Comparison of rigid versus foldable iris-fixed phakic intraocular lens implantation for high myopia: A systematic review and meta-analysis

Methodological quality of the review: Medium confidence

Author: Qiong Wu, Yan Li, Li Tang, Li-An Wu, Cong-Yi Wang

Region: Not reported

Sector: Myopia

Subsector: Myopia treatment

Equity focus: No

Study population: Adults

Type of programme: Community based

Review type: Other review

Quantitative synthesis method: Systematic review and meta-analysis

Qualitative synthesis method: Not applicable

Background: High myopia is usually defined as ametropia (refractive error) with >6.00 diopters. In 2018, 112 million people were affected by high myopia, accounting for the second most common cause of blindness globally. High myopia is complicated with a variety of fundus lesions, such as choroidal and retinal pigment epithelial atrophy, retinal detachment, retinal splitting, macular hemorrhage, macular and other complications. However, there is still a lack of effective treatment for high myopia. The use of frame glasses is a convenient and safe method to correct high myopia but some of them present great inconvenience to the life and vision of patients with high myopia. Refractive surgeries, such as laser corneal refractive surgery, phakic intraocular lens (PIOL) implantation, and clear lens extraction (CLE) have been developed for the treatment of high myopia. Since the role of rigid PIOL and foldable PIOL in the treatment of high myopia is still less evaluated, a number of studies with larger sample size and most up-to-date trials were conducted to obtain a more extensive and clearer evidence. However, no conclusive agreement was acquired due to the following limitations: insufficient number of comparative studies and lack of conformity in the duration of follow-up among observational studies due to bias.

Objectives: To clarify the efficacy and complications of rigid PIOL versus foldable PIOL implantation in the treatment of high myopia based on the evidence from previous comparative studies.

Main findings: A total of eight studies that met the eligibility criteria were included in this meta-analysis. Overall, the sample sizes ranged from 31 to 410. Eight studies were retrospective, one was a randomised controlled trial and one was a prospective study.

The total number of patients with high myopia was 835 (401 participants received rigid PIOL, and 434 participants received foldable PIOL). On the efficacity of UDVA, results show the forest plot for the proportion of eyes with postoperative UDVA of 20/20 or better. The pooled OR of postoperative UDVA of 20/20 was not significantly different between the rigid and foldable PIOL groups. The proportion of eyes with postoperative UDVA of 20/40 or better was higher in the foldable PIOL than in the rigid PIOL group (pooled OR=0.40, 95% CI=0.21-0.79, P=.55. Random effects analysis had to be used due to a significant heterogeneity among four studies (Q=I² 12.98, 77.00%, P<.01). The overall WMD was statistically significant (pooled WMD=0.10, 95% CI=0.04-0.11, Fig. 2C), revealing that foldable PIOL was superior to rigid PIOL in terms of postoperative UDVA. The proportion of eyes with postoperative SE within ±1.00D was better with foldable than with rigid PIOL (pooled OR=0.39, 95% CI=0.20-0.76. A significant difference was found in the mean postoperative CS at 3cpd (pooled WMD=-0.10, 95% CI=-0.23 to 0.02, P=.48, 6cpd (pooled WMD=-0.23, 95% CI=-0.35 to -0.11, P=.32, 12cpd (pooled WMD=-0.17, 95% CI=-0.28 to -0.06, P=.70), and 18cpd (pooled WMD=-0.21, 95% CI=-0.32 to -0.10, P=.75). The results suggested that there was no significant difference in the proportion of eyes that lost two or more lines of BSCVA in the rigid PIOL group. The direction of the combined estimates presented above showed no significant variations with the removal of the studies, indicating that the meta-analysis was robust, and the data was not overly influenced by any specific study. The results of the Egger and Begg tests showed no evidence of publication bias.

Based on findings of the meta-analysis, authors found that the foldable PIOL group had a significant beneficial effect on UDVA, SE, HOA, contrast sensitivity, and ECD, except best spectacle-corrected visual acuity, and safety in the treatment of high myopia over rigid PIOL group.

Methodology:

The inclusion criteria were as follows: 1) study design: comparative study; 2) population: patients with high myopia; 3) intervention: rigid versus foldable iris-fixated PIOL; and 4) follow-up: more than six months.

A systematic search was performed to identify relevant studies using electronic databases, such as PubMed, Embase, and the Cochrane Library published until 11 January 2019. The following key words were used for retrieving the articles: ciliary sulcus-fixed OR ciliary-fixed OR staar OR Artisan OR Verisyse OR Artiflex OR Veriflex OR irisfixed OR iris-fixated OR iris-claw) AND (myopia OR shortsightedness OR nearsightedness). In addition, authors manually searched the references of the original articles to retrieve any eligible articles for this meta-analysis. Studies were identified by two independent reviewers to determine their eligibility for inclusion. The following information on study characteristics and outcomes were extracted: name of the first author, year of publication, country, study design, number of participants, intervention type, age and major outcomes. The methodological quality of included studies was rated by using a modified version of the Downs and Black checklist.

For the meta-analysis, the odds ratio (OR) with 95% confidence intervals (CIs) was used to evaluate the binary data. The weighted mean differences (WMDs) with 95% CIs were used to evaluate the continuous data for each individual study. A x2-based test of homogeneity was performed using Cochran Q statistic and I². Random effects models of analysis were used if heterogeneity was detected (I2> 50%); and otherwise, a fixed effects model was used. A two-sided P value of <.05 was considered as statistical significance for one comparison group over the other. All analyses were performed using Net Meta XL (version 5.1).

Applicability/external validity: the authors reported that this review has a strength due to the inclusion of relatively homogenous studies owing to comparative study designs, ability to conduct a meta-analysis on multiple follow-up durations and focus on clinically relevant outcome measures. They have also reported some limitations which need to be taken into account when using the results externally: the protocol of PIOL implantation in the included studies was different, and the duration of intervention varied in the meta-analysis, which might confound the pooled results. The iris claws might be misplaced more often than others, the position of the lens should also be paid close attention to in the treatment of high myopia by rigid or foldable PIOL implantation.

Geographic focus: Not reported.

Summary of quality assessment:

Overall, there is medium confidence in the conclusions about the effects of this study. Although authors used appropriate methods to pool data for analysis, methods to search for literature were not thorough to ensure that all relevant studies were identified and included in the review, which can impact on the validity of findings.