Methodological quality of the review: Low confidence
Author: Taban M, Behrens A, Newcomb RL, Nobe MY, Saedi G, Sweet PM, McDonnell PJ.
Region: Europe, United States, Canada, India, Africa, Australia, Turkey, Nepal, Pakistan, Japan, New Zealand. One study covered Israel, Malaysia, Russia, Saudi Arabia and Singapore.
Sector: Cataract surgery, endophthalmitis
Sub-sector: Clear corneal incisions
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Regression analysis
Qualitative synthesis methods: Not applicable
Cataract extraction has undergone remarkable technological progress, where small incision phacoemulsification became possible in the late 1980s. Self-healing clear corneal incision was introduced in 1992 and since then, clear corneal incisions have increased in popularity over limbal and tunnel incisions among surgeons, especially in the United States and Europe. Endophthalmitis is a rare intraocular infection which occurs most commonly as a complication of intraocular surgery and can cause severe visual impairment. The reported incidence of endophthalmitis varies by procedure and across studies. However, recent studies have associated the increasing incidence of endophthalmitis with the development of clear corneal incisions.
To determine the reported incidence of acute endophthalmitis following cataract extraction over time and to explore possible contributing factors, such as type of cataract incision.
The systematic review included 215 studies, all of which addressed post-cataract (primary or secondary cataract surgery with or without intraocular lens implantation) endophthalmitis occurrence. It is not clear the types of studies included in the review.
Studies included were conducted in a number of high-, and low- to middle-income countries (see geographical coverage).
From the 215 included studies, a total of 3,140,650 cataract extractions were pooled resulting in an overall rate of 0.128% of post-cataract endophthalmitis. A significant increase in endophthalmitis rate was identified since 2000 compared with previous decades: 0.256% in 2000-2003, 0.087% in the 1990s, 0.158% in the 1980s and 0.372% during the 1970s.
An upward trend in rates after 1992 was noted, suggesting that incision type influenced risk. Endophthalmitis following clear corneal cataract extraction during 1992 and 2003 was 0.189% compared with 0.074% (relative risk, 2.55 [95% confidence interval, 1.75 -3.71]) for scleral incision and 0.062% (relative risk, 3.06 [95% confidence interval, 2.48-3.76]) for limbal incision.
Overall, authors concluded that the incidence of endophthalmitis associated with cataract extraction had increased over the last decade (review conducted in 2005). This trend coincides with the development of sutureless clear corneal incisions. They also note that most reports to date (2005) looking at the rate of endophthalmitis are limited to small sample sizes or the individual experiences of groups of surgeons or institutions. As a result, future research should be more thoroughly studied in ‘large-scale prospective trials’.
Inclusion criteria of studies consisted of studies written in English; examined human cases; examined primary or secondary cataract surgery with or without intraocular lens (IOL) implantation; and addressed postcataract endophthalmitis occurrence.
Authors conducted literature search on two databases, PUBMED and Cochrane, from 1963 to 2003; manually searched reference lists of original reports and review articles; reviewed major ophthalmic textbooks, key publishing proceedings and scientific session electronic abstracts (2001-2003). Although authors reported the process of study identification and data abstraction, it is not clear if these were conducted by two reviewers.
Authors conducted a weighted regression analysis to portray how postoperative infection rates were changing from 1964 to 2003. This period was also divided into two sub-periods to analyse the impact of the development of clear corneal incision technique.
Due to the small sample sizes and differing methodological approaches of the included studies (including varying definitions of endophthalmitis, and complications around the miscoding of endophthalmitis), it was recognized that there are limits to the statistical validity of the findings and the general applicability of the research.
Although the review included studies from a range of countries (as described above) including low- and middle-income countries, it was not possible from the review to draw conclusions regarding the applicability of findings to different settings.
The literature search covered relevant databases and reference lists in included studies, but authors/experts were not contacted for additional studies and the search was restricted to published English-language studies. Therefore, we could not be confident that relevant studies were not omitted. Characteristics of included studies such as intervention details, participants and outcomes were not reported by the authors. Additionally, the authors did not provide information on how many reviewers screened articles for their eligibility for inclusion in the review as well information on data extraction. As such, it was not possible to determine the appropriateness of the meta-regression analysis, the quality and risk of bias assessment of heterogeneity of included studies. However, authors concluded that there is clear evidence to support the notion that post-surgical acute endophthalmitis following cataract extraction has been increasing in the past decade and that this trend is associated with the increase prevalence of self-sealing clear corneal incision technique. Therefore, low confidence in the conclusions about the effects was attributed to this study.