New Zealand Vision & Hearing Screening Report 2005/06
ISSN 1173-597X
New Zealand Vision and Hearing Screening Report
July 2005 – June 2006
Report prepared by Greville Consulting for
National Audiology Centre
Auckland District Health Board
December 2006
CONTENTS
SUMMARY
INTRODUCTION
COVERAGE
New school entrants
Preschoolers
Coverage and ethnicity
FAILURE RATES
HEARING
New School Entrants
3-year-old tympanometry
Ethnicity
Historical comparison
VISION
New school entrants
Preschoolers
Year 7 (11-year-olds)
Ethnicity
ACKNOWLEDGMENT
SUMMARY
COVERAGE
New School Entrants
The overall national estimated coverage rate was 99% relative to the cohort estimate derived from the numbers of children enrolled in schools. Overall in 2005/0660,094new entrants had their hearing screened and marginally more (60,466) were screened for vision.
Preschoolers
The overall national estimated coverage rate for three-year-olds screened on tympanometry was 86%, a total number of46,226.
Coverage of 4-year-olds for vision screening was less complete – 34,930 children were screened - a national coverage rate of 65%. The lower coverage is due to Auckland and Counties Manukau District Health Boards refraining from screening this group of children.
REFERRAL RATES
New School Entrants
The overall audiometry referral rate for new entrants in 2005/06 was estimated at 6.6%. This is fairly low compared with results collected since 1991. Over the last three years, the failure rate has plateaued.
The overall vision screening failure rate for new entrants was 3.2%.
Preschoolers
The overall referral rate for three year old tympanometry was 6.4%, also showing a reduction from levels found previously.
3.1% of 4-year-olds screened for vision failed the screening test.
Year 7
The failure rate for vision screening of Year 7 children was 4.7%.
ETHNIC GROUP DIFFERENCES
New School Entrants
The reduction in audiometry failure rates over the last 15 years was evident in all ethnic groups. PacificIslandchildren had the highest failure rate – 11.2% (cf 10.3% for Maori children, and around 4% for all other groups).
Ethnic differences were not so marked with vision screening – there were higher failure rates for Asian and Maori children at new entrant level, but only for acuity test (4.4% and 4.2% respectively, cf rates of around 3% for other ethnic groups).
Preschoolers
Coverage of Maori and PacificIslandpreschool children was lower than for other ethnic groups – this effect being particularly marked for vision screening.
PacificIsland children remain the group with the highest tympanometry failure rate as preschoolers (13.2%, cf Maori children 10.0%, and other ethnic groups around 4-5%).
Maori and Asian children showed marginally higher failure rates on vision screening (both 3.7% cf 2-3% for other ethnic groups).
Year 7 Vision screening
The failure rate for Asian children at this age group was more dramatic – 8.7%, cf rates around 3-4% for all other ethnic groups.
REGIONAL VARIATION IN REFERRAL RATES
New Entrants
Ten District Health Boards reportedaudiometry referral rates of 5% or less – although in six cases, there was reason to doubt the validity of their results. One(HawkesBay) recorded a new entrant referral rate over 10%.
Three Year Olds
EightDistrict Health Boards achieved tympanometry referral rates under 5% for three year olds. The highest referral rates for this age-group were Tairawhiti, Waikato, Wanganui and Counties Manukau, all with rates exceeding 10%.
INTRODUCTION
District Health Boards across New Zealand provide or purchase services to screen the vision and hearing of children. The screening programmes are carried out according to nationally agreed protocols[1].
Hearing
Tympanometry screening is carried out on preschool children – predominantly 3-year-olds, in an attempt to identify chronic middle ear disease so that it can be treated before children start school. Children who fail the initial test are retested on the next visit by the technicians, and if they fail the screening test again, they are referred for treatment.
New entrant school children (ie 5-year-olds) are tested on both pure tone audiometry and tympanometry. Audiometry is a more direct measure of hearing, but it can be less reliable in the noisy test conditions frequently found in schools. The combination of tests ensures more valid identification of children with hearing loss and/or ear disease. For this age-group also, in most cases referral is not made until tests have been failed on two consecutive test occasions.
Vision
The purpose of vision screening is to detect the need for refractive correction at an age where:
- amblyopia may be treatable (younger children) and
- the incidence of myopia increases (older children)
Vision is screened for preschoolers at the age of 4 years. At this age, tests are carried out for distance visual acuity (the Parr letter matching test) and squint.
New school entrants are tested on the 4-meter Parr letter-matching test with crowding for acuityand thePenlight reflection test/cover test for squint.
Year 7 children are screened with the Snellen eye chart test for acuity, and boys are screened for colour vision with the Isihara colour vision test.
The two main features that can be extracted from the data available concern coverage of the population, and failure rates.
In most areas, separate data are kept for children of four main ethnic groups – Maori, PacificIsland, European/Pakeha, and Asian groups. In addition there is an Other grouping. Where ethnic data are not kept, all data are presented in the Other grouping.
COVERAGE
New school entrants
Total numbers tested within each region are presented in Table 1, together with the population figures. These are derived from the numbers of children enrolled in primary schools within each educational region as at July 2005. Note that they are estimates only – and the assumption has been made that there are equal numbers of children in each year of primary schooling. In some areas with changing populations this may not be a valid assumption. Moreover, timetabling of visits to schools also introduces variability, since the statistical year is July – June, and the screening programme is normally planned by calendar year.
Coverage rates for hearing vary from 85 – 114%, with a national average of 99%. For vision screening, the range was 79 - 114%
Table 1. Coverage of new entrant screening by educational region
Educational region / Enrolments / HearingTested / Hearing
Coverage / Vision tested / Vision coverage
Northland / 2,383 / 2,209 / 93% / 2,209 / 93%
Auckland / 20,097 / 21,379 / 106% / 22,911 / 114%
Waikato / 5,952 / 5,041 / 85% / 5,165 / 87%
Bay of Plenty / 4,100 / 4,692 / 114% / 4,590 / 112%
Tairawhiti / 790 / 861 / 109% / 849 / 108%
HawkesBay / 2,458 / 2,455 / 100% / 2,344 / 95%
Taranaki / 1,624 / 1,667 / 103% / 1,430 / 88%
Manawatu-Wanganui / 3,400 / 3,182 / 94% / 3,022 / 89%
Wellington / 6,351 / 6,377 / 100% / 6,149 / 97%
Nelson Marlborough / 1,827 / 1,667 / 91% / 1,609 / 88%
West Coast / 420 / 373 / 89% / 362 / 86%
Canterbury / 7,169 / 6,754 / 94% / 6,620 / 92%
Otago / 2,470 / 2,160 / 87% / 1,940 / 79%
Southland / 1,361 / 1,277 / 94% / 1,266 / 93%
National / 60,404 / 60,094 / 99% / 60,466 / 100%
Preschoolers
Preschool population numbers are estimated from census data.
Tympanometry screening coverage varies from 57% to 117%, with a mean of 86%. Note that coverage may vary because of timetabling issues.
Table 2. Coverage of 3-year-old tympanometry screening by health region
DHB region / Population / Tested / CoverageNorthland / 2,117 / 1,390 / 66%
Waitemata / 6,248 / 4,999 / 80%
Auckland / 4,928 / 3,684 / 75%
Counties Manukau / 6,596 / 5,863 / 89%
Waikato / 4,887 / 3,594 / 74%
Bay of Plenty / 2,650 / 2,324 / 88%
Lakes / 1,589 / 1,341 / 84%
Tairawhiti / 756 / 694 / 92%
HawkesBay / 2,172 / 2,228 / 103%
Taranaki / 1,453 / 1,110 / 76%
MidCentral / 2,198 / 1,833 / 83%
Wanganui / 948 / 543 / 57%
Wairarapa / 539 / 384 / 71%
Hutt / CapitalCoast / 5,438 / 5,301 / 97%
Nelson Marlborough / 1,582 / 1,849 / 117%
West Coast / 388 / 425 / 110%
Canterbury / 5,470 / 5,350 / 98%
South Canterbury / 659 / 461 / 70%
Otago / 1,999 / 1,866 / 93%
Southland / 1,418 / 987 / 70%
National / 53,496 / 46,226 / 86%
The overall visual acuity screening coverage rate for 4-year olds was 65%, with a range of 0 – 115%. The main contributor to the lower coverage for vision as opposed to tympanometric screening was the policies of Auckland and Manukau Counties DHBs to refrain from screening this group.
Table 3. Coverage of 4-year-old vision screening by health region
DHB region / Population / Tested / CoverageNorthland / 2,117 / 1,620 / 77%
Waitemata / 6,248 / 4,447 / 71%
Auckland / 4,928 / 172 / 3%
Counties Manukau / 6,596 / 0 / 0%
Waikato / 4,887 / 3,747 / 77%
Bay of Plenty / 2,650 / 2,293 / 87%
Lakes / 1,589 / 757 / 48%
Tairawhiti / 756 / 758 / 100%
HawkesBay / 2,172 / 2,027 / 93%
Taranaki / 1,453 / 974 / 67%
MidCentral / 2,198 / 1,951 / 89%
Wanganui / 948 / 290 / 31%
Wairarapa / 539 / 514 / 95%
Hutt / CapitalCoast / 5,438 / 4,585 / 84%
Nelson Marlborough / 1,582 / 1,032 / 65%
West Coast / 388 / 290 / 75%
Canterbury / 5,470 / 6,298 / 115%
South Canterbury / 659 / 451 / 68%
Otago / 1,999 / 1,627 / 81%
Southland / 1,418 / 1,097 / 77%
National / 54,035 / 34,930 / 65%
Coverage and ethnicity
Analysis of coverage by ethnicity showed that European/Pakeha children were more likely than children from other ethnic groups to be screened as 3-year-olds (see Figure 1). Coverage rates for tympanometry ranged from 88% for European/Pakeha children to 65% for Maori children. These rates reflect differential uptake of preschool education.
Figure 1. National preschool coverage rates by ethnicity for tympanometry and vision screening.
There was an even greater ethnic difference in coverage for vision screening than for tympanometry – the European/Pakeha coverage rate was 77%, but the Pacific rate was 29%. Afactorin this poor coverage is lack of screening being carried out in areas of high density for Maori and Pacific people (ie Auckland and Counties Manukau districts).
FAILURE RATES
HEARING
New School Entrants
Two types of failure data are available for hearing screening of new school entrants – firstly those who failed pure tone audiometry (regardless of tympanometric result), and secondly, the audiometry failures combined with those who failed tympanometry only.
A failure on pure tone audiometry is defined as:
- At least two thresholds 45 dB or greater (this results in immediate referral to audiology services if tympanometry is normal, or to the GP or specialist ear nurse if tympanometry is abnormal)
- At least one threshold exceeding the screening levels of 30 dB (500 Hz) or 20 dB (1000 – 4000 Hz) – this results in the child being scheduled for a retest at the next visit (in 10-16 weeks time).
Tympanometry is failed if the tympanogram is flat. A flat tympanogram combined with an abnormal ear canal volume results in immediate referral to the GP or ear nurse. A child with a flat tympanogram but normal ear canal volume is scheduled for a retest at the next visit. A repeated tympanometric failure in the same ear/s results in referral to the GP or ear nurse.
Nationally, the audiometric failure rate was estimated at 6.6%, with a combined failure rate (ie failure on audiometry and/or tympanometry) of 8.5%.
There was regional variation in failure rates from 1.0 – 10.8% (see Table 4 and Figure 2), although the rates below 3% are probably invalid and have been discounted for calculation of the national failure rates. The trend was for failure rates to be higher in the more northern areas of the country.
Table 4 New entrant audiometry failure numbers and rates by health region
DHB region / Tested / Failed / Failure rateNorthland / 2,209 / 183 / 8.3%
Waitemata / 6,530 / 655 / 10.0%
Auckland / 6,284 / 313 / 5.0%
Counties Manukau / 8,565 / 523 / 6.1%
Waikato / 5,041 / 348 / 6.9%
Bay of Plenty / 3,326 / 84 / 2.5%
Lakes / 1,366 / 24 / 1.8%
Tairawhiti / 861 / 46 / 5.3%
HawkesBay / 2,455 / 264 / 10.8%
Taranaki / 1,667 / 59 / 3.5%
MidCentral / 2,399 / 174 / 7.3%
Wanganui / 783 / 17 / 2.2%
Wairarapa / 519 / 8 / 1.5%
Hutt / CapitalCoast / 5,858 / 56 / 1.0%
Nelson Marlborough / 1,667 / 65 / 3.9%
West Coast / 373 / 23 / 6.2%
Canterbury / 6,135 / 331 / 5.4%
South Canterbury / 619 / 55 / 8.9%
Otago / 2,160 / 80 / 3.7%
Southland / 1,277 / 59 / 4.6%
National / 59,575 / 3,367 / 6.6%
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New Zealand Vision & Hearing Screening Report 2005/06
Figure 2. New entrant hearing failure rates by health region
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New Zealand Vision & Hearing Screening Report 2005/06
3-year-old tympanometry
Preschool tympanometry failure rates for each district are shown in Figure 3. The national failure rate for 3-year-olds was 6.4%, with a range of 0.6% to 11.8%.
Ethnicity
Ethnic variation in both new entrant and preschool hearing failure rates is shown in Figure 4. At both the preschool and new entrant levels, PacificIsland children had the highest failure rates (12.2% and 16.5% respectively), closely followed by Maori children (10.7% and 14.1%).
Historical comparison
The national audiometry failure rate of 6.6% compares favourably with failure rates found in earlier years. An historical comparison is shown in Figure 5. This shows a downward trend over the last 15 years, with a slight improvement in 2004/05.The 2005/06 results indicate a plateauing effect.
Nationally, there appears to have been a slight reduction in the number of children with ear problems affecting their hearing. (see Figure 5).
New entrant audiometry failure rates over time are given for each health region in Table 5.
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New Zealand Vision & Hearing Screening Report 2005/06
Figure 3. 3-year-old tympanometry failure rates by health region
Figure 4. Hearing failure rates for different measures by ethnicity
Figure 5. National new entrant audiometry failure rates from 1991 to the present by ethnicity
Table5. New entrant audiometry failure rates (%) for 1992/93 – 2005/06for each health region
DHB region / 92/93 / 93/94 / 94/95 / 95/96 / 96/97 / 97/98 / 98/99 / 99/00 / 00/01 / 01/02 / 02/03 / 03/04 / 04/05 / 05/06Northland / 15.9 / 12.7 / 12.1 / 12.9 / 12.9 / 14.2 / 11.5 / 13.7 / 15.3 / 14.5 / 12.8 / 8.0 / 9.9 / 8.3
Waitemata / 10.0 / 7.0 / 8.0 / 7.4 / 7.0 / 8.5 / 7.6 / 5.5 / 6.6 / 6.7 / 6.6 / 7.6 / 1.5 / 10.0
Auckland / 7.5 / 8.5 / 9.6 / 8.5 / 6.8 / 8.1 / 6.6 / 6.5 / 6.0 / 8.5 / 5.8 / 6.1 / 4.9 / 5.0
Counties Manukau / 14.4 / 12.8 / 12.4 / 14.9 / 12.6 / 8.6 / 9.6 / 12.0 / 5.7 / 14.3 / 14.2 / 11.0 / 5.4 / 6.1
Waikato / 9.1 / 7.9 / 8.1 / 9.0 / 7.7 / 8.6 / 8.2 / 8.5 / 8.8 / 8.7 / 9.1 / 7.8 / 8.3 / 6.9
Bay of Plenty / 13.1 / 8.7 / 6.3 / 5.6 / 3.8 / 12.5 / 12.0 / 7.2 / 5.9 / 10.5 / 10.0 / 3.8 / 0.5 / 2.5
Lakes / 7.4 / 9.3 / 11.0 / 7.8 / 4.2 / 9.7 / 10.3 / 6.9 / 5.2 / 5.2 / 4.9 / 3.5 / 1.7 / 1.8
Tairawhiti / 8.3 / 12.0 / 17.7 / 7.0 / 7.8 / 7.4 / 6.5 / 3.7 / 3.9 / 10.3 / 10.8 / 4.9 / 6.7 / 5.3
HawkesBay / 12.8 / 8.3 / 6.4 / 5.7 / 7.4 / 9.9 / 9.9 / 13.1 / 11.3 / 9.3 / 9.9 / 4.9 / 9.6 / 10.8
Taranaki / 4.0 / 6.3 / 9.2 / 7.2 / 5.9 / 6.2 / 6.2 / 6.6 / 8.1 / 11.7 / 10.5 / 9.2 / 1.6 / 3.5
MidCentral / 8.1 / 7.6 / 6.2 / 7.3 / 5.6 / 5.9 / 5.7 / 4.9 / 4.4 / 6.1 / 5.1 / 6.9 / 8.0 / 7.3
Wanganui / 9.3 / 14.3 / 8.2 / 7.7 / 2.8 / 5.1 / 3.4 / 1.0 / 0.3 / 1.5 / 2.0 / 2.5 / 2.2 / 2.2
Wairarapa / 6.1 / 4.4 / 8.6 / 14.2 / 8.2 / 19.5 / 0.5 / 6.3 / 10.4 / 2.8 / 2.5 / 5.1 / 4.2 / 1.5
Hutt / CapitalCoast / 10.2 / 8.5 / 6.7 / 5.5 / 14.1 / 7.5 / 4.4 / 10.4 / 3.3 / 5.7 / 5.2 / 1.2 / 1.0 / 1.0
Nelson Marlborough / 6.2 / 7.7 / 6.8 / 5.8 / 6.0 / 6.5 / 4.8 / 0.7 / 6.7 / 6.9 / 7.7 / 7.6 / 3.6 / 3.9
West Coast / 6.9 / 7.8 / 10.2 / 7.9 / 7.1 / 5.6 / 4.7 / 4.2 / 1.6 / 9.1 / 10.9 / 8.0 / 3.5 / 6.2
Canterbury / 10.5 / 6.8 / 5.9 / 6.6 / 6.4 / 6.5 / 5.7 / 5.1 / 5.0 / 5.5 / 5.2 / 4.7 / 4.8 / 5.4
South Canterbury / 9.3 / 3.1 / 4.7 / 2.2 / 6.4 / 12.5 / 10.3 / 7.6 / 6.0 / 6.4 / 9.1 / 9.5 / 9.2 / 8.9
Otago / 12.0 / 9.0 / 3.7 / 7.0 / 9.6 / 4.7 / 4.6 / 5.8 / 3.1 / 3.6 / 3.5 / 3.1 / 0.7 / 3.7
Southland / 9.2 / 7.0 / 6.2 / 6.4 / 6.7 / 10.5 / 9.6 / 6.8 / 8.5 / 8.2 / 10.0 / 6.0 / 3.7 / 4.6
National / 9.7 / 8.8 / 8.3 / 8.5 / 8.4 / 8.6 / 7.7 / 7.7 / 6.7 / 7.8 / 8.1 / 6.5 / 6.3 / 6.6
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New Zealand Vision & Hearing Screening Report 2005/06
VISION
New school entrants
Failure rates by District Health Board for the various test combinations available for new entrants are shown in Figure 6.
Nationally, 3.2% of new entrants failed one or both vision screening tests. District failure rates ranged from 2.1%to 11.4%. Overall, 2.9% of new entrant children failed the Parr test, and 0.9% failed the cover test for squint. 0.6% failed both tests.
Preschoolers
Failure rates by District Health Board for 4-year-olds are shown in Figure 7.
Nationally, 3.1% of preschoolers failed the vision screening test. District failure rates ranged from 0.4% to 8.7%.
Year 7 (11-year-olds)
Failure rates by District Health Board for Year 7 children are shown in Figure 8.
Nationally, 4.7% of Year 7 children failed the vision screening test. District failure rates ranged from 0.8% to 11.7%.
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New Zealand Vision & Hearing Screening Report 2005/06
Figure 6. New entrant vision screening failures by health region
Figure 7. 4-year-old vision screening failure rate by health region
Figure 8. Year 7 vision screening failure rate by health region
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New Zealand Vision & Hearing Screening Report 2005/06
Ethnicity
Failure rates for the three cohorts of vision screening by ethnic group are shown in Figure 9.
Relatively little ethnic variation is evident from these data, apart from a slightly higher failure rate on acuity tests for Asian children (3.7% for 4-year-olds and 4.4% for new entrants), rising to a significantly higher rate by Year 7 (8.7%). Maori children tend to have a higher failure rate as preschoolers (3.7%).
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New Zealand Vision & Hearing Screening Report 2005/06
Figure 9. National failure rates for vision screeningfor different cohorts by ethnicity
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New Zealand Vision & Hearing Screening Report 2005/06
ACKNOWLEDGMENT
Thanks are due to the Vision Hearing Technicians, Public Health Nurses and their managers across New Zealand, for their cooperation in collecting and contributing their data.
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[1] Wellchild - Tamariki Ora. Ministry of Health, 2002