Endophthalmitis outbreaks following cataract surgery: causative organisms, etiologies, and visual acuity outcomes

Methodological quality of the review: Low confidence

Author: Pathengay A, Flynn HW Jr, Isom RF, Miller D.

Region: Turkey, Nepal, India, United States of America (USA), Germany, Switzerland, Spain, Czech Republic, France, Italy, Saudi Arabia, Canada, Thailand.

Sector: Age-related cataract

Sub-sector: Surgery, clinical outcome

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

Outbreaks of endophthalmitis after cataract surgery are rare but can lead to poor visual outcome after surgery. Identifying the causes and infection source can help prevention and prompt treatment leading to better visual outcomes.

Research objectives

To summarize the existing evidence on the aetiology, causative organisms, and visual outcomes after endophthalmitis outbreaks following cataract surgery

Main findings

27 studies were included (1985 – 2011): 12 from Europe, eight from Asia, seven from USA, one from Thailand and Canada. The outbreaks affected 264 patients. Authors reported the following results:

1. Source of the outbreaks: Intraoperative solutions ( 37%), Phaco machines (22.2%), Ventilation systems (1.1%), Sterilization (11.1%), miscellaneous ( 11.1%), and no source identified (18.5%)
2. Causative organisms: Most outbreaks were caused by bacteria (85.2%) and the remaining by fungus (14.8%). Most bacteria were Gram-negative (65.2%), of which 93.3% were Pseudomonas aeruginosa. 21.7% were caused by Gram-positive bacteria and 13.1% by mixed infection.
3. Visual outcomes: recorded in 229 of the 264 patients. 55.5% of them had a visual acuity of 20/400 or better; 25.8% of patients had between 20/400 and light perception and 14.8% of them had no light perception.

Based on the results, authors concluded that outbreaks of endophthalmitis following cataract surgery are often caused by gram-negative organisms and can be associated with poor visual outcomes. In this review, the most common source was irrigation solutions used perioperatively.

Methodology

Authors included published articles written in English on outbreaks (three or more cases) of endophthalmitis after cataract surgery (Phaco, ECCE, and MSICS).

Authors conducted a search of PUBMED and reviewed reference lists from the articles identified in search to identify relevant studies published between 1985 and 2011. A single investigator reviewed all the articles and extracted data directly into an electronic summary. Authors did not report on the quality assessment criteria used to appraise included studies. However, methods used to analyse the findings were clear.

Applicability/external validity

The review did not clearly discuss the generalizability of findings and does not illustrate methods to assess applicability.

Geographic focus

Authors did not restrict their searches to high-income countries; low- and middle-income countries were also included in the review including India, Nepal, Turkey and Thailand.

Quality assessment

The literature search of this review was based on one database only and the reference lists of included articles, restricted to published articles written in English only. Authors did not conduct a search on at least one source of grey literature and did not contact authors/experts for additional articles. Therefore, we cannot be confident that relevant literature was not omitted.  Study selection and data extraction was not appropriately, as this was conducted by a single reviewer only.

Additionally, there was no evidence of critical appraisal of the studies included; and specific factors are not explained or considered particularly in reference to how different surgical techniques relate to the outcomes. The surgical technique used is directly related to the source of contamination which is one of the outcomes measured. There was no evidence of addressing the fact that not all the outbreaks happened using the same technique. This was particularly important given that ‘Phaco machines’ are said to be the second most common source of contamination. This could be an underestimation. Authors did not take into consideration that nine of the studies did not use Phaco machines. A separate analysis by surgical technique would have been pertinent. Therefore, there was low confidence in the conclusions about the effects of this review.