Paediatric low-vision assessment and management in a specialist clinic
in the UK
JULIE LENNON, ROBERT HARPER, SUS BISWAS AND CHRIS LLOYD
Manchester Royal Eye Hospital, UK
ABSTRACT
This article presents a survey of the demographical, educational and visual
functional characteristics of children attending a specialist paediatric lowvision assessment clinic at Manchester Royal Eye Hospital. Comprehensive
data were collected retrospectively from children attending the paediatric lowvision clinic between January 2003 and August 2004 (n = 64). Data collected
included clinical and demographic details and educational status. Use was
made of a pre-clinic questionnaire to ascertain information regarding
schooling and level of support, and child, parental or specialist teacher
concerns. Visual functions assessed included distance IogMAR acuity, near
acuity, contrast sensitivity, colour vision and when feasible, visual fields.
Following refraction, children were evaluated for spectacles and low-vision
aids. A key finding to emerge from this study is that children attending the
clinic present with a range of visual disorders and levels of visual function.
The most common cause of visual impairment was albinism (20%) followed
by rod cone dystrophy (10%). It is concluded that a comprehensive
assessment of visual function should, when reported to other professionals,
permit more relevant adaptations to be incorporated into the educational
strategies adopted for the child.
KEY WORDS
children, low vision, low-vision aids, paediatric, visual
impairment
INTRODUCTION
There has been little data published on the visual function characteristics of a
paediatric low-vision population in the United Kingdom. Visual loss in
childhood has been shown to have widespread implications in the social and
educational development of a child (Kelley et al., 2000; Sacks and Silberman,
2000). Due to the underlying developmental, educational
and long term social and economic issues facing children with visual
impairment (VI), it is important that these children are identified early in life to
ensure that they receive the relevant interventions at appropriate times in
their lives (Cass et al., 1994; Gould and Sonksen, 1991). Kelley et al. (2000)
estimated that 80 per cent of school tasks are based on vision, highlighting
the essential role of a comprehensive visual assessment in all children with
VI, both prior to commencing formal education, and as they progress through
the school years.
Local Authority Social Services departments are responsible for compiling
data on blind and partial sight registration in England. In March 2003, there
were 8770 children between the ages of 0-17 years on this register, with 110
children on the blind register, and 125 on the partially sighted register
resident in the Manchester Metropolitan District (Department of Health, 2003).
However, this register is considered to grossly underestimate the number of
school age children with VI, with estimates of the actual number being nearer
24,000 (Keil, 2003).
Current low-vision clinical service provision is predominantly Hospital Eye
Service based, with 65 per cent of the total annual low-vision appointment
capacity being made available via this provider (Culham et al., 2002).
Additional low-vision services are also provided by Local Educational
Authorities and voluntary organizations. It is evident, however, that the needs
of a paediatric low-vision population will differ greatly from an adult population
(teat, 2002), and models of paediatric low-vision care can comprise a number
of key professionals involved in the child's social, educational and
developmental welfare. Information on the child's current status may be
collected from a variety of sources, thus providing the low-vision clinician with
important information on, for example, the child's habitual visual environment,
their restrictions in activities and the presence of learning disabilities.
Assessments can be made open to parents, teachers and other support
workers to ensure a more integrated service is provided. Information, advice
and appropriate low-vision aids (LVAs) can be offered as deemed necessary
for the child, and review and feedback methods can be tailored to meet individual requirements. A report commissioned by the Welsh Assembly
Government (2004), stated that where there were established working
relationships between health and social service providers, referrals to the
relevant support services were more frequent and more appropriate. The lowvision clinician can play an important role in this multidisciplinary team, by
providing a comprehensive visual assessment and by making appropriate
recommendations in respect of the child's visual environment.
In the past, all school age children referred to the Manchester Royal Eye
Hospital low-vision clinic were assessed in a general low-vision clinic. In
October 2002, a specialist paediatric low-vision clinic (PLVC) was established
in order to provide a more comprehensive evaluation for all new referrals of
school age children. The purpose of this paper is to present survey findings of
the clinical, demographic and educational status of children assessed in this
clinic, and to provide a detailed description of their visual function and LVA
provision.
METHODS
Manchester Royal Eye Hospital provides a regional paediatric ophthalmology
service within the north-west. Referrals to the PLVC are, therefore, not
restricted to children in the Manchester Metropolitan District, provided the
child is a hospital patient. The aim is to offer a low-vision assessment for all
new patients within four weeks of receipt of referral. A pre-clinic questionnaire
is sent with the appointment letter to parents to collect preliminary data
regarding the child's educational status, level of support and concerns, and
also to establish preliminary goals for the assessment. The appointment letter
also contains an open invitation to other professionals involved in the child's
educational welfare, at the parent's request. A full history and symptoms is
then undertaken at the initial clinic visit.
The PLVC is delivered in a child friendly environment, with tests tailored
towards the child's individual abilities. Refraction (with cycloplegia if
necessary) is carried out if the child has not been refracted in the last six
months, or if change is suspected. Best corrected distance IogMAR acuity is
assessed using either the EDTRS or Lea symbol charts. Near visual acuity is
measured with the Maclure or MassVAT charts. Low contrast letter
sensitivity/contrast sensitivity is recorded monocularly and binocularly with the
Pelli-Robson low contrast letter chart or Hiding Heidi charts. Where cooperation permits, colour vision is assessed with the PV16 test (large panel
D15). Accommodation is also measured when indicated from history,
symptoms or from the diagnosis, using either a dynamic retinoscopy
technique or a subjective push-up test. Finally, visual fields are evaluated
using an informal confrontation test, or more formally with the Goldmann bowl
perimeter or Humphrey visual field analyser. Appropriate LVAs are
demonstrated and suitable devices loaned to the child following handling
instruction and brief training.
Following the low-vision assessment and obtaining informed consent, a
detailed report is sent to relevant professionals involved in the child's
education and healthcare, and copied to the child's parents or care The report
summarizes the findings of the assessment in non-technical language,
providing information on diagnosis and prognosis, t impact of the VI on tasks
and activities, and advice on the use of spectacles, LVAs, lighting, working
distance, and other adaptations with the environment that might be of benefit.
Prospective data were collected for all children who attended f their first lowvision assessment at the PLVC during the period January 2003 to August
2004. All assessments were carried out by one of t optometrists (JL and RH),
working to an assessment guideline. comprehensive dataset was collated for
all children assessed, including the following: referral source, age, sex,
primary diagnosis, registration status, educational status, details of current
support in school/ statementing, use of adaptive devices and non-optical
LVAs, current optical LVAs, use of spectacles and the detailed visual
functions described above.
RESULTS
Clinical and data, and educational status
Over the twenty-month period, 64 children attended the PLVC. A
comprehensive data set was available in each case. Figure 1 shows the
source of the initial request for a low-vision assessment, with the majority
(62%) being internal referrals from ophthalmologists. A total of 34 of the 64
(53%) children who attended the PLVC were male and 30 (47%) were
female. Table 1 shows the range of eye conditions (i.e. primary diagnosis)
amongst this group of children. The most common diagnosis was albinism
(20%), followed by rod-cone dystrophy (10%) and aniridia and optic nerve
hypoplasia (8%). Many children had secondary ocular abnormalities,
including nystagmus, which was present in 51 of the 64 children (80%) but
was considered to be the primary cause of VI in only one child.
All school ages were represented in the sample, with the youngest aged 4
and the eldest aged 16 (Figure 2). A total of 38 children were registered as
partially sighted, 13 as blind and 11 were not registered. The registration
status of two children was unknown. Only 6 of the children attended special
schools for VI, or received a significant proportion of their education in a
specialized VI unit. The remaining 58 children attended a mainstream school
and took the majority of lessons alongside their peers. Seven children who
attended the clinic were identified as having learning disabilities.
Initial source of referral
Figure 1. Initial source of referral into the paediatric low-vision clinic
(n = 64)
Table 1
Primary diagnosis (n = 64)
Retinal dystrophy
23 (2*)
Developmental anomaly of the globe
31
Optic neuropathy
3 (1 *)
Anterior segment anomalies
4
ROP
2
Nystagmus (as primary cause)
1
*number in brackets indicates associated syndrome
Age at initial assessment
Figure 2. Age of child at initial assessment (n = 64)
Thirty-eight (59%) of children had a statement of Special Educational Needs
(SEN). Twenty had not undergone the statementing process, and in the case
of two individuals, information regarding statementing was unknown.
Although 59 per cent of children had a statement of SEN, additional
classroom support was received on at least a weekly basis by 84 per cent of
children.
When questioned on the use of adaptive devices, 61 per cent of the pupils
reported having made previous use of at least one non-optical aid. These
aids ranged from simple reading and writing stands to adapted computers
and local task lighting. Enlarged print was the most common method of
improving access to printed material, with 49 children (76%) having print
enlarged in school. Although class work was usually enlarged, homework did
not appear to be enlarged with the same frequency, leading to reported
difficulty completing homework tasks.
The N notation of print used in school was established either from the preclinic questionnaire, from actual school material brought to the assessment,
or by estimation in the clinic. Figure 3 shows the estimated font sizes used in
school, with this figure ranging from N14 - N100, with N18 being the most
commonly used font size. Font enlargement was usually achieved by
photocopying or using a scanner. Two of the children in our sample were
learning braille, one of whom also made use of printed material in some
circumstances.
Estimated font size used in school
Figure 3. Estimated font size used (n = 49)
Visual functions
On presentation to the clinic, 41 (64%) children already wore a spectacle
correction. Subsequent to refraction, a total of 37 prescriptions were issued.
Twenty-one of these prescriptions were an update for existing spectacle
wearers, either due to a change in prescription or through general spectacle
wear and tear. The remaining 16 were prescribed to first time wearers, either
to correct a previously uncorrected refractive error, or to deal with discomfort
glare or photophobia.
Of the 37 prescriptions issued, a total of 43 pairs of spectacles were dispensed, since some children required two pairs, either because a dark tint
was prescribed for outdoor use with a lighter tint or a clear pair being required
for indoors, or, as in one case, a pair of bifocals were prescribed for general
use and single vision pair for sport. The majority (n = 37, 86%) of spectacles
prescribed were single vision, with 26 (60%) having some form of tint
incorporated. Six prescriptions (14%) had a near-vision component.
Visual acuity was measured following refraction and the results are depicted
in Figure 4. The mean threshold visual acuity was 0.81 ± 0.31 IogMAR for
distance (i.e. 6/38 ± 3 lines on the IogMAR chart) with a range of 0.2 to 1.76
IogMAR. The mean threshold best corrected near visual acuity was N9.2 ± 6
with a range of N5 to N36, and a modal value of N5 (this value being
achieved by 25 children). The working distance used to achieve the optimum
near visual acuity ranged from the print being held at 'nose' to 26 cm (mean =
12.6 ± 5.6 cm).
Optimum distance visual acuity
Best corrected distance visual acuity following refraction
Figure 4. (n = 62)
Contrast sensitivity or low contrast letter sensitivity was measured in 62 of the
64 children. Four children were assessed using the Heiding Heidi cards and
achieved a contrast sensitivity of 2.5, 10, 25 and 100 per cent respectively.
The remaining 58 children were measured on the Pelli Robson chart and their
results are shown in Figure 5, with the mean low contrast letter sensitivity
being 1.47 ± 0.38logCS (approximately 2.8%), with a range of 0.30 to 2.10
IogCS (i.e. 44% to 0.7%).
An assessment of colour vision was made in 56 children (87%) using the
PV16 test. A total of 29 children made no errors, suggesting they did not have
a gross colour vision defect. Twenty-five children (44%) made errors,
although this figure includes those who made a single transposition error
(considered a 'pass', with more than one minor error, or an error line across
the colour circle being considered a 'fail' (Birch, 2001)). The results for two
children were indeterminate.
Low-vision aids
The need for a telescopic aid was identified in 39 of the 64 children. Of these
39 children, five already had a distance aid that had been provided through
alternative sources (including specialist teachers, local optometrists or self
purchase). Following the assessment, one child received an alternative
device, as a change in the level of magnification was needed, and four
children's current aids were deemed suitable. The remaining 34 children were
loaned their first distance LVA, with 17 receiving a monocular and 17
receiving a pair of binoculars. The distance aids prescribed were either four
times, six time or eight times devices.
Contrast sensitivity
Figure 5. Best corrected contrast sensitivity (n = 58)
The best corrected visual acuity with the prescribed distance aid was
measured in the clinic after a period of instruction. Figure 6 shows a
comparison of the visual acuities with and without the prescribed distance
visual aid for the 35 children who were loaned a new device in the clinic. The
average number of lines of improvement in acuity with the distance vision aid
was 0.67 ± 0.27 IogMAR (i.e. almost seven lines on the IogMAR chart)
(p < 0.01).
A near-vision assessment for optical LVAs was also carried out on all 64
children. Again, as with the distance aids, some of the children already
possessed a near-vision aid, which had been prescribed elsewhere. Prior to
the PLVC assessment, 29 near LVAs were already owned, with a further 41
near LVAs dispensed following assessment. The most commonly prescribed
aid was a 1.8x brightfield magnifier, given to 61 per cent of children. The least
commonly prescribed near aid was the hand held magnifier, of which only two
were prescribed (a 3x and a 3.5x). Of the 14 stand magnifiers prescribed, the
majority (71 %) were 6x, with the remainder being either 8x or 10x. In total, 70
near LVAs were given to 52 children, giving a range in acuities from N5 to
N24 and a modal value of N5 (achieved by 36 children). A comparison of
near visual acuities obtained with and without the near LVAs is shown in
Figure 7.
Figure 6. Comparison of distance VA with and without prescribed
distance LVA (n = 35)
Optimum VA measured with LVA (IogMAR)
Figure 7. Comparison of near VA with and without prescribed near
LVA (n = 62)
Twenty children given a near-vision aid could already access N5 font prior to
using the aid but the aid allowed them to use an increased working distance
to read N5 font.
DISCUSSION
Clinical and demographical data, and educational status
The primary causes of VI in this group of children were found to b diverse. In
our sample, congenital genetic conditions such as albinism and rod cone
dystrophy were the most common. This is in line with the findings of LovieKitchin and Bevan (1982) and Leat and Karadshe (1991) who found
congenital and hereditary conditions to be the pr dominant cause of VI in
children. Interestingly, congenital cataract w the most common primary
diagnosis in these studies, but accounts only one case in this survey.
However, the incidence of VI due to co genital cataract has been shown to be
on the decline from 1969 to 19 (Rahi and Dezateux, 1998). Only one case of
cortical visual impairment (CVI) was documented, a finding that is in contrast
to some studies which have found CVI to be the principal cause of serious
visual to among children in developed countries (Rogers, 1996 and Du et al
2005). Possible reasons for this discrepancy might include the source
referrals and the limited awareness of the PLVC. In relation to the former
reason, children with CVI are less prevalent in ophthalmology clinics (Hou et
al., 1999), the major referral source for our clinic.
An interesting finding in the present study was that only seven children (11 %)
were identified as having learning disabilities. This number is considerably
less than has been found in the previous studies (Flanagan et al., 2003;
Kirchner, 1990), where around half of all children with VI had additional, nonophthalmic impairments. Rogers (1996) found only 35 per cent of their
sample had VI alone, and of the remaining 65 per cent of the children, 49 per
cent had CVI and 89 per cent had learning difficulties. The reason for this
discrepancy is probably because children with learning difficulties are less
likely to be referred for low-vision assessment.
Arguably these children may not have had their VI identified due to the
complexity of other motor and communication difficulties (Dutton, 2003).
Similarly, those children with CVI frequently have multiple disabilities,
including learning disabilities. Arguably, this contrast in findings reflects a
possible gap in service provision to children with CVI and/or those with
learning disabilities.
Our survey suggests that 80 per cent of children in the clinic had their visual
impairment registered, despite the fact that all of the children assessed would
be classified as having low vision according to the World Health Organization
(1992). However, this classification is not synonymous with the
BD8/Certificate of Visual Impairment registration criteria, a register that has
previously been shown to under-represent true prevalence figures, at least in
adults (Bruce et al., 1991).
The age range of children in our sample was 4-16 years. Only seven children
were seen at the reception/year 1 stage of primary school. Ideally, a child with
visual impairment should be referred for an initial LVA assessment in the preschool years (teat, 2002). It has been argued that children should have
access to support services before reaching school age, as the general
development of the child can be greatly influenced in the pre-school years of
life (Gould and Sonksen, 1991). A developmental level of two years of age
has been shown to be adequate for using a stand magnifier (Ritchie et al.,
1989). Ways of promoting the service to a younger age group, especially for
those just entering school should be explored, possibly through orthoptists
and/or school nurses involved in vision screening at school entry.
In our sample, 91 per cent of children received the majority of their education
in a mainstream setting. The educational system for children with visual
impairment changed radically following the Warnock report (Warnock, 1978)
and ensuing Education Acts (1981 and 1996). Man 'Special Schools' were
subsequently closed and the current emphasis now on inclusion of children
with VI into mainstream settings.
Access to specialist equipment and appropriate adaptations to teaching
materials, has allowed children with all degrees of VI to be educated along
side their peers. The low-vision clinic should thus be recognized playing an
important role in a child's integration.
Statements of Special Educational Needs (SEN) were introduced following
the 1981 Education Act. The consequent 1996 Education Act, in conjunction
with the Code of Practice, offers arrangements for the identification and
assessment of SEN. Not all children with VI have undergone statementing,
indeed only 59 per cent of the children in sample either had a statement of
SEN or were undergoing the statementing process as a result of their VI. This
proportion is greater than figure of 46 per cent previously reported by Blaikie
et al. (2003), since it is self-evident that children registered with ophthalmic
consult will have their VI communicated to the education authorities, e.g.
through the certification process.
In the present survey, additional support was usually provided by a qualified
teacher for the visually impaired or a learning assistant. As might expected,
the level of support varied from child to child. Although only 59 per cent had a
statement of SEN, additional classroom support w received on at least a
weekly basis by 84 per cent of children, showing that a statement of SEN is
not always necessary to ensure that a child receives assistance. This
suggestion is supported by other findings (Keil, 2003 where 96 per cent of
Educational Authorities Local VI services support all children with VI
regardless of whether or not they had a statement SEN, although interestingly
not all those who had a statement of SEN our sample reported receiving
regular classroom assistance.
Visual function assessment
On presentation to our clinic, 64 per cent of children were already spectacle
wearers. Following refraction, 70 per cent of the previously no spectacle
wearers were found to require a refractive correction. In total 57 of the 64
children (89%) were deemed likely to benefit from spectacle wear, although in
some cases the child benefited more from incorporation of a tint rather than
the refractive correction. The findings of the present survey agree with others
(Du et al., 2005; Nathan et al., 1985 that a significantly high proportion of the
paediatric low-vision population have, and are likely to benefit from, refractive
error correction.
In our sample, six children (9%) were prescribed spectacles with a near
addition; this is less than the 14.6 per cent prescribed by Leat and Karadsheh
(1991) and 34.9 per cent prescribed by Lovie-Kitchin and Bevan (1982). Near
prescriptions were issued when a reduced level of amplitude of
accommodation was found and visual acuity improved with the reading aid.
Assessment of accommodation function is vital in children with visual
impairment, mainly to ensure their accommodation function is adequate to
maintain the close working distances employed when carrying out near-vision
tasks. Certain conditions have been shown to be associated with reduced
accommodation, including Down's syndrome and cerebral palsy (teat, 1996;
McClelland et al., 2006; Woodhouse et al., 2000), and fluctuating
accommodation has been demonstrated in children with albinism and
idiopathic nystagmus (teat et al., 1999). Our sample contained only a small
number of children diagnosed with conditions associated with known
accommodation inaccuracies which may account for the lower than expected
number of near-vision spectacles prescribed.
As might be expected, the mean contrast sensitivity was reduced from normal
levels in many children. Arguably, contrast sensitivity provides information on
visual performance that more closely matches 'real world' vision.
When reduced contrast sensitivity is found, advice can be given on contrast
enhancing methods and in the report a fuller description of contrast visual
performance can be offered. Somewhat surprisingly, a number of children
displayed contrast sensitivities near 'normal' values of 1.69 IogCS (Myers et
al., 1999), in particular those children with albinism.
A significant percentage of our sample (44%) showed the presence of
possible colour confusions. This is greater than the eight per cent of males
and 0.5 per cent of females in the general population with a congenital colour
vision defect (Birch, 2001). Indeed, the prevalence of colour vision defects in
the low-vision population has been shown to lie between 24 and 66 per cent
(Kalloniatis and Johnston, 1990; Refson et al., 1999). This can have
implications in certain educational materials and career choices and is
highlighted in the report to parents accordingly.
The high prevalence of nystagmus in the sample (80%) also highlights the
importance of documenting this abnormality, including the possible presence
of any nystagmus 'null point', a finding that can be useful information to
convey to those involved in the child's care and education (e.g. classroom
seating position).
Low-vision aids
In those prescribed a distance LVA, a mean improvement in visual acuity of
0.67 ± 0.27 IogMAR was found with the distance aid. Sever the children did
not achieve the predicted level of visual acuity their distance aid, and indeed
one child actually demonstrated a in acuity using a distance vision aid. This
discrepancy between predicted and achieved acuity may be because the
optical aid was new to many of the children, some of whom struggled with
focusing the device. Other reasons for lower than anticipated acuities include
restricted visual fields and reduced contrast sensitivities.
However, it would be expected that with suitable training, the child should
achieve a level of visual acuity closer to the predicted value (Jose, 1983).
In respect of near vision, while only 39 per cent (n = 25) of children achieved
a near visual acuity of N5 without an LVA, 69 per cent (n =' achieved N5 with
an LVA in the clinic. Twenty of these 36 children c already access N5 font
prior to using the aid, but the aid allowed the use an increased working
distance to read N5 font. The remaining children could only access N5 print
with the use of a magnifier. The commonly prescribed near aids were low
power one point eight times brightfield magnifiers (61%). Relatively few handheld devices issued (only 5%), possibly due to the increased difficulty in
maintaining focus with hand held devices for prolonged periods of time.
Near-vision aids were issued to promote independent access to small print
and a prolonged reading with a more comfortable posture.
CONCLUSION
In summary, this initial survey shows that children are present w wide range
of visual disorders and levels of visual function. An assortment of low-vision
aids and management strategies must be covered when assessing the
paediatric population. The comprehensive assessment of VI, combined with a
more multi-disciplinary approach and child-centred environment for
assessment, should contribute to an enhanced level of care. Preliminary
feedback from parents, teachers and children is positive, although a more
systematic evaluation of PLVC service outcomes would be worthwhile. It is
hoped improved communication can enhance the prospects of a more
integrated service for children with VI, where the LVA provision can be
incorporated into the educational strategies adopted for the individual. While
this study does not specifically provide data in respect of benefits of interprofessional collaboration, an established working relationship between all
professionals is arguably crucial to providing a comprehensive efficient
service, allowing each child access to the services they require when most
needed. By keeping the low-vision assessment appointment open to other
professionals involved in the child's educational welfare, good communication
can be maintained, and a more multi-disciplinary service offered.
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JULIE LENNON
Department of Optometry and Paediatric Ophthalmology
Manchester Royal Eye Hospital
Oxford Road
Manchester
M13 9WH
United Kingdom
Email: Julie.Lennon@CMMC.nhs.uk