Eye (2002) 16, 557–561 2002 Nature Publishing Group All rights reserved 0950-222X/02 $25.00 www.nature.com/eye J Alagaratnam, TK Sharma, CS Lim and CLINICAL STUDY A survey of visual BW Fleck impairment in children attending the Royal Blind School, Edinburgh using the WHO childhood visual impairment database Abstract Introduction Purpose To assess the aetiology and The prevalence and major causes of childhood changing patterns of childhood blindness in blindness vary between countries and over one school for the blind in the UK and to time. The WHO Prevention of Blindness assess the use of the World Health Program with the International Centre for Eye Organisation Prevention of Blindness Health has developed a standard methodology (WHO/PBL) methodology and reporting form and reporting form to record the causes of in a developed country. visual impairment in children.1 The Methods One hundred and seven children methodology has been used in developing in one school for the blind and visually and middle income countries.1–3 impaired in Edinburgh were examined using This study was undertaken in order to the WHO/PBL childhood blindness assess this method in one school for blind assessment form. children in the UK. There have been two Results Of the 107 children examined, 87 previous surveys of visual impairment in The (81%) were blind or severely visually Royal Blind School, Edinburgh.4,5 These impaired (corrected visual acuity of Ͻ6/60 studies and studies from other developed (20/200) in the better eye). Perinatal related countries6 were presented in a non- blindness (40%), hereditary disease (26%) standardised way, which makes it difficult to Department of and developmental factors (26%) formed the monitor changing patterns of childhood Ophthalmology three largest aetiological categories. blindness over time. Royal Infirmary Conclusion The pattern of childhood The aims of this study were to apply the Edinburgh, UK blindness seen in this study was similar to WHO/PBL reporting form in a UK school for Place of Study: reports from other developed countries. The the blind and to compare the findings with Royal Blind School WHO/PBL reporting form allows detailed data from schools in developing countries. Craigmillar Park comparisons between countries and over Edinburgh, UK time. Additional fields for more detailed reporting of cerebral visual impairment and Patients and methods Correspondence: BW Fleck associated handicaps would increase the Department of usefulness of the WHO/PBL form for The Royal Blind School, Edinburgh serves Scotland and the North East of England. The Ophthalmology population-based studies and for use in Princess Alexandra Eye developed countries. school caters for both residential and day Pavilion students. Many blind children are now Eye (2002) 16, 557–561. doi:10.1038/ Chalmers Street Edinburgh EH3 9HA, UK sj.eye.6700149 educated in their local school with additional educational support and the role of special Tel: 0131 536 3905 schools for blind children has changed in the Fax: 0131 536 3735 E-mail: Brian.FleckȰ Keywords: childhood blindness; congenital UK. Since 1990, the Royal Blind School luht.scot.nhs.uk cataract; hereditary blindness; Edinburgh has been divided into two sites microphthalmos; retinal dystrophies; with nursery, primary and secondary Financial or proprietary retinopathy of prematurity education at the main school site and a interest: none A survey of visual impairment using WHO/PBL methodology J Alagaratnam et al 558 residential, multiple handicap unit (MHU) at a second 20 had no functional vision. This latter group showed site. response to light or even movements of large objects During the academic year 1999–2000, all 107 children during testing but showed no evidence of visual at the school were examined by one consultant behaviour during daily activities. A total of 57 children ophthalmologist (BWF). Information was gathered therefore had residual vision and the remaining 50 had using interviews with pupils, parents and school staff no functionally useful vision. Two children had visual and by consulting hospital and community health acuity of 6/18 or better. These children had profound records for each child. perceptual visual dysfunction. Binocular visual acuity, and when possible, uniocular visual acuity were measured using a range of Anatomical cause of visual loss techniques. These included Keeler grating cards, Cardiff cards, Kay pictures, Sheridan–Gardinar test The anatomical sites of abnormality leading to visual cards, and Snellen charts. Visual fields were assessed impairment or blindness are given in Table 2. Disease by confrontation, and by the history given by carers. or malformation of the central nervous system or optic Refraction with cycloplegia was carried out. Anterior nerve was the commonest cause of visual impairment segment examination was performed using a slit-lamp and was present in 53 (50%) children. Combined optic or flashlight. Posterior segment examination was atrophy and cerebral visual impairment were seen in performed by indirect ophthalmoscopy after mydriasis. 28 children. Seven children had cerebral visual All data were recorded on the WHO/PBL eye impairment without optic atrophy. Optic atrophy was examination record for children with blindness and responsible for visual impairment in nine children and low vision. The form is accompanied by instructions bilateral optic nerve hypoplasia in nine children. for use, definitions and methods of classification. For Retinal disease was the second most common cause each child, the cause of visual loss was recorded using of visual impairment, present in 39 (36%) children. the anatomical and aetiological classification used in Nineteen children had bilateral retinal detachment due the form. to retinopathy of prematurity. Retinal dystrophies were present in 13 children, of whom seven were diagnosed as Leber’s amaurosis. Two children had been treated Results for bilateral retinoblastoma. One hundred and seven children were seen. Sixty-six Congenital anomalies of the whole globe, such as were attending the main school campus and 41 the anophthalmos and microphthalmos, were present in 12 MHU. There were 54 males and 53 females. Two (11%) children. Corneal opacity was relatively children were of Middle Eastern origin, one was uncommon. One child had sclerocornea. There were Chinese, one was from Pakistan and all the remaining two children with visual loss due to congenital children were Caucasian. Seventy-five (70%) of the glaucoma. There were no cases of visual impairment children were aged 11 years or over, 31 (29%) were due to congenital cataract. aged 5–10 years, and one (1%) was less than 5 years. The distribution of visual acuities is given in Table 1. Aetiological category of visual loss Within the group of 42 blind children with visual acuity Ͻ3/60 but with at least perception of light The causes of visual impairment are classified vision, 22 had detectable residual visual behaviour and according to the time of known insult in Table 3. Ninety-one (85%) had visual impairment by the age of Table 1 WHO categories of visual impairment. Distribution of binocular visual acuity Table 2 Anatomical classification of the causes of visual impairment WHO category Visual acuity Total Total number percentage Anatomical site n % Blind NPL 30 28% Optic nerve/CNS 53 50% Blind Ͻ3/60-PL 42 39% Retina 39 36% Severe visual Ͻ6/60 to 3/60 15 14% Whole globe 12 11% impairment Glaucoma 2 2% Visual impairment Ͻ6/18 to 6/60 18 17% Cornea 1 1% No impairment 6/18 or better 2 2% Lens –– Uvea –– Total 107 100% Total 107 100% NPL = No perception of light. PL = Perception of light. Eye A survey of visual impairment using WHO/PBL methodology J Alagaratnam et al 559 Table 3 Causes of visual impairment by timing of aetio- the elimination of avoidable blindness by year 2020.7 It logical insult has been estimated that there are 1.5 million severely Timing of aetiological insult n % visually impaired and blind children worldwide. The recorded prevalence of SVI/BL in European countries Perinatal 43 40% varies from 0.1 to 0.41 per 1000 children.6,8 There are a Hereditary 28 26% 2,3 Intrauterine 3 3% number of blind school studies from South Asia, 9 10,11 Childhood 5 5% South America and Africa. The causes of blindness Others (‘Developmental’) 28 26% vary from country to country and over time. There are Total 107 100% few data available concerning the causes of childhood blindness in Scotland and a variety of definitions and classifications have been used in previous studies.4,5 1 year and, of these, at least 48 (45%) had visual This blind school study using the WHO/PBL eye impairment at birth. examination form is the first reported in the United Perinatal factors were identified in 43 (40%) children, Kingdom. with prematurity the largest single group. Visual This is a small study in a selected population and impairment was attributed to genetic diseases in 28 the results should be interpreted with caution. (26%) children, most commonly optic atrophy or Integrated education of visually impaired children is retinal dystrophy. Parental consanguinity was present now preferred when possible. A range of uncontrolled in only one family. Intrauterine factors such as factors such as an increased prevalence of multiple congenitally acquired rubella and congenital handicaps and increased severity of visual impairment toxoplasmosis was present in only three (3%) children. may have led to population bias in this study. The In the childhood onset group trauma or tumour had study results are therefore likely to differ from whole occurred in five (5%) children. Developmental factors population studies. contributed to visual impairment in 28 (26%) children. The commonest anatomical site of disease was the In many of these genetic abnormalities undetectable by brain and optic nerve. While it can be difficult to current techniques may have been present. differentiate brain and optic nerve disease, some attempt to do this is helpful.