iStent with phacoemulsification versus phacoemulsification alone for patients with glaucoma and cataract: a meta-analysis

Methodological quality of the review: Medium confidence

Authors: Malvankar-Mehta MS, Iordanous Y, Chen YN, Wang WW, Patel SS, Costella J, Hutnik CM

Region: Italy, Spain, USA, UK, Finland, Turkey, Israel, New Zealand and Germany

Sector: Treatment

Sub-sector: See above

Equity focus: Adults aged 18 years and older

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Minimally invasive glaucoma surgeries have attracted significant attention, as they have been reported to lower intra-ocular pressure (IOP) and have an excellent safety profile. The iStent is an example of a minimally invasive glaucoma device that has received particular attention due to its early and wide spread utilization. There is a growing body of evidence supporting its use at the time of phacoemulsification to help lower IOP. However, it is still not clear how much of the IOP lowering effect can be attributed to the iStent, the crystalline lens extraction, or both when inserted concurrently at the time of phacoemulsification. This has been an important issue in understanding its potential role in the glaucoma management paradigm.

Objectives:

Compare the IOP lowering effect of iStent insertion at the time of phacoemulsification versus phacoemulsification alone for patients with glaucoma and cataracts.

Main findings:

In total, the authors included 32 articles in their quantitative and qualitative synthesis. A total of 18 studies were conducted in USA, four in UK, three in Italy, one in each country including Turkey, Spain, Germany, Finland, New Zealand, Japan, and Israel. Of the 32 studies, 21 were case series, two were case control, four were randomized control trials, and five were cohort studies.

The authors note that a 4% IOP reduction (IOPR%) from baseline occurred following phacoemulsification as a solo procedure compared to 9% following an iStent implant with phacoemulsification, and 27%following 2 iStents implants with phacoemulsification. Compared with cataract extraction alone, iStent with phacoemulsification resulted in significant reduction in the post-operative IOP (IOPR%) (standard mean difference – SMD = -0.46, 95%CI: [-0.87, -0.06]). A weighted mean reduction in the number of glaucoma medications per patient was 1.01 following phacoemulsification alone compared to 1.33 after one iStent implant with phacoemulsification, and 1.1 after 2 iStent implants with phacoemulsification. Compared to cataract extraction alone, iStent with cataract extraction showed a significant decrease in the number of glaucoma medications (SMD = -0.65, 95% CI: [-1.18, -0.12]). The authors also stated that the funnel plots suggested the absence of publication bias.

The authors concluded that both iStent implantation with concurrent phacoemulsification and phacoemulsification alone result in a significant decrease in IOP and topical glaucoma medications. In terms of both reductions, iStent with phacoemulsification significantly outperforms phacoemulsification alone.

Methodology: 

The authors note that a minimum post-op period of two months was required for inclusion in order to limit the confounding effects of short-term fluctuations in IOP that can occur in the immediate post-operative period due factors such as retained viscoadaptive devices. Only studies published in the English language were included. Research studies such as journal articles, systematic reviews, meta-analysis, cost analysis, cost-utility analysis, cost-effectiveness analysis, multicenter studies, randomized controlled trials (RCTs), quasi-RCTs, non-randomized studies including cohort studies (retrospective, prospective), clinical trials, and comparatives studies, were included for analysis. A minimum sample size of 20 patients was required for inclusion. Additionally, the study population included adults above the age of 18 with OAG or ocular hypertension. Studies examining subjects with other types of glaucoma were excluded.

Computer databases including MEDLINE (OVID and Pubmed), EMBASE (OVID), BIOSIS Previews (Thomson-Reuters), CINAHL (EBSCO), Health Economic Evaluations Database (HEED), ISI Web of Science (Thomson-Reuters) and the Cochrane Library (Wiley) were searched from the year 2000 to June 2014. The reference lists of all the included articles were hand searched to find potentially relevant studies. Grey literature was identified by searching the conference abstracts of various meetings including the Canadian Ophthalmology Society meeting (COS), American Academy of Ophthalmology annual meeting (AAO), European Society of Ophthalmology (SOE) and others. The Proquest Dissertations and Theses databases and the Canadian Health Research Collection (Ebrary) were also searched for relevant content. Google and other internet search engines were used to search for additional web-based materials and information. OVID auto alerts were set up to send monthly updates with any new literature.

Two authors independently screened studies for inclusion in the review. Data extraction was conducted by one reviewer and verified by second reviewer.

The authors conducted a meta-analysis. The abstracted data and standard error of the IOP at baseline and end-time point were used to compute the mean IOP reduction within group standard error of percentage of IOP reduction.

Applicability/external validity:

The authors did not discuss the applicability or external validity of findings

Geographic focus

The authors did not discuss the applicability of findings specific to low- and middle-income countries.

Summary of quality assessment:

Overall, medium confidence was attributed to the conclusions about the effects of this study as limitations were identified. The authors did not conduct a thorough search of the literature to ensure that all relevant studies were included in the review. It is not clear the quality of evidence included in the review, which on the other hand may have an impact on the overall of findings of the review. Nevertheless, the authors appropriately addressed all relevant limitations of included studies and on the methods used to conduct the review.