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Fornix-based versus limbal-based conjunctival trabeculectomy flaps for glaucoma

Overview of attention for article published in Cochrane database of systematic reviews, November 2015
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  • In the top 25% of all research outputs scored by Altmetric
  • High Attention Score compared to outputs of the same age (87th percentile)
  • Average Attention Score compared to outputs of the same age and source

Mentioned by

1 policy source
7 tweeters
3 Facebook pages
1 Wikipedia page


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Fornix-based versus limbal-based conjunctival trabeculectomy flaps for glaucoma
Published in
Cochrane database of systematic reviews, November 2015
DOI 10.1002/14651858.cd009380.pub2
Pubmed ID

Christiane Al-Haddad, Marwan Abdulaal, Ahmad Al-Moujahed, Ann-Margret Ervin


Glaucoma is one of the leading largely preventable causes of blindness in the world. It usually is addressed first medically with topical intraocular pressure-lowering drops or by laser trabeculoplasty. In cases where such treatment fails, glaucoma-filtering surgery is considered, most commonly trabeculectomy surgery with variations in technique, for example, the type of conjunctival flap (fornix- or limbal-based). In a fornix-based flap, the surgical wound is performed at the corneal limbus; while in a limbal-based flap, the incision is further away. Many studies in the literature compare fornix- and limbal-based trabeculectomy with respect to outcomes and complications. To assess the comparative effectiveness of fornix- versus limbal-based conjunctival flaps in trabeculectomy for adult glaucoma, with a specific focus on intraocular pressure (IOP) control and complications (adverse effects). We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2015, Issue 9), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to October 2015), EMBASE (January 1980 to October 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to October 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 23 October 2015.We reviewed the bibliographic references of identified randomised controlled trials (RCTs) in order to find trials not identified by the electronic searches. We contacted researchers and practitioners active in the field of glaucoma to identify other published and unpublished trials. We included RCTs comparing the benefits and complications of fornix- versus limbal-based trabeculectomy for glaucoma, irrespective of glaucoma type, publication status, and language. We excluded studies on children less than 18 years of age, since wound healing is different in this age group and the rate of bleb scarring postoperatively is high. Two review authors independently extracted data and assessed trial quality. We contacted study authors for additional information.The primary outcome was the proportion of failed trabeculectomies at 24 months. Failure was defined as the need for repeat surgery or uncontrolled IOP (more than 22 mmHg), despite additional topical/systemic medications. Needling and 5-fluorouracil (5-FU) injections were allowed only during the first six months postoperatively; additional needling or 5-FU injections were considered as failure. Mean post-operative IOP at 12 and 24 months also was recorded. The review included six trials with a total of 361 participants. Two studies were conducted in America and one each in Germany, Greece, India, and Saudi Arabia. The participants of four trials had open-angle glaucoma; one study included participants with primary open-angle or primary closed-angle glaucoma, and one study did not specify the type of glaucoma. Three studies used a combined procedure (phacotrabeculectomy). Trabeculectomy with mitomycin C (MMC) was performed in four studies, and trabeculectomy with 5-fluorouracil (5-FU) was performed in only one study.None of the included trials reported trabeculectomy failure at 24 months. Only one trial reported the failure rate of trabeculectomy as a late complication. Failure was higher among participants randomised to the limbal-based surgery: 1/50 eyes failed trabeculectomy in the fornix group compared with 3/50 in the limbal group (risk ratio (RR) 0.33, 95% confidence interval (95% CI) 0.04 to 3.10); therefore we are very uncertain as to the relative effect of the two procedures on failure rate.Four studies including 252 participants provided measures of mean IOP at 12 months. In the fornix-based surgeries, mean IOP ranged from 12.5 to 15.5 mmHg and similar results were noted in limbal-based surgeries with mean IOP ranging from 11.7 to 15.1 mmHg without significant difference. Mean difference was 0.44 mmHg (95% CI -0.45 to 1.33) and 0.86 mmHg, (95% CI -0.52 to 2.24) at 12 and 24 months of follow-up, respectively. Neither of these pooled analyses showed a statistically significant difference in IOP between groups (moderate quality of evidence).One trial reported number of anti-glaucoma medications at 24 months of follow-up with no difference noted between surgical groups. However, three trials reported the mean number of anti-glaucoma medications at 12 months of follow-up without significant difference in the mean number of postoperative IOP-lowering medications between the two surgical techniques. Mean difference was 0.02, (95% CI -0.15 to 0.19) at 12 months of follow-up (high quality of evidence).Because of the small numbers of events and total participants, the risk of many reported adverse events were uncertain and those that were found to be statistically significant may have been due to chance.For risk of bias assessment: although all six trials were randomised selection bias was mostly unclear, with unclear random sequence generation in four of the six studies and unclear allocation concealment in five of the six studies. Attrition bias was encountered in only one trial which also suffered from reporting bias. All other trials had an unclear risk of reporting bias as there was no access to study protocols. All included trials were judged to have high risk of detection bias due to lack of masking of the outcomes. Trabeculectomy is quite a standard procedure and unlikely to induce bias due to surgeon 'performance', hence performance bias was not evaluated. The main result of this review was that there was uncertainty as to the difference between fornix- and limbal-based trabeculectomy surgeries due to the small number of events and confidence intervals that cross the null. This also applied to postoperative complications, but without any impact on long-term failure rate between the two surgical techniques.

Twitter Demographics

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Mendeley readers

The data shown below were compiled from readership statistics for 90 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
United Kingdom 1 1%
Unknown 89 99%

Demographic breakdown

Readers by professional status Count As %
Student > Master 21 23%
Student > Bachelor 16 18%
Researcher 12 13%
Student > Postgraduate 8 9%
Student > Doctoral Student 5 6%
Other 13 14%
Unknown 15 17%
Readers by discipline Count As %
Medicine and Dentistry 41 46%
Nursing and Health Professions 8 9%
Social Sciences 5 6%
Pharmacology, Toxicology and Pharmaceutical Science 4 4%
Biochemistry, Genetics and Molecular Biology 2 2%
Other 14 16%
Unknown 16 18%

Attention Score in Context

This research output has an Altmetric Attention Score of 11. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 31 January 2020.
All research outputs
of 15,542,315 outputs
Outputs from Cochrane database of systematic reviews
of 11,212 outputs
Outputs of similar age
of 366,109 outputs
Outputs of similar age from Cochrane database of systematic reviews
of 217 outputs
Altmetric has tracked 15,542,315 research outputs across all sources so far. Compared to these this one has done well and is in the 88th percentile: it's in the top 25% of all research outputs ever tracked by Altmetric.
So far Altmetric has tracked 11,212 research outputs from this source. They typically receive a lot more attention than average, with a mean Attention Score of 23.0. This one has gotten more attention than average, scoring higher than 60% of its peers.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 366,109 tracked outputs that were published within six weeks on either side of this one in any source. This one has done well, scoring higher than 87% of its contemporaries.
We're also able to compare this research output to 217 others from the same source and published within six weeks on either side of this one. This one is in the 43rd percentile – i.e., 43% of its contemporaries scored the same or lower than it.