Prevalence of myopia among disadvantaged Australian schoolchildren

Authors: Aicun Fu(1), Kathleen Watt(2), Barbara M. Junghans(2), Androniki Delaveris(2), Fiona Stapleton(2)

  1. Department of Ophthalmology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
  2. School of Optometry and Vision Science, UNSW, Sydney, Australia

Date: August 2020

Reference: PLoS ONE 15(8): e0238122 (LINK)

Summary

This retrospective cross sectional analysis of disadvantaged Australian school children reveals:

  • Lower overall prevalence of myopia than emmetropia and hyperopia
  • Higher prevalence of myopia in older children
  • No change in overall myopia prevalence between 2014 and 2018, but double the prevalence when compared to study data from 1976

Clinical relevance

  • The children included in this study were predominantly from rural areas which in comparison to children living in urban areas conceivably means:
    • Greater time spent outdoors
    • Less time spent on digital devices
    • Lower expectations from education
  • This research only captures data from a snapshot in time, however it reveals that while prevalence of myopia was higher in older compared to younger children as expected, myopia prevalence remained low, with most older children (14 & 15 yrs) being emmetropic.
  • Study outcomes add further weight to the suggestion that environmental factors such as outdoor lifestyle and early age educational pressures may have an impact on prevalence of myopia.

Limitations and future research

  • Non cycloplegic retinoscopy refraction was undertaken, which could potentially bias towards slightly more myopic refractions
  • The authors indicate that the measured lower prevalence of myopia, compared to that reported in studies on other Australian locations, suggests the need for including questions on socioeconomic status, education and outdoor activity in myopia prevalence studies.

Full story

Purpose

With the backdrop of increasing prevalence of myopia across East Asia being driven by increasing educational pressures and urbanisation, the authors sought to investigate prevalence of myopia amongst disadvantaged children predominantly living in rural New South Wales (NSW) and the Australian Capital Territory (ACT), Australia. This cohort, by virtue of rural location and in general having lower expectations from education, represent a contrasting demographic to the urbanised childhood populations with higher educational pressures, where myopia prevalence is reported to be increasing.

Study design

Retrospective analysis of records from vision examinations conducted at a children’s charity (Stewart House) located on the northern beaches of Sydney, Australia. Disadvantaged children from NSW and ACT are selected by principals from government schools to attend Stewart House for a period of 2 weeks during which eye screening examinations are conducted. 4365 children examined in 2014, 2016 and 2018 met the study criteria and were included in the study.

Measurement procedure

  • Non-cycloplegic retinoscopy while viewing a distance non-accommodative target
  • Classification (spherical equivalent):
    • Myopia: ≤-0.50D
    • Emmetropia: >-0.50D to +0.50D
    • Hyperopia: >0.50D
  • Comparisons were made to historical data measured at the same premises 40 yrs prior, however a different classification criteria was used to match the data analysis performed in the earlier study (spherical equivalent):
    • Myopia: <0.00D
    • Emmetropia: ≥0.00D to +1.25D
    • Hyperopia: >1.25D

Outcomes

Two thirds of children came from rural areas and the remainder from low-density housing.

  • Myopia: 4%
  • Emmetropia: 51.6%
  • Hyperopia: 44.3%

Change to prevalence from younger to oldest measured age groups:

  • Myopia increased gradually but remained low (2.5% to 7%)
  • Emmetropia increased from 38% to 54.8%
  • Hyperopia decreased from 59.5% to 38.2%
2020-09-08_15-44-54

Change in prevalence across different measurement years (2014 v 2016 v 2018) when considered across all participants:

  • Myopia did not significantly change (3.5%, 4.4%, 4.3%)
  • Emmetropia increased (33.3%, 57.8%, 64.9%)
  • Hyperopia decreased from (63.2%, 37.8%, 30.9%)

Comparison to 40 yr (1976) historical data:

  • Prevalence of myopia was higher in the current study (3.3% vs 7.4% in males, 3.8% vs 7.3% in females)
  • Prevalence of hyperopia was higher in the current study (7.1% vs 14% in males, 13.1% vs 19.8% in females)
  • Spherical equivalent refraction decreased with age and faster in females compared to males

Conclusions

  • Myopia prevalence in low socioeconomic Australian children increased with age, as expected, but remained at very low rates compared to that observed in urban areas
  • While mean spherical equivalent across all ages at each measurement year reduced between 2014 and 2018 there was no difference in prevalence of myopia across these timepoints
  • Prevalence of myopia was double to that measured 40 years prior but remained low at just over 7% in 14 & 15 year olds.

Abstract

Title: Prevalence of myopia among disadvantaged Australian schoolchildren: A 5-year cross-sectional study

Purpose Myopia prevalence is influenced by environmental factors including heritability and social disadvantage. The current prevalence of myopia among disadvantaged school children in Australia has not been reported. Therefore, this study analyses refractive data for children from rural and outer suburban areas.

Methods The records of 4,365 children aged 6–15 visiting a city-based government-school respite care center during the years 2014/2016/2018 were analyzed for right eye non-cycloplegic spherical equivalent refraction (SER). The prevalence of myopia (SER≤-0.50D) was compared with historical data.

Results The prevalence of myopia was 3.5%, 4.4% and 4.3% in 2014, 2016 and 2018, respectively. The prevalence of myopia increased with age (P<0.0001), but was not related to sex or year of testing (all P >0.05). The overall mean SER was 0.89±0.86D, 0.62±0.89D and 0.56±0.95 in 2014, 2016 and 2018, respectively. Mean SER was associated with year of testing, age (all P <0.0001) and sex (P = 0.03). Mean SER decreased slightly from 2014 to 2018 and demonstrated a significant shift towards less hyperopia with increasing age. Mean SER of females was higher than that of males and decreased faster than in males with age (P interaction = 0.03).

Conclusions Myopia prevalence increased with age. The mean SER decreased slightly from 2014 to 2018. Sex differences in the rate of change with age was observed. Compared with 40 years ago, the prevalence of myopia has doubled, but it remains significantly lower than in school children of a similar age living in established urban areas that are regarded as having a higher socioeconomic status.

Abstract link is here

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About Paul

Dr Paul Gifford is a research scientist and industry innovator based in Brisbane, Australia, and co-founder of Myopia Profile.

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