Methodological quality of the review: Low confidence
Author: Vanner EA, Stewart MW.
Region: United States of America/Canada, Europe, Asia and Australia.
Sub-sector: Retained lens fragments, time factors, visual acuity
Type of cataract: Age-related cataract
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis methods: Not applicable
The timing of pars plana vitrectomy (PPV) to remove retained lens fragments is controversial, especially concerning whether, and under what circumstances, a ‘same day’ (SD) (as the cataract surgery) vitrectomy (SD-PPV) might be performed. Policies for performing SD-PPV differ among facilities. Lack of the necessary equipment and/or the immediate availability of an experienced vitreoretinal surgeon may preclude an SD-PPV. Several authors reported better visual acuity (VA) and lower rates of complications (including retinal detachment, increased IOP, corneal oedema, CME, and intraocular inflammation/infection) among patients who had SD-PPV compared with delayed vitrectomy (DEL-PPV), but these differences were not always statistically significant. Other authors reported little or no differences in these and other outcomes when comparing SD-PPV and DEL-PPV.
To perform a systematic review and meta-analysis comparing the risk difference of clinical outcomes for same-day (SD) vs delayed (DEL) pars plana vitrectomy (PPV).
Of the 304 articles identified, 23 provided data for the meta-analysis. However, of the 23 articles, 21 unique study cohorts had the data necessary for the SD-PPV vs DEL-PPV meta-analysis. In 18 of the 23 articles, patients were consecutive series (a representative sample of the population), but only one article was a prospective study.
Six articles were conducted in the USA/Canada, nine were from Europe, five were from Asia, and one was from Australia.
Results were mixed, indicating:
1) Neither vitrectomy time produced better outcomes in all studies (not good VA risk difference =10.3% [positive numbers favoured SD-PPV; negative numbers favoured DEL-PPV], 95% confidence interval [CI] = [-0.4% to 21.0%], P=0.059; and bad VA risk difference =-0.3%, 95% CI = [-10.7% to 10.1%], P=0.953);
2) Better outcomes with immediate SD-PPV compared with all DEL-PPV (not good VA risk difference =16.2%, 95% CI = [0.8% to 31.5%], P=0.039; and bad VA risk difference =8.5%; 95% CI = [0.8% to 16.2%], P=0.030);
3) Immediate SD-PPV and prompt DEL-PPV (three to 14 days after cataract surgery) had no significant differences and so may produce similar outcomes (not good VA risk differences range = [-19.9% to 6.5%], 95% CI = [-59.9% to 36.4%]; and bad VA risk differences range = [-6.9% to 7.4%], 95% CI = [-33.1% to 31.8%]).
Authors concluded that SD-PPV should be limited to facilities at which a vitreoretinal surgeon is immediately available. Otherwise, results of this study support referring a patient with retained lens fragments promptly to a vitreoretinal surgeon but did not support inter-facility transport for SD-PPV.
Authors noted that a multicentre randomized controlled trial would be needed to test a non-inferiority hypothesis comparing immediate SD-PPV and prompt DEL-PPV outcomes. Further research should analyse how SD-PPV results differ based on various SD-PPV strategies, to determine the optimal circumstances for an SD-PPV.
The primary outcomes for this meta-analysis were not good VA (<20/40) and bad VA (≤ 20/200). Secondary outcomes included retinal detachment, increased IOP, intraocular inflammation/infection, CME, and corneal oedema.
A study was included in the meta-analysis if it contained at least 10 patients who received a vitrectomy for intravitreal retained lens fragments after surgery for an age-related cataract; had a mean follow-up of at least 3 months; and had results for both SD-PPV and DEL-PPV patients, including the number receiving each treatment (SD-PPV and DEL-PPV), and the number in each treatment group who experienced at least one of the outcomes mentioned above. All study designs were considered.
Details of the search strategy used were reported in a companion article. The search was conducted on MEDLINE between 1985 and 2013, and as clarified and confirmed by the authors this was not conducted by two reviewers independently. Data extraction was performed twice by the same author, approximately three months apart and discrepancies were resolved by re-examination of the article. In order to determine the quality of each included study, authors used Minckler evidence-based rating system. Overall, the strength of evidence of all included studies was weak, mainly because the research was retrospective.
Authors conducted a meta-analysis using random-effects model. The summary effect for the meta-analysis was the risk difference of patients experiencing each outcome between the SD-PPV and DEL-PPV treatment groups. The risk difference for each study was the proportion of DEL-PPV patients minus the proportion of SD-PPV patients, so positive numbers ‘favoured’ (indicated superior outcomes with) SD-PPV, while negative numbers favoured DEL-PPV. Additional meta-analyses were conducted in order to determine variance between studies. Authors also assessed effects of reporting and publication biases; and assessed whether the results were robust with the sensitivity analysis. Results were statistically significant with P-value ≤0.05 and marginally significant with 0.05< P ≤ 0.15.
Authors did not discuss the applicability/external validity of the results.
This review included studies from USA/Canada, Asia, Europe and Australia. Authors did not discuss the applicability of the results in low- and middle-income countries.
This review was based on a search of one relevant database, and on references lists included, therefore, is not sufficiently comprehensive that we can be confident that relevant literature was not omitted. In attempt to simulate screening of articles and data extraction by two authors, as noted in the companion article, data were extracted twice (by EA Vanner) approximately three months apart, and discrepancies were resolved by re-examination of the article.
Authors concluded that results from the meta-analyses provide some preliminary evidence that SD-PPV may be unnecessary as long as prompt delayed vitrectomy (DEL-PPV, three to seven or perhaps even as long as three to 14 days after cataract surgery) would be performed. Nevertheless, it should be noted that included studies were mainly retrospective of weaker strength of evidence which may affect the overall validity of the results. Authors acknowledged some major limitations of the review, including the low power due to few patients with adverse events, especially in the SD-PPV group, which was generally much smaller than the DEL-PPV group; and potential selection bias as it was not possible to determine whether there were significant between-group differences in baseline variables. Selection bias was the most serious bias concern in retrospective studies. Although there was little evidence of publication bias, this should not be excluded completely as the search was restricted to studies written in English. Authors noted that studies included did exhibit reporting bias as authors are more likely to report significant rather than non-significant results; however reviewers stated that according to the sensitivity analyses reporting bias did not affect the overall conclusions of this study.
This review was attributed low confidence to the conclusions about the effects of the study due to the weak level of evidence included in the meta-analyses and the fact that all study screening and data extraction was conducted by a single author.
Vanner EA, Stewart MW. Meta-analysis comparing same-day versus delayed vitrectomy clinical outcomes for intravitreal retained lens fragments after age-related cataract surgery. Clin Ophthalmol. 2014;8:2261–76. Published online Nov 18, 2014.