Effect of Implanted Capsular Tension Ring on Postoperative Refractive Shift: A Systematic Review and Meta-Analysis

Author: Xu S, Zhang Y, Li X, Si W, Tian G, Yang Y, Hu Y, Zhang F.

Geographical coverage: Not reported

Sector: Post-operative refraction

Sub-sector: Prediction error

Equity focus: Not reported

Study population: Patients with cataract

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Cataract remains a leading cause of visual impairment despite advances in surgical techniques. Zonular dialysis (ZD) — often a result of trauma, Marfan syndrome or high myopia — leads to weakened zonules and thus complicates cataract surgery. Capsular tension rings (CTRs) are designed to stabilise the capsule and maintain intraocular lens (IOL) position by distributing zonular tension. Their use has been shown to improve outcomes in patients with ZD by enhancing capsular stability and minimising complications. However, there is ongoing debate about the refractive effects of co-implanting CTRs with IOLs during cataract surgery. Specifically, it remains unclear whether CTR co-implantation leads to a myopic or hyperopic postoperative refractive shift. Only a limited number of clinical trials have examined this issue, and their findings highlight the need for further evaluation of the impact of CTR use on refractive outcomes.

Objective: To determine the postoperative refractive prediction error and the direction of refractive shift in cataract patients undergoing capsular tension ring co-implantation.

Main findings: The review included eight studies with a total of 407 eyes (206 in the CTR group and 201 in the control group). Two of these studies were prospective and six were retrospective. The CTR group had a significantly different arithmetic refractive prediction error (ArRPE) compared to the control group at both short-term and long-term follow-up. At short-term follow-up, the weighted mean difference (WMD) in ArRPE was 0.16 (95% confidence interval [CI] 0.13 to 0.19; p < 0.001), and at long-term follow-up it was 0.19 (95% CI 0.15 to 0.23; p < 0.001). However, in patients with high myopia, no significant difference in ArRPE was observed between those with and without a CTR (WMD 0.03, 95% CI –0.27 to 0.34; p = 0.083).

Regarding absolute refractive prediction error (AbRPE), no statistically significant difference was found between the CTR and control groups, regardless of high myopia status or follow-up duration. Furthermore, the two groups did not significantly differ in the number of eyes falling within any given refractive prediction error range.

Methodology: PubMed, Embase, the Cochrane Library, Web of Science, and China National Knowledge Infrastructure (CNKI) were searched for studies involving adult patients undergoing cataract surgery with or without CTR implantation. Studies published up to March 2024 that reported at least one of the following outcomes were included: ArRPE, AbRPE, or the number of eyes within a specified refractive prediction error range. The reference lists of relevant reviews were also scanned to identify any additional studies.

Two reviewers independently screened all identified studies, extracted relevant data, and assessed study quality. Any disagreements were resolved through discussion. The methodological quality of the included studies was evaluated using the Cochrane Collaboration’s Risk of Bias tool for prospective studies and the Newcastle–Ottawa Scale for retrospective studies. Meta-analyses were performed using fixed- or random-effects models as appropriate based on the level of heterogeneity. Heterogeneity was assessed using a chi-square test and the I² statistic. A sensitivity analysis was conducted to examine the influence of each individual study on the pooled estimates. A subgroup analysis was performed for patients with high myopia (defined by axial length), and refractive prediction error data were stratified into three subgroups based on error magnitude (0.5 D, 1.0 D, and 2.0 D).

Applicability/external validity: The review highlighted the small number of included studies, the lack of data in certain subpopulations (such as those with high myopia), and variability in follow-up durations. It emphasised the need for further large-scale, high-quality studies to confirm and broaden these results.

Geographic focus: No geographical limits were applied in the search; however, the review did not report the geographical distribution of the included studies.

Summary of quality assessment: Overall, there is medium confidence in the review’s conclusions. The literature search was comprehensive, with clearly defined inclusion and exclusion criteria. Study quality was assessed, and the results of these assessments were reported. Two reviewers independently screened the articles and extracted data. Characteristics of the included studies were presented. The data were synthesised using meta-analysis, and heterogeneity was assessed using a chi-square test and the I² statistic. Subgroup and sensitivity analyses were also conducted. However, the review did not provide a list of excluded studies, and it was unclear whether any language restrictions were applied to the search.