Efficacy and Acceptability of Orthokeratology for Slowing Myopic Progression in Children: A Systematic Review and Meta-Analysis

Methodological quality of the review: Medium confidence

Author: DaizongWen, Jinhai Huang, Hao Chen, Fangjun Bao, Giacomo Savini, Antonio Calossi, Haisi Chen, Xuexi Li, and QinmeiWang

Region: China, Japan, Caucasian countries

Sector: Myopia

Subsector: Myopia treatment

Equity focus: Asian and Caucasian

Study population: Children and adolescents

Type of programme: Hospital based

Review type: Other review

Quantitative synthesis method: Systematic review and meta-analysis

Qualitative synthesis method: Not applicable

Background: Myopia has emerged as a worldwide public health issue because of its dramatically increased prevalence during the past few decades, especially in East Asia, with 60 to 90 per cent of youngsters affected. Myopic progression in young children is primarily due to eye elongation; in other words, the elongation of the axial length (AL) must be slowed to control myopia. For decades, researchers and clinicians have proposed approaches to slow myopic progression. However, no ideal therapeutic pathway has been identified for effective myopic progression reduction or prevention when efficacy, safety, economic feasibility and clinical acceptability are fully considered. Orthokeratology (OK) was first introduced in the early 1960s and is based on gas-permeable contact lenses that temporarily reshape the cornea surface to reduce myopia progression. However, OK is not widely used due to safety concerns and outcome unpredictability, although positive results have been reported. It is therefore necessary to evaluate the efficacy and acceptability of OK for slowing myopic progression in children with a well-conducted, evidence-based analysis. Concerning the difference in ethnicities between Asian and Caucasian – for both efficacy and acceptability – the results did not substantially contradict the original findings between orthokeratology and control.

Objectives: To evaluate the efficacy and acceptability of orthokeratology for slowing myopic progression in children with a well-conducted, evidence-based analysis.

Main findings: Eight studies describing a total of 769 subjects with myopia ranging from 0 to -10.00D (382 assigned to the treatment group and 387 to the control group) were included in this meta-analysis. Two studies were randomised controlled trials (RCTs), and the remaining six were cohort trials. Six of the eight studies used common OK as treatment, while the remaining two used partial reduction orthokeratology (PRok) and toric orthokeratology (Tok), respectively. The good quality of the studies was confirmed according to the quality scoring described before: the two RCT studies scored 4 points on the Jadad scale and the six non-randomised cohort studies had 6–9 points on the NOS. The pooled weighted mean difference (WMD) of axial length change between orthokeratology and control at 2-year follow-up shows a statistically significant difference was found (WMD, -0.25 mm; 95% CI, -0.30 to -0.21). No significant heterogeneity was detected. Regarding acceptability, the pooled ORs of dropout rate between orthokeratology and control shows no significant difference. The analysis comparing the different types of study design shows no significant influence across studies. In the different types of treatment and control, although statistical analysis of each subgroup demonstrated the robustness of the original results for both efficacy and acceptability, the effect size of OK versus SC (WMD, -0.32 mm; 95% CI, -0.50 to -0.14), PRok versus SV (WMD, -0.32 mm; 95% CI, -0.52 to -0.12), and Tok versus SV (WMD, -0.33 mm; 95% CI, -0.49 to -0.18) in efficacy was slightly stronger than that of OK versus SV (WMD, -0.24 mm; 95% CI, -0.29 to -0.19).

Methodology: Inclusion criteria consisted of: i) articles reporting randomised controlled studies (RCTs) and cohort studies; ii) for study population, patients aged 6 to 15 years with any degree of myopia, no significant co-pathology, no history of ocular surgeries, or no systemic disease associated with impaired or abnormal wound healing; iii) as intervention, eyes treated by orthokeratology versus control. Axial length change and dropout rates during the two-year follow-up were assessed as the primary outcomes. The mean axial length change and myopia control rate (treatment slowed axial elongation compared to control) during the treatment were used to assess efficacy. The number of patients who terminated the study early for any reason during the treatment (dropout rate) determined the acceptability.

Studies describing the comparative outcomes of orthokeratology and controls were identified through a systematic literature search (up to 1 November, 2014) in Medline, Embase, and the Cochrane Library. Ongoing trials were retrieved by searching the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov. Language restrictions were not used. Reference lists of the included articles were searched to find additional information about relevant studies. The quality of the trials was assessed using the Jadad scale for randomised, controlled studies and the Newcastle-Ottawa Scale (NOS) for non-randomised cohort studies. In the meta-analysis, weighted mean difference (WMD), odds ratios (ORs), and ninety-five per cent confidence intervals (CIs) were calculated. A P value of less than 0.05 was considered statistically significant. The chi-square and ?² statistics were determined for assessment of heterogeneity between studies.

Applicability/external validity: Regarding the external validity, the authors reported some limitations which need to be considered when using the finding externally. First, the sample size of included studies was relatively small, and this may lead to deviation or failure to detect actual differences. Some considerable parameters, including age and the dioptric refractive error, which might influence myopic control by OK, were not analysed, due to the lack of data. Finally, studies were identified as having short years follow-up.

Geographic focus: this review focuses on Asian and Caucasian ethnicities groups.

Summary of quality assessment:

Overall, medium confidence was attributed to the conclusions about the effects of this study. Although authors used appropriate methods to analyse findings of included studies, searches of the literature were not comprehensive enough to ensure that all potentially relevant studies were identified. In addition, it is not clear if two authors independently screened studies for inclusion in the review, increasing potential publication bias within the study.