The impact of hyperopia on academic performance among children: a systematic review

Authors: Mavi S, Chan VF, Virgili G, Biagini I, Congdon N, Piyasena P, et al.

Geographical coverage: worldwide    

Sector: Burden of disease

Sub-sector: Epidemiology

Equity focus: Children

Study population: Children aged 4-17

Review type: Other review

Quantitative synthesis method: Meta-analysis and narrative review.

Qualitative synthesis method: Qualitative analysis undertaken of studies not included in meta-analysis.

Background: Hyperopia is common in young children. Research has underscored the connection between uncorrected hyperopia, near visual function and early literacy development, reading speed and academic achievement in children. However, no systematic review or meta-analysis of the impact of hyperopia on children’s academic performance has been published or registered to date.

Objectives: To assess the impact of uncorrected hyperopia and hyperopic spectacle correction on children’s academic performance.

Main findings:

In summary, evidence generated from this review indicates that uncorrected hyperopia is associated with poor academic performance.

The review incorporated 25 selected studies, which consisted of 21 observational studies (16 cross-sectional, three longitudinal, and two case-control studies) and four interventional studies (one cross-sectional and three longitudinal intervention studies). The majority (22) of these studies were conducted in high-income countries. These 25 studies encompassed 23,883 school children aged between 3 and 17 years, spanning 12 countries. The gender distribution varied from 34.3% to 63.0% males. Fourteen studies (56.0%) did not disclose the gender distribution of participants. The studies were carried out in various settings such as schools, communities, or health care facilities, while one study did not specify the setting. Out of the studies included, the authors classified three as high quality, while 88% were deemed to be of low to moderate quality.

Based on the meta-analyses, authors reported a small but significant adverse effect on educational performance in uncorrected hyperopic compared to emmetropic children {SMD-0.18 [95% confidence interval (CI), -0.27 to -0.09]; p <0.001, four studies} and a moderate negative effect on reading skills in uncorrected hyperopic compared to emmetropic children [SMD -0.46 (95% CI, -0.90 to -0.03); p ¼ 0.036, three studies]. Authors also found reading skills were significantly worse in hyperopic than myopic children [SMD 0.29 (95% CI, 0.43 to 0.15); p <0.001, one study]. Based on the qualitative analysis on 10 of 19 studies excluded from meta-analysis, authors report a significant (p <0.05) association between uncorrected hyperopia and impaired academic performance. It was observed that two interventional studies found hyperopic spectacle correction significantly improved reading speed (p <0.05).

In the leave-one-out sensitivity analyses conducted, the removal of most studies unsurprisingly rendered the nonsignificant pooled ES estimate due to loss of precision, considering the small number of studies in each meta-analysis.

Given the limitations of current methodologies, authors note that further research is needed to evaluate the impact on academic performance of providing hyperopic correction. A full-scale randomised clinical trial is needed to determine the causal association between hyperopic correction and academic performance. A further issue that remains unresolved is whether correction of hyperopia restores academic performance. Although the majority of studies have used different refractive groups as comparators, comparison between uncorrected and corrected hyperopic groups would provide valuable insights as to whether the correction of hyperopia contributes to improved academic performance in children.

Methodology:

The review included studies of any language, publication date, or location; primary investigations and reviews; observational or interventional studies. Participants were school-going children and adolescents aged 4-17 years diagnosed with uncorrected hyperopia of any degree, with or without astigmatism, but without ocular comorbidities like strabismus and amblyopia. Studies with mixed participant groups not reporting separate data for these participants were excluded. The primary outcome was academic performance, assessed through standardised or non-standardised testing or teachers’ evaluations. Studies relying solely on child self-reported performance measures were excluded.

The authors conducted a literature search of databases including Medline ALL, EMBASE, PsycInfo, CINAHL, Web of Science, PubMed, International Clinical Trials Registry Platform, Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials from their inception until 26 July 2021. Authors also searched grey literature on Google Scholar, Open Grey, and ProQuest. There were no restrictions on language, publication date, or location. Reference lists of all included articles and previous reviews were also searched to identify other relevant studies.

Two reviewers independently screened identified studies for eligibility. Data was extracted separately from the included studies into a predesigned and piloted data spreadsheet. Two reviewers checked the data for errors, and discrepancies were resolved through discussion and consensus. Two reviewers independently evaluated the quality of each included study. Discrepancies were resolved through discussion and consensus. The studies were assessed for their methodological quality using the Joanna Briggs Institute Critical Appraisal Checklist tools.

The study characteristics were first described, followed by meta-analyses of reported outcomes. Outcome measurement tools were categorised into specific measures and domains. Hedges’ g effect size and 95% CI were used to characterise the association between uncorrected hyperopia and academic performance. The random-effects model was used to generate a pooled ES. Heterogeneity between study estimates was presented through forest plots and the I² statistic. All statistical analyses were performed using Stata. Sensitivity analysis was performed using the leave-one-out method. A narrative synthesis of the association between uncorrected hyperopia and educational outcomes was also performed.

Applicability/external validity: Authors indicate that quality of included studies was generally moderate to low, which may make their findings less applicable.

Geographic focus: Only two included studies were conducted in LMICs. Authors note that hyperopia is associated with disadvantage, and therefore a greater focus on data from low- and middle-income countries is needed.

Summary of quality assessment:

The methods for selecting, incorporating, and critically evaluating studies were solid, with at least two authors performing all essential tasks and a highly inclusive search without restrictions on language, date, or publication status. The data analysis approach was generally robust as well, but there was no effort to evaluate the effect of including studies of varying quality levels in the meta-analysis, a task that would have been difficult due to the limited number of studies included. The authors acknowledge that most of the evidence in this review was of low to moderate quality. Therefore, we would assign medium confidence to the review’s findings.