Under-correction or full correction of myopia? A meta-analysis

Methodological quality of the review: Low confidence

Author: Negareh Yazdania,b, Ramin Sadeghic, Asieh Ehsaei, Ali Taghipourd,Samira Hasanzadeh, Leili Zarifmahmoudi, Javad Heravian Shandiz

Region:

Sector: Myopia

Subsector: Under-correction or full correction

Equity focus: No

Study population: 6 to 33 years

Type of programme:

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Myopia has already become the most prevalent refractive error worldwide, and its incidence is increasing, particularly in young adults and school-aged children. For decades, researchers had typically focused on the genetic basis of the myopia. Under-correction is one of the interventions to reduce or slow myopia progression. One hypothesis about under-correction is that it may decrease the accommodative effort and also the lag of accommodation, and subsequently slow or reduce the myopia progression. Some studies have already compared under-correction versus full correction in myopic population. However, there is contradiction in the study’s findings with regards to the under-correction or full correction of myopia – it seems valuable to have a definite conclusion and provide, clinically, an appropriate and effective method of correction.

Objectives: The objective of this review was to investigate whether the under-correction is the method of choice for myopic patients or full correction is the better way.

Main findings: Overall, six studies were included in this meta-analysis. Two studies with randomized controlled trial (RCT) design; two studies with cross-sectional and two cohort studies. Two studies used cycloplegic auto refraction (group 1), and four studies used non-cycloplegic refraction with retinoscopy and auto refractometer, which were followed by refined subjective refraction based on maximum plus sphere as the end point for best corrected distance visual acuity (group 2). The pooled difference in mean of myopia progression using cycloplegic refraction was -0.179 D [lower and higher limits: -0.383, 0.025], which was higher in the full -correction group as compared to the under-correction group (P=0.085). In group 2, the pooled difference in myopia progression was 0.128 D [lower and higher limits: -0.057,0.312] higher in under-correction group compared with full-correction group (P=0.175). The Cochrane Q value was 6.99 (P=0.008) and I²=85.69 for cycloplegic studies, and Q value was 1.48 (P=0.686) and I²=0.000 for non-cycloplegic studies. The subgroup analysis of the results of the studies in group 1 and 2 demonstrated pooled progression rates of -0.26 diopter (95% CI -0.24 to -0.29) in group 1, in comparison with 0.15 diopter (95% CI 0.10 to 0.21) in group 2. Although, difference in means of progression was statistically significant in both types of refraction, the difference was not clinically significant.

Methodology: Studies concerning the difference between under-correction and full correction of myopia were considered for inclusion. Two researchers independently reviewed the titles and abstracts of the retrieved articles. Complete literature searches of the PubMed, ScienceDirect, Ovid, Web of Science, Scopus and the Cochrane Library databases were done to find relevant published articles on comparing under-correction with full correction of myopia. We used a search algorithm that was based on a combination of the terms: Under-correction, Full-correction, Myopia and Nearsightedness. The Boolean operators ‘‘AND’’ and ‘‘OR’’ were used in order to specify the search. No beginning date limit or language restriction was used; the search was updated until July 2019. To expand our search, references of the retrieved articles were also screened by two independent authors (NY and SH) for more related studies. Critical Appraisal Skills Program (CASP), was used to assess the methodological quality of included studies based on study design. For each study, the mean difference in myopia progression recorded in diopter notation was determined for the full-correction and under-correction groups. To pool the effect sizes across studies, a random effects model was used. The random effects model is a statistical method in which between study variability is accounted for. Heterogeneity was evaluated by the Cochrane Q test (the significance level was considered to be 0.05.) and I²

Applicability/external validity: The authors highlighted some limitations to be considered when interpreting the findings. These results showed the high heterogeneity added to this, there was also publication bias.

Geographic focus: Not discussed.

Summary of quality assessment:

There is low confidence in the conclusions about the effects of this study. Authors did not conduct thorough searches of the literature to ensure that all relevant studies were identified and included in the review. In addition, the search period was not comprehensive enough that relevant literature is unlikely to be omitted.