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BJO Online First, published on December 1, 2015 as 10.1136/bjophthalmol-2015-307558 Clinical science
Assessing visual function in children with complex disabilities: the Bradford visual function box Rachel F Pilling,1 Louise Outhwaite,1 Alison Bruce2,3 1
Department of Ophthalmology, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, UK 2 Bradford Institute for Health Research, Bradford, UK 3 Department of Health Sciences, Seebohm Rowntree Building, University of York, York, UK Correspondence to Rachel F Pilling, Department of Ophthalmology, Bradford Teaching Hospitals NHS Foundation Trust, Duckworth Lane, Bradford BD9 6RJ, UK;
[email protected] Received 31 July 2015 Revised 30 September 2015 Accepted 1 November 2015
ABSTRACT Background Assessment of children with complex and severe learning disabilities is challenging and the children may not respond to the monochrome stimuli of traditional tests. The International Association of Scientific Studies on Intellectual Disability recommends that visual function assessment in poorly or noncooperative children should be undertaken in an objective manner. We have developed a functional visual assessment tool to assess vision in children with complex and multiple disabilities. Methods The Bradford visual function box (BVFB) comprises a selection of items (small toys) of different size and colour, which are presented to the child and the response observed. The aim of this study is to establish its intertester validity in children with severe learning disability. The visual function of 22 children with severe learning disability was assessed using the BVFB. The children were assessed by experienced practitioners on two separate occasions. The assessors were unaware of each other’s findings. Results In 15/22 of the children, no difference was found in the results of the two assessors. The test was shown to have a good intertester agreement, weighted κ=0.768. Conclusions The results of this clinical study show that the BVFB is a reliable tool for assessing the visual function in children with severe learning disability in whom other tests fail to elicit a response. The need for a tool which is quick to administer and portable has previously been highlighted. The BVFB offers an option for children for whom other formal tests are unsuccessful in eliciting a response.
BACKGROUND
To cite: Pilling RF, Outhwaite L, Bruce A. Br J Ophthalmol Published Online First: [ please include Day Month Year] doi:10.1136/bjophthalmol2015-307558
Cortical and cerebral visual impairment are the leading causes of registrable visual impairment in childhood in the UK.1 The International Association of Scientific Studies on Intellectual Disability (IASSID) recommends that visual function assessment in poorly or non-cooperative children should be undertaken in an objective manner, and that regular assessment for sensory impairment should occur.2 A study which undertook comprehensive assessment of children in special schools in Scotland found visual impairment (WHO definition) to be present in 12.1%.3 A similar study in Wales found 20% of children with habitual visual impairment.4 However, studies investigating the visual function of children with special needs have been limited in reporting their findings due to the difficulty in achieving a full assessment. This has been reported as being between 10% and 17% of children even by experienced practitioners.3–5 Indeed, in the Scottish study described above,
visual acuity could be reliably assessed in only 190 of 240 children using traditional assessment tools. Assessing vision in this group of children is a challenge due to the often multiple and complex disabilities, which form part of the child’s underlying condition. While in those children with mild learning disability, reasonable adjustments can be made by using picture tests such as Kay pictures6 or preferential looking tests, for example, Cardiff Cards7 or Teller Acuity cards,8 it is the clinical experience of many orthoptists and ophthalmologists that children with moderate to severe learning difficulties lack interest, easily lose attention or fail to provide a robust response to these monochrome stimuli. Even when traditional acuity tests are successful, at low acuity levels, it is difficult for carers and teachers to translate a grating acuity measurement into usable information to assist the child’s learning. Parents like to know how much their child can see, and use this to guide them in selection of suitable toys or stimulation equipment. It has been reported that the use of functional description to enhance the visual function assessment and provide child-specific information to the parents/carers is crucial in ensuring that the child achieves its potential.9 10 In order to improve our success rate in assessing vision in children with complex and multiple disabilities, and allow us to provide realistic childspecific feedback to parents/carers regarding their child’s visual function we have developed a functional visual assessment tool. The Bradford visual function box (BVFB) is used clinically for regular and repeated assessments. It is used in the clinical setting by different assessors, and the aim of this study is to establish its intertester validity in children with severe learning disability.
METHODS Study population Children attending three special schools in Bradford were assessed as part of a programme assessing the visual function of the children in Bradford over a period of 6 months between March 2014 and July 2014. The children attending the schools have severe and complex learning difficulties. Following the Education Act 2014, children with less severe learning difficulties are educated in main stream schools and they are not included in this study. Twenty-two children, age range 4–11 years (median age=10 years) participated. Consent was taken as part of the clinical vision assessment programme in school.
Bradford visual function box The BVFB comprises a selection of items (small toys) of different size and colour, which are
Pilling RF, et al. Br J Ophthalmol 2015;0:1–4. doi:10.1136/bjophthalmol-2015-307558
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Clinical science presented to the child and the response observed. These items were chosen to offer a variety of colours and shapes, to hold the child’s interest. A list of items is shown in table 1. The BVFB is used in conjunction with a checklist for assessing parental or teacher observations of the child’s visual function shown below.
History ▸ Recognise mum/family members; can they find toy; can they tell if it is light/dark? ▸ What sort of toys do they enjoy playing with/what do they enjoy doing? ▸ Variability—does their vision seem OK sometimes and not at others? ▸ Are there concerns about hearing? ▸ Hand movement—can they reach out for a toy? ▸ Head control—can they move their head to follow a toy? ▸ Visual memory—do they look for a dropped toy/dummy? Observations Light perception Bright light in dark room, blink reflex Windmill/flashing ball in dark room Facial perception Do they look at/follow face? Does the child return a silent smile? Fixation Forced choice preferential looking (FCPL) cards, black and white books (1–4) How long can they hold fixation? What is visual attention like? Large toy with/without sound in light Smaller toys without sound (record size/distance)
In this way, comprehensive information regarding the child’s individual visual function is observed and documented. The variable ability and visual attention of this group of children necessitate a flexible approach to test conditions: hence test distance or light conditions are not specified, but were recorded by the tester so a change in function could be identified at a later testing date. Generally, items are presented in room light at a distance of 30–50 cm. The child is given time to ‘find’ the object in their visual field. The object can be slowly moved to a new position and time given for the child to relocate it. If cooperation permits, the child’s visual attention in different parts of the visual field can be assessed by presenting the object silently in four quadrants and the response noted. A positive Table 1 BVFB Target Description
2
Size (mm)
Fixation target
6 10 14 21 28 40 65 70 90 120 130
Red bead Green bead Stripy bead Fish bead Gold bubble Frog Pink spiky ball Pink chicken Fan Baby shape book Push up horse
response may vary from a change in pupil size, a realignment of eyes to locate the object, a movement of head to the object’s new position or an attempt to reach out and grab the object. The response is documented by the assessor. The visual function of these 22 children with severe learning disability was assessed using the BVFB. In all cases, experienced practitioners had been unable to elicit a reliable vision assessment using FCPL tools.8 The children were assessed by practitioners experienced in paediatric vision assessment; a specialist orthoptist and a paediatric ophthalmologist, on two separate occasions. The assessors were unaware of each other’s findings. The targets were presented in a random order and at a distance of between 30 and 50 cm, depending on the child’s responses the fixation targets were decreased in size until the practitioner was unable to yield a response from the child. Because of the difficulties in establishing a definitive end point, the practitioners graded the child’s responses on a 4-point scale; 0—no response/very uncertain of result, 1—variable response—uncertain of result, 2—reasonable response—somewhat certain of result and 3—excellent response—very certain of result. This was used as a comparison to the results of the visual function measure.
Strabismus Cover test and/or observational assessment were carried out by the orthoptist at the time of the visual function assessment.
Refractive error After the visual function assessment a non-cycloplegic refraction was carried out on 22/22 of the children by an experienced paediatric ophthalmologist. A mean spherical equivalent (MSE) (sphere plus ½ cylinder) was calculated for each eye. Hypermetropia was defined as a MSE of +2.00 Dioptres sphere (DS) or more. Myopia was defined as a MSE of ≤−0.50 DS and astigmatism as ≥0.75 Dioptres cylinder (DC).
Statistical analysis Descriptive statistics are used to present the number and percentage of children with strabismus and refractive error. A weighted κ was used to compare the agreement between the results of the two assessors. All statistical analyses were carried out using Stata V.13.1 (StataCorp, Texas, USA).
RESULTS All 22 (100%) children were assessed and produced a positive response to the visual assessment using the BVFB. No child had to be excluded. Seven (32%) children were found to have either a constant or an intermittent manifest deviation. Three children had an intermittent exotropia, two constant exotropia and two constant esotropia. Sixteen (73%) children were found to have a refractive error (table 1). The MSE was 0.82 dioptres (range −4.25 to +4.50). In 15 (68%) children no difference was found in the results of the two assessors. As would be expected, in those children for whom reliability score was good (2 or 3), there was little or no difference between assessors. In four children assessor 1 graded better by one target size, in two children assessor 2 graded better by one target size, and in one child assessor 2 graded better by three target sizes (table 2). This child (subject 3) was graded with a poor reliability score (1) by both assessors. The test was shown to have a good intertester agreement, weighted κ=0.768. Pilling RF, et al. Br J Ophthalmol 2015;0:1–4. doi:10.1136/bjophthalmol-2015-307558
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Clinical science Table 2 Results Subject
Age (years)
Assessor 1 (target size, mm)
Assessor 2 (target size, mm)
Difference (target size)
Reliability assessor 1
Reliability assessor 2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
10 9 10 12 10 10 8 9 7 4 8 6 6 6 10 10 11 12 11 11 12 11
6 65 21 6 6 21 6 6 6 * 21 6 6 6 6 10 6 6 65 6 6 40
6 40 6 6 6 21 6 6 6 120 21 6 6 6 6 10 6 10 65 10 10 65
0 1 3 0 0 0 0 0 0 n/a 0 0 0 0 0 0 0 1 0 1 1 1
2 1 1 2 2 2 3 3 3 0 3 2 2 2 3 3 3 1 1 3 3 1
2 1 1 3 2 2 3 3 3 1 3 2 2 2 3 3 3 2 1 3 3 1
*Assessor 1 did not think the child was able to see the largest toy size.
DISCUSSION The results of this clinical study show that the BVFB is a reliable tool for assessing visual function in children with severe learning disability in whom other tests fail to elicit a response. It demonstrates that it is feasible to demonstrate a repeatable form of visual function measure in this population. The premise of a test which does not require a verbal or gross motor response from the child is not a new one.11 While some children may reach out or turn to track the object, those with gross development delay may respond with pupil constriction or a change in behaviour (for instance temporarily halting self-stimulation such as rocking or humming) in response to a visual stimulus. Our study reports that 13 (60%) of the children required a refractive prescription, this is greater than that of Das et al who found 46% of their study population to require glasses.3 Seven (32%) children had a strabismus, this is greater than that of the study reported by Neilsen et al assessing visual dysfunction in children with developmental delay.12 Both studies were carried out prior to the Children and Families Act 2014, which supports the inclusive education of children with special educational needs in mainstream school. The profile of the population of children in our study educated in special schools; the majority of children having severe disability and complex needs may explain the differing results. The visual information gained from the assessment using BVFB allows parents and carers to instantly “see what their child sees” and practitioners are able to explain to carers that the child is visually alert to objects of a certain size, in a certain area of their field of vision. While not a formal visual field assessment, the BVFB can be used to demonstrate if the child has visual inattention in a particular area of their visual field— indicated by a slower or absent response on one side or another. This information can then be used by the carer, for example, when feeding the child. Special schools commonly use picture exchange communication system or Tobii devices—using cards Pilling RF, et al. Br J Ophthalmol 2015;0:1–4. doi:10.1136/bjophthalmol-2015-307558
or pictograms to communicate with children and offer choice. The BVFB can help inform educators of an appropriate size of picture card, or the area of visual field in which to present the image to the child to facilitate effective use of these systems. This type of practical information has been shown to be important to carers in everyday living.9 Since the introduction of the BVFB to clinical use in Bradford, parents and carers have commented on the improvement in feedback they receive regarding their child’s vision. In some cases, children previously thought not to be able to see have responded to the BVFB and the carers have used the information gained to develop strategies for their child to maximise their visual function. The intertester validity of the BVFB is good; however, we recognise that there are limitations. The BVFB is limited in its scientific robustness by the variability in colour of the objects, lack of contrast sensitivity measurement, variability in the test distances and background that different practitioners may use. The need for a tool which is quick to administer and is portable has previously been recognised11 and is supported by the Health and Social Care Act (2012), which requires services to reduce inequalities between patients in respect of ability to access services and outcomes achieved. While the BVFB is not a replacement for widely accepted tests such as Cardiff cards7 or Force Choice Preferential Looking,8 the BVFB offers another option for children for whom these tests are unsuccessful in eliciting a response. The usefulness of the BVFB in providing a quantifiable, repeatable objective measurement of the child’s vision for both the practitioner and the parent/carer cannot be overlooked. Acknowledgements The authors are grateful to the carers, the teaching staff and the orthoptists who participated in and organised the vision assessments. Contributors RP designed the BVFB, monitored data collection, drafted and revised the paper. LO collected and monitored data collection, AB initiated the project, designed data collection, wrote the statistical analysis plan, analysed the data and revised the draft paper. 3
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Clinical science Funding AB is funded by a National Institute for Health Research Post-Doctoral Fellowship Award (PDF-2013-06-050). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The Bradford visual function box used in the study was funded by a grant from the British and Irish Orthoptic Society. Competing Interests None declared.
5
6 7
Provenance and peer review Not commissioned; externally peer reviewed. 8
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Pilling RF, et al. Br J Ophthalmol 2015;0:1–4. doi:10.1136/bjophthalmol-2015-307558
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Assessing visual function in children with complex disabilities: the Bradford visual function box Rachel F Pilling, Louise Outhwaite and Alison Bruce Br J Ophthalmol published online December 1, 2015
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