sight certifications. Considering both blind and partial sight certification, this is mainly due to a reduction in absolute numbers of optic nerve disorders (eg, the number of children certified blind with optic nerve disorder as the main cause was 75 in 1999/2000 and 58 in 2009/2010, and similarly for partial sight, there were 79 certifications in 1999/2000 compared with 61 in 2009/2010). This did not alter if multiple causes were considered and the reason for this decrease is not known. A possible explanation is increasing recognition of cerebral visual impairment as a diagnosis. Such children often have slightly pale or small discs and may have previously been labelled as optic nerve disease when cerebral visual impairment was less recognised.20
The proportion of congenital globe anomalies has also seen a rising trend since the year 1999/2000. This finding reflects a true increase in numbers and, although in keeping with international reports estimating that congenital structural abnormalities are responsible for approximately 15%–20% of blindness and severe visual impairment in children worldwide,1 ,2 ,21 the cause for the increasing trend is not known. However, the largest increase is seen in the subgroup classified as ‘other congenital anomaly,’ which represents a miscellaneous group of potentially poorly characterised ocular, orbital or other neurodevelopmental abnormalities. Albinism and optic nerve disorders each account for approximately 10% of partial sight certifications.
Nystagmus as a single cause for partial sight certification has decreased from 16.7% in 1999/2000 to comprise 10.6% of certification in 2009/2010. This may be due to improved services and availability of diagnostic testing over the study period, particularly for hereditary retinal dystrophy, which may underlie the mirroring trends observed in certification frequency.
In 2003, Rahi and Cable2 reported a high rate of multiple causes of blindness and severe visual impairment in children in the UK and did not report a single ‘main’ cause, reflecting reporting some clinicians’ reluctance to assign a single main cause in this situation, for example, in children with both ROP and cerebral visual impairment. Partly in response to the recognition of the complexity of childhood visual impairment, such that a main cause cannot always be definitively assigned, the CVI form for children was modified to allow reporting of multiple causes. Nonetheless, analysis which includes multiple causes did not reveal major differences in proportions of causes than that using a single main cause.
Our findings suggest that in the UK, similar to other developed nations, cerebral visual impairment is the commonest cause of paediatric SSI certification. Prevention strategies should focus on perinatal care and prevention of premature birth. At present, the scope for intervention against this form of blindness in children is limited. Further research in developing effective methods to quantify visual loss in cerebral visual impairment and interventions to optimise visual stimulation and training is warranted. In terms of service provision, cerebral visual impairment requires a multidisciplinary developmental approach and specialist clinics in order to manage this complex condition.
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Files in this Data Supplement:
- Data supplement 1 - Online figures
Contributors DM wrote the manuscript and analysed the data. CB compiled the database, assisted in analysis and provided senior advice. RW provided senior review. SL and PS assisted with data analysis and assimilation. PC, JR and RB designed the study, assisted in analysis and data presentation and provided senior review.
Funding The research was partially supported by a grant from the RNIB, Guide Dogs and the National Institute for Health Research (NIHR) Biomedical Research Centre based at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology. Data captured by CVI are DH copyright and this work was made possible by collaboration with the Royal College of Ophthalmologists.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.
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