Ophthalmic Paediatrics and Genetics

ISSN: 0167-6784 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/iopg19

Normal values of visual acuity in children up to 13 years as assessed by the acuity card procedure A. J.F. Schenk-Rootlieb, O. Van Nieuwenhuizen, J. Van Zoggel, Y. Vander Graaf & J. Willemse To cite this article: A. J.F. Schenk-Rootlieb, O. Van Nieuwenhuizen, J. Van Zoggel, Y. Vander Graaf & J. Willemse (1992) Normal values of visual acuity in children up to 13 years as assessed by the acuity card procedure, Ophthalmic Paediatrics and Genetics, 13:3, 155-163, DOI: 10.3109/13816819209046484 To link to this article: http://dx.doi.org/10.3109/13816819209046484

Published online: 08 Jul 2009.

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Grating-acuity in children Normal values of visual acuity in children up to 13 years as assessed by the acuity card procedure

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A. J.F. SCHENK-ROOTLIEB’, 0. VAN NIEUWENHUIZEN’*, J. VAN ZOGGEL’, Y. VAN DER GRAAF2 and J.WILLEMSE*

’Department of Child Neurology, Wilhelmina Children’s Hospital, Utrecht; 21nstitute of Epidemiology, University of Utrecht; The Netherlands

ABSTRACT. The acuity card procedure proved to be a useful method for assessing visual acuity in children. Normal values of visual acuity measured by this method had already been assessed in children up to four years. To enable application of the test in older children this study obtained values in a group of 396 normal chiIdren, aged three months to 13 years. The mean curve as well as the 10th centile was calculated in different age groups. A considerable variation of acuity values causing a ‘dip’ in the 10th centile was found in the ages 18 to 24 months. A smaller ‘dip’ was found in the ages 48 t.0 52 months. This has to be attributed to behavioural properties connected with age. The results obtained in the group of children under four years of age corresponded fairly well with other studies. In schoolchildren a fair agreement could also be found between the data obtained using the acuity card procedure and the data obtained with the Landolt-C rings. Obtaining normal values for the acuity card procedure in children covering a wide age range facilitates recognition of visual handicap in children who are difficult to assess. Key words: grating acuity; acuity card procedure; normal values

INTRODUCTION Determination of visual acuity is part of the routine medical check-up of school-age children in The Netherlands. Using appropriate optotypes, e.g., letter cards, Landolt-C rings, Ehooks, it is easy to determine acuity and takes * Correspondence

fo: Dr. 0 . van Nieuwenhuizen, Department of Child Neurology, Wilhelmina Children’s Hospital, P.O. Box 18009, 3501 CA Utrecht, The Netherlands

only a few minutes. These methods cannot, however, be applied in children under three or four years of age, nor in many handicapped children. In such cases, one is confronted by a short attention span, easy fatiguability and speech or motor disorders which hamper the child’s capacity to express its perception. Hence, acuity is not measured as a matter of routine in children younger than three years nor in handicapped children. Many authors, however, stress the value of early assessment of acuity in this

Ophthalmic Puediutrics and Genetics - 1992, Vol13, NO. 3, pp. 155-163 0Aeolus Press Buren (The Netherlands) 1992

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A . J. F. Schenk-Rootlieb et al. group of children in order to adjust developmental stimulation should there be a visual deficit1‘8.Sonksen et ~ 1report . ~ a positive result of a developmentally based programme in severely visually impaired babies aged between oneand 13 months. Janetaf.5 describethevarious problems which may be encountered in the development of visually impaired children and ways of preventing them by adequate management. There are methods for determining acuity in younger children based on behavioural observations, e.g., with the Sheridan balls9. lo, but these are time consuming and cannot easily be used as screening methods in general practice. Moreover, this Sheridan ball method is based on detection of movement and not on resolution of individual elements in a repetitive pattern as used in other methods based on behavioural techniques, i.e., the forced choice preferential looking In this latter method, the same problems were initially encountered, but its modified version, the acuity card procedureI3-I5, is easier to apply and can be performed within a few minute^'^-'^. Various authors have used this method successfully in both normal children and children with neurological impairment 16-22. The acuity card procedure has now become the method of choice for assessing acuity in very young and retarded children. Normal values of this test were gathered in children aged one to four yearsZoand in small g r o ~ p s ~ ~To - *enable ~. use of the test in older handicapped children, normal values still have to be established for the older age group. The aim of the present study is to obtain normal values of grating-acuity in children covering the age-range three months to 13 years. The acuity values obtained by the acuity card procedure are compared with those determined using

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the Landolt-C rings in the children aged from four years upwards : this method is routinely performed in these children. SUBJECTS AND METHODS Between December 1988 and May 1990, a group of 401 infants, toddlers and schoolchildren was seen at their normal check-up at the child health care clinic or by the school doctor. Five infants were excluded because of prematurity and one because of Down’s syndrome. The ages of the 396 remaining children are shown in Figs. la, l b and lc. After obtaining informed consent from their parents, the visual acuity was determined using the acuity card procedure (see below). After the test, general medical and ophthalmological data as well as information regarding pregnancy, delivery and postnatal period were gathered from the children’s medical files. The acuity card procedure was applied as follows: The children were examined by a welltrained team in separate, adequately illuminated rooms (mean luminance level 200 lux) at the health care clinic or school. The patients were tested using a portable apparatus as described by McDonald eC ~ 1 . If~ the ~ . child was used to wearing spectacles, these were also worn during the examination. Special care was taken to attract and to sustain the child’s attention. The material used consisted of 15 grey cards (28 x 61 cm), each containing two circular targets (diameter 9.5 cm) 23 cm apart and a peephole in the middle. One of the circles shows a grating pattern, consisting of vertical black-and-white stripes of various widths, the other is a ‘blank one’, of equal luminance and consisting of a high frequency finely striped pattern beyond the normal resolution limit. The stripe width of the grating patterns varies from 0.19 to 24.12

Gruting-ucuity in children 25

N (11.137) '

I

Babies 20

15

10

5

0

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0

1

2

3

4

5

6

7

91011121314151617

B

Age in months N (n-110)

18

21

24

27

30

33

36

39

Age in %month

42

46

48

61

6 4 67-68

categories

(11.149) 50

Schoolchildren 40

30

20

10 0 1

6

7

a Ape

9

10

11

12

in years

Fig. I . Age distribution of normal children. a. Number of assessed infants aged 0-18 months (n = 137). b. Number of assessed children aged 18-60 months ( n = 110). c. Number of assessed children aged 5-13 years ( n = 149).

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A . J. F. Schenk-Rootlieb et al. cycleddegree if presented at a distance of 40 cm (i.e., Snellen equivalent 20/3200 to 20/23) or from 0.27 to 34.10 c/deg at a distance of 57 cm (i.e., Snellen equivalent 20/2200 to 20/17.5) in half octave steps. The cards are presented to the child through an opening in a screen of the same grey colour as the cards. The child is seated on a chair, or on its parent's lap at a distance of 57 cm in front of the screen (40 cm up to the age of six months). The test begins with the coarsest grating pattern. The observer, ignorant of the location of the grating pattern, judges the movement of the eyes through the peephole, then turns the card 180" and presents it again. If his judgement was correct, the next finest grating is presented; if not, the previous card is presented again. The procedure is continued until the finest grating that the child can discern correctly three times is determined. The entire procedure usually takes no more than five minutes. In the schoolchildren, acuity was not only assessed using the acuity card procedure, but also by the Landolt-C rings. This was performed by the school doctor and his assistant, trained in this method. The results obtained by the Landolt-C cards were considered normal if the child scored 0.8 (20/25, angular width 1.25 min) or more up to the age of six years, and 1 or more at the age of six years and older if tested at a distance of 5 m. Regarding statistical analysis, the relationship between the acuity and age was modelled by means of regression analysis (least-squares estimation) (SAS Institute Inc. 1985). After the modelling, several age-groups were formed. Below 18 months, the age-groups comprised three months, above the age of 18 months the age-groups comprised six months. Within each age-group, acuity was corrected for age according to the results of the regression analysis. Then 10th and 50th centiles were calculated in each

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age-group. RESULTS In the appendix, baseline characteristics of the children are summarized (insufficient anamnestic data were available for about 6% of the children). The success rate of applying the acuity card procedure proved to be very high: 99%. Problems such as sleepiness, crying and diversion of attention, could be solved in 12 infants. No values at all could be obtained in only four infants, ranging in age from 4 to 4.5 weeks, because of sleepiness. None of the older children failed, but problems in applying the acuity card procedure, again due to sleepiness and diversion of attention, were encountered in 13 toddlers. The relationship between acuity and age was well described by a multiple linear regression model, in which visual acuity was the outcome variable, while age and the square root of age were used as the independent variables. The model equation was : acuity = intercept + P I age + P2 age2 The regression analysis yielded the following results : intercept = 5.33 regression coefficient for age PI = 0.44 regression coefficient for the square root of age P2 = - 0.00062 1. The model shows a good degree of fit. Fig. 2 illustrates the fitted curve and the 10th centile. For reasons of comparison with other studies, the same results are presented on a logarithmic scale in Fig. 3. The 10th and 90th centiles have also been plotted. In 152 of 396 (39%) children, the results of assessing the acuity using the acuity card procedure could be compared with those obtained by the Landolt-C cards (Table 1). Normal Landolt values and acuity card-values above the 10th

Grating-acuity in children Snellen equivalent

ycles/degree

60

60

2.6

2

40

1.5

30 1

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20

D.5

10

0' 0

3

I

I

I

50

100

150

200

age in months Fig. 2. Acuity as assessed by acuity card procedure. cycles/degree

P90 curve'

1' 0

I

I

I

I

50

100

150

200

age in months Fig. 3 . Acuity as assessed by acuity card procedure (logarithmic).

centile were seen in 140 of 152 (92%) children. Two children scored low with both methods. In four a low value on the acuity cards but normal Landolt-value was found : of these four, one child was hypermetropic, no abnormalities were reported in the other three. In six children a

normal value with the acuity cards but a low Landolt value was found ; one of these children was myopic, two children had been treated for squint and in three children no information was available.

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A . J . F. Schenk-Rootlieb et al.

test period lasting only a few minutes can be too long. This also explains the large variation of values in this age group as can be seen in Landolr-C cards Visual acuity cards Figs. 2 and 3. A similar phenomenon at the ages low V . U . normal v.a. total of about 48 to 52 months may be attributed to a certain shyness of young children who have just low v.a. 2 6 8 entered school. The steep rise of the curve within normal v.a. 4 140 144 the first year of life is conspicuous. This is caused by the rapid development of acuity in the DISCUSSION first year of life, attributed to physiological changes such as foveal differentiation, myelinaThe acuity card procedure proved to be a useful tion and formation of synapses18. In the older and convenient method for assessing acuity in age groups, a flattening of the curve is seen, and children. It is well tolerated and many children the 50th centile is influenced by a few high even find it amusing. The success rate in o u r scores in a relatively small number of children. The literature does contain results of acuity study was 99%. The literature also reports success rates from about 80 to assessments using this method in infants and 9 9 . 5 ~ ~14,19,20.23. 3, children up to four years. Dobson used this It is important, however, that the child is method to examine 66 children aged 16 days to attentive and not too tired or sleepy. Testing 32 monthsI4 as well as ten healthy neonate^'^, may be difficult in children in the age group 18 McDonald et a/. examined 36 normal children, to 36 months, as seen e l s e ~ h e r e ~In . ~ these ~. aged 18, 24, 30 and 36 months2'. Van Hof-van children, attention is easily diverted and even a Duin and Mohn assessed 91 fullterm and 36 pre-

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TABLE I . Comparison visual acuity obtained by Landolr-C cards and visual acuity cards ( n = 152)

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Grating-acuity in children term infants in the first year of life25.Heersema analysed the visual development of 210 children aged one to four years with the acuity card procedure20. Courage and Adams tested 140 infants and children from birth to three years using the acuity card procedure29. Fig. 4 compares the results of former studies, as compiled by Courage and ad am^^^, with those of this study regarding children under the age of four years. One should be aware that the time basis in Fig. 4 is different from that in Figs. 2 and 3 . The results are found to correspond fairly well. It is feasible that data obtained in older children in this study also prove reliable. Comparison between two techniques of assessing visual acuity was possible in the group of schoolchildren as they were routinely assessed by Landolt-C rings. There appears to be a fair degree of overall agreement as far as normal values are concerned (Table 1). The cause of the divergence of the values in ten children is not clear. In some cases, amblyopia may have been of some importance, but too few precise data were available to justify a fair judgement. Concerning the data of assessment of visual acuity by the two techniques mentioned above, one has to take into account that different methods of assessment measure different 'types

of acuity'. Kennard and Clifford Rose defined visual acuity as a measure of the capacity to resolve small detail at high contrast30. The method of measuring acuity by Landolt-C rings is based on the recognition of fine details in a target, the assessment by acuity cards as resolution of elements in a repetitive pattern. Van Hof-van Duin stresses the difficulties in comparing recognition acuity with detection and resolution acuities, since other areas of the brain, such as the parietal and temporal cortex are functionally involved in identification and recognition of spatial details2*. The Committee on Vision recommends the Landolt-C ring as the primary standard optotype in its report on standard procedures of the clinical measurement and specification of visual acuity3'. As discussed before however, the Landolt-C rings cannot be used in children beneath the age of four years and are difficult to use in many mentally and physically handicapped children. In these children the acuity card procedure is a useful substitute. ACKNOWLEDGEMENTS The authors are greatly indebted to their colleagues Mrs S. F. Faber-Woud, B. van Halsema and C . P . E . Brouwer and nurse R . Huiden for their help in collecting the test results.

APPENDIX. Baseline characteristics of the assessed children (n = 396) Pregnancy:

Birth:

Birth weight:

n o problems toxicosis twins other problems unknown

318 17 21 24

80% 4 qo 3 90 7 70 6 To

a terme premature ( < 3 8 wks gest.) overdue ( > 4 2 wks gest.) unknown

352 16

89% 4 '70

5

1 Yo

23

6 To

normal small for date unknown

34 I 32 23

86% 8 '70 6 Yo

10

161

A . J. F. Schenk-Rootlieb et at. ~

Perinatal problems:

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Congenital abnormalities:

Medical problems:

*

no problems caesarian section other artificial delivery breech position problems of the child unknown

254 32 23 6 61 25

63 70

no abnormalities orthopaedic problem cardiac problem urogenital problem minor malformations diverse anomalies unknown

344 15 8 4 2 5 19

87% 4% 2 Yo I vo

no problems ophthalmological problems otological problems chron.respir.problems (atopia) speech problems motor problems other problems unknown

307 44 32 20 9 3 4 14

71% 10% 7 "70 5% 2 To

*Ophthalmological problems of the assessed children (n = 44) squint refraction anomaly conjunctivitis/dacryostenosis nystagmus coloboma low vision one eye

8v o 6 Yo

1 vo 15 V o 6 To

I070 1V O

5 010

Ivo I To

3 Yn

28 10 2 2 1

1

REFERENCES 1. Warburg M, Frederiksen P , Rattlef 1. Blindness among 7700 mentally retarded children in Denmark. I n : Clinics in Developmental Medicine. Smith V, Keen J , editors. Philadelphia : Spastics International Medical Publications, 1979. 2. Dholakia S. The apptication of a comprehensive visual screening. Ophthalm Physiol Optics 1987. 3. Fielder AR, Moseley MJ. Do we need to measure the vision of children? J Roy SOCMed 1988; 81 :380-383. 4. Hullo A. Le depistage des troubles visuels chez le nouveau-ne et I'enfant. Pediatrie 1989; 44:113-120. 5 . Jan JE, Sykanda A, Ciroenveld M. Habilitation and rehabilitation of visually impaired and blind children. Pediatrician 1990 ; 17 :202-207. 6. Sonksen P , Petrie A, Drew KJ. Promotion of visual development of severely visually impaired babies: evaluation of a developmentally based programme. Devel Med Child Neurol 1991 ; 33 : 320-335. 7 . Hall DMB, Hall SM. Early detection of visual defects in infancy. Br Med J 1988; 296:823-824. 8 . Romano PE. Advances in vision and eye screening: screening at six months of age. Pediatrician 1990; 17: 134-141. 9. Sheridan MD. The Stycar graded-balls vision test. Devel Med Child Neurol 1973 ; 15 : 423-432. 10. Loewer-Sieger L, Wenniger-Prick L, Lantau VK. Vroegtijdige onderkenning van visuele stoornissen bij het jonge kind. Ned Tschr Geneesk 1987 ; 49 : 13 1. 11. Teller DY, Morse R, Borton R, Regal D. Visual acuity for vertical and diagonal gratings in human infants. Vision Kes 1974; 14: 1433-1439. 12. Atkinson J , Braddick 0. New techniques for assessing vision in infants and young children. Child Care Hlth Devel 1979; 5:389-398. 13. Dobson V, McDonald MA, Teller DY. Visual acuity of infants and young children: forced-choice prefcrential looking procedures. Am Orthopt J 1985; 35: 118-125.

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Grating-acuity in children 14. Dobson V, McDonald MA, Kohl P, Stern N, Samek M, Preston K. Visual acuity screening of infants and young children with the acuity card procedure. J Am Optom Ass 1986; 27:284-289. 15. Dobson V, Schwartz TL, Sandstrom J , Michel L. Binocular visual acuity of neonates: the acuity card procedure. Devel Med Child Neurol 1987; 29: 199-206. 16. Teller DY, McDonald MA, Presonk K, Sebris SL, Dobson V. Assessment of visual acuity in infants and children: the acuity card procedure. Devel Med Child Neurol 1986; 28: 779-789. 17. Mohn G, Van Hof-Van Duin J . Rapid assessment of visual acuity in infants and children in a clinical setting using acuity cards. Doc Ophthalmol Proc Series 1986; 45 : 363-372. 18. Hertz BG. Acuity card testing of retarded children. Behav Brain Res 1987; 24:85-92. 19. Hertz BG, Rosenberg J, Sjo 0, Warburg M. Acuity card testing of patients with cerebral visual impairment. Devel Med Child Neurol 1988; 30:632-637. 20. Heersema DJ. Perinatale Risicofactoren en Visuele Ontwikkeling bij Jonge Kinderen. Rotterdam : Universiteitsdrukkerij Erasmus, 1989. 21. Kohl P , Samek BM. Refractive error and preferential looking visual acuity in infants 12-24 months of age: year 2 of a longitudinal study. J Am Optom Ass 1988; 59:686-690. 22. Van Hof-Van Duin J. The development and study of visual acuity. Devel Med Child Neurol 1989; 31 :543-552. 23. McDonald MA, Ankrum C, Preston K, Sebris SL, Dobson V. Monocular and binocular acuity in 18-36 month olds: acuity card results. Invest Ophthalmol Vis Sci 1985; 308. 24. McDonald MA, Sebris SL, Mohn G, Teller DY, Dobson V. Monocular acuity in normal infants: the acuity card procedure. Am J Optom Physiol Opt 1986; 63: 127-133. 25. Van Hof-Van Duin J , Mohn G. The development of visual acuity in normal fullterm and preterm infants. Vision Res 1986 ; 26 :909-91 6. 26. SAS Institute Inc, 1985. 27. Heersema DJ, Van Hof-Van Duin J. Gedragsmatige bepa!ing van de gezichtsscherpte bij kinderen van 1 tot 4 jaar. Tschr Kindergeneesk 1985; 57:210-214. 28. Atkinson J. Human visual development over the first 6 months of life. A review and a hypothesis. Human Neurobiol 1984; 2:61-74. 29. Courage ML, A d a m J. Visual acuity assessment from birth to three years using the acuity card procedure: crossselectional and longitudinal samples. Optom Vision Sci 1990; 9:713-718. 30. Kennard C, Clifford Rose F. Psychological aspects of clinical neuro-ophthalmology. Concluding remarks. London : Rose 1988. 31. Committee on Vision. Report of Working group 39. Recommended standard procedures of the clinical measurement and specification of visual acuity. Adv Ophthalmol 1980; 41 : 103-148.

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Grating-acuity in children. Normal values of visual acuity in children up to 13 years as assessed by the acuity card procedure.

The acuity card procedure proved to be a useful method for assessing visual acuity in children. Normal values of visual acuity measured by this method...
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