Methodological quality of the review: Medium confidence

Author: Guan-Lu Liang, Jing Wu, Jun-Ting Shi, Jian Liu, Feng-Ying He, Wen Xu

Region: China, Egypt, Spain, Iran, USA

Sector: Myopia

Subsector: Myopia treatment

Equity focus: No

Study population: Children

Type of programme: Hospital based

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Refractive surgeries, including laser corneal refractive surgery, phakic intraocular lens (PIOL) implantation, and clear lens extraction (CLE), are among the approaches which have been developed to treat myopia and particularly high myopia. Although laser corneal refractive surgery is effective and safe, and in most cases has been the preferred option for refractive surgery for the past 20 years, physical limitations that are imposed by the thickness and curvature of cornea render it incapable of treating ametropic eyes in certain circumstances, especially those with high refractive errors. Although large clinical studies have demonstrated that the Visian ICL and Artisan/Verisyse PIOL have good efficacy, predictability, stability and short-term safety, and despite several clinical comparative studies reporting disparate outcomes between the two types of PIOLs, no systematic review has compared their refractive outcomes.

Objectives: The aim of this study was to compare the efficacy, predictability and safety of correcting myopia via implantation of two types of phakic intraocular lens (PIOLs): the implantable collamer lens (ICL) and iris-fixed PIOL.

Main findings: A total of seven references met the inclusion criteria and were included in the study. These studies comprised two RCTs, one prospective non-randomised comparative study, and four cohort studies, involving a total of 511 eyes, of which 190 (37.18%) underwent ICL implantation and 321 (62.82%) underwent iris-fixed PIOL implantation. Based on the Quality Assessment Score (QAS), five studies were rated good and two were rated fair. On the efficacy, there was no difference in postoperative UDVA (log MAR) between the ICL and iris-fixed PIOL groups (SMD=20.22; 95% CI, 20.58 to 0.13, P=.22; I²=61.9%). Omitting Lee’s study, similar results were obtained (SMD=20.05, 95% CI, 20.29 to 0.19; P=.71; I²= 0%). Six studies [30-34,36] assessed safety, based on the number of eyes that lost one or more lines of postoperative BSCVA. No significant difference was observed between groups (RR=1.20; 95% CI, 0.24 to 6.00; P=.82; I² =37.5%). The incidence of the complications was also assessed, based on the safety index of the two types of PIOLs. The incidence of all complications did not differ significantly between groups (RR=0.78; 95% CI, 0.29 to 2.12; P=.63; I²=86.4%). There was a greater incidence of severe complications in the ICL group versus the iris-fixed PIOL group (RR=2.80; 95% CI, 1.04 to 7.52; P=.04; I²=0.0%). The incidence of all reported complications was 20.0% (38 of 190) in the ICL group, compared with 26.2% (84 of 321) in the iris fixed PIOL group. The ARR was 0.062, which translated into an NNT of 16. However, the incidence of severe complications was 6.32% (12 of 190) in the ICL group, significantly higher than the 2.18% rate (7 of 321) in the iris-fixed PIOL group. The ARI and NNH values were 0.041 and 24, respectively. Results indicate that predictability in the ICL group was better than in the iris-fixed PIOL group (RR=1.35; 95% CI, 1.04 to 1.77; P=.03; I²= 76.9%).

Overall, authors note that there is no significant difference in efficacy between the two types of PIOLs or in safety, except that the ICL is associated with a greater incidence of severe complications, especially anterior subcapsular cataract, primarily in the Version 2 and Version 3 groups. However, ICL has better predictability.

Methodology: Inclusion criteria consisted of studies which: 1) compare ICLs (sulcus-fixed PIOLs) and iris-fixed PIOLs (Artisan/Verisyse or Artiflex/Veriflex PIOLs) with regard to correction of myopia; 2) follow-up for a minimum of three months; and 3) report at least one of the outcomes below. Literature search was conducted in the Cochrane Library, including all sub databases up to 21 September 2013; PubMed from 1950 to 21 September 2013; and Embase from 1980 to 20 September 2013, were searched electronically using the terms phakic intraocular lens OR posterior chamber phakic intraocular lens OR ICL OR implantable collamer lens OR implantable contact lens OR staar OR ciliary sulcus-fixed OR ciliary-fixed OR Artisan OR Verisyse OR Artiflex OR Veriflex OR irisfixed OR iris-fixated OR iris-claw, combined with myopia OR shortsightedness OR nearsightedness. The search was restricted to clinical studies and studies in Embase that were published in English. Information on the included studies, the name of the first author, the year of publication, the country in which the study was conducted, the number of eyes into which the PIOLs were implanted, the mean age of the patients who underwent PIOL implantation, the follow-up time, the preoperative spherical equivalent (SE) and uncorrected distance visual acuity (UDVA), and the refractive outcomes. Downs and Black quality method, which is appropriate for RCTs and non-RCTs, was used to assess the qualities of the studies. The chi-square and I² tests were used to assess the heterogeneity of the studies. In our study, the random-effects model, which calculates a more conservative value and is less influenced by the weight of each study, also weights the studies relatively more equally than a fixed-effect analysis in the presence of heterogeneity as per the Cochrane Collaboration Handbook, was used, regardless of heterogeneity. Publication bias was assessed by Egger regression asymmetry test and Begg adjusted rank correlation test.

Applicability/external validity: Regarding external validity, the authors highlighted limitations which must be considered when reading the results: the studies had a small sample size, insufficient follow-up duration, and several designs. The effects of age, degree of myopia, preoperative BSCVA and other factors were not analysed due to insufficient information.

Geographic focus: Only studies from six countries were included; there was no study from LMIC.

Summary of quality assessment:

Medium confidence was attributed to the conclusions about the effects of this study. Literature searches were not comprehensive enough to ensure that all potentially relevant studies were identified, and language bias was not avoided as studies written in English only were included in the review. The authors also acknowledged the low sample of this review which can affect the conclusion.