Methodological quality of the review: Low confidence
Author: Vanner EA, Stewart MW.
Region: United States of America (USA), Canada, Europe, India, Hong Kong, Australia, Japan, China, Turkey and Malaysia.
Sector: Vitrectomy, retained lens fragments, cataract surgery, age-related cataracts.
Sub-sector: Vitrectomy timing
Type of cataract: Age-related cataract
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis methods: Not applicable
Intravitreal retained lens fragments is a potentially serious, if rare, complication of cataract surgery that can result in poor visual acuity and other complications. A pars plana vitrectomy (PPV) can be conducted by a surgeon to treat the complication, improve visual acuity and reduce any inflammation. Optimal timing of this treatment is currently unknown, with some surgeons favouring an early vitrectomy (within a week or two or on the same day as surgery) whilst others wait to perform a PPV only when the patient presents a need for the treatment such as increased intraocular pressure, being unresponsive to medication or experiencing a severe inflammatory response. The literature is mixed with some research favouring early vitrectomy and some which do not.
To evaluate the effect of vitrectomy timing on outcomes for patients with crystalline retained lens fragments receiving vitrectomy three or more days after cataract surgery.
Authors included 53 retrospective interventional case series articles that addressed retained lens fragments after surgery for age-related cataracts and included a discussion on vitrectomy timing (three or more days). The results are based on 22 of those articles being included in the systematic review only and 31 articles included in a meta-analysis; 28 studies were conducted in the USA and Canada, 16 in Europe, eight in Asia and one in Australia.
Early vitrectomies were statistically significantly associated with better outcomes for not good visual acuity (odds ratio: 1.13; 95% CI: 1.04–1.22, P =.005); bad visual acuity (odds ratio: 1.05; 95% CI: 1.01–1.09, P =.009); pre-vitrectomy retinal detachment (odds ratio: 1.29; 95% CI: 1.01–1.65, P =.038); post-vitrectomy retinal detachment (odds ratio: 1.13; 95% CI: 1.02–1.26, P =.024); increased intraocular pressure (odds ratio: 1.23;95% CI: 1.07–1.41, P =.003); and intraocular infection/ inflammation (odds ratio: 1.20; 95% CI: 1.01–1.42, P =.041).
Based on these findings, authors concluded that ‘reduced vitrectomy delays may yield better patient outcomes’. Authors suggested that more research needed to be conducted to further narrow down the precise optimal vitrectomy timing, since this review was limited in its ability to discern optimal times within the three- to seven-day time period from the literature reviewed. Authors also suggested a need to explore further the mixed results around same-day vitrectomy to determine when a same-day vitrectomy might be performed and investigate when medical management (as opposed to surgical management) of retained lens fragments might be considered.
All study designs were considered for inclusion that addressed retained lens fragments after surgery for age-related cataracts and included a discussion or reported on vitrectomy timing (three or more days). Outcomes measured included: visual acuity, retinal detachment, increased intraocular pressure, intraocular infection/inflammation, cystoid macular oedema, and corneal oedema.
The review was based on a search of MEDLINE and article reference lists. It was noted that only one database was searched and only articles written in English were included in the review. Authors of the included reviews were not contacted as part of the search strategy. The screening of articles or data extraction was not conducted by two reviewers independently. This meta-analysis was part of the research that the first author, EA Vanner, used for her PhD dissertation. Therefore, all screening of articles and data extraction was performed by EA Vanner, as is appropriate for dissertation-related research, albeit not preferred for meta-analyses. However, in an attempt to simulate screening of articles and data extraction by two authors, as noted in the article, data were extracted twice (by EA Vanner), about three months apart, and discrepancies were resolved by re-examination of the article.
Authors conducted meta-analysis using data from 31 of the included articles and conducted a subgroup analysis which assessed how results differed between studies that included patients with only nuclear fragments and studies that also included patients with cortical fragments. Study quality was assessed using a method proposed by Minckler (2000) in ‘evidence-based ophthalmology series’.
The authors did not discuss the applicability/external validity of the results.
The review did not specifically focus on low- to middle-income countries, with most studies originating from Europe, the USA and Canada. The applicability of the results to low- and middle-income countries was not made clear in the review.
A search of the literature was not sufficiently comprehensive, as only one database and references of articles were searched restricting to studies written in English. Therefore, we cannot be confidence that relevant studies were not omitted.
The methods used to analyse the findings were clear. However, authors recognized that many studies included did not report data for all eight outcome measures identified. Furthermore, all included studies were retrospective interventional studies which, as authors noted, a weaker level of evidence than is often used in meta-analysis and this should be taken into consideration.
Selection bias is the most serious bias concern in retrospective interventional studies. The authors noted that, in all studies, selection bias (alone) would have yielded better results for later vitrectomy because poorer visual acuity and more intense reaction to the retained lens fragments lead to earlier vitrectomy. The authors reported that ‘the widely acknowledged selection bias favouring later vitrectomy was consistent among studies. Overall, despite this selection bias, results indicated, for early vitrectomy: (1) Six statistically significantly better outcomes (good VA [visual acuity], bad VA, previtrectomy RD [retinal detachment], postvitrectomy RD, increased IOP [increased intra-ocular pressure], and intraocular inflammation/ infection); (2) effects that were generally robust; and (3) a clinically significant composite effect.’ Clearly, this could not obviate the issue of selection bias, but it did strengthen confidence in the results of the meta-analysis.
As also noted, results from the meta-analyses in this review should not be interpreted as if they were based on randomized controlled trials, which provide the preferred and highest level of evidence. However, no randomized controlled trials were found in the search. We believe that the review should be attributed low confidence because of the weak level of evidence (mostly small studies all of which were retrospective interventional studies) and the fact that all study screening and data extraction were performed by a single author.
Vanner EA, Stewart MW. Vitrectomy Timing for Retained Lens Fragments After Surgery for Age-Related Cataracts: A Systematic Review and Meta-Analysis. American Journal of Ophthalmology. 2011;152(3):345-57.