The use of additional medication during cataract surgery to improve the continued success of a pre-existing operation (trabeculectomy)

Why is this question important?
Glaucoma and cataract are a global problem that can impact a person's economic and social circumstances. Vision loss from glaucoma is permanent, as the increased eye pressure that occurs in glaucoma damages the optic nerve which carries signals from the eye to the brain. The primary aim of treatment for glaucoma is to reduce this pressure, hence slowing down any progressive damage to vision.

Although medical and laser treatments are effective in treating glaucoma, an operation known as a trabeculectomy is required when these treatments do not stop progression of damage to vision. A small hole is cut in the white of the eye to allow excess fluid to drain from the eye. When a person with a trabeculectomy undergoes cataract surgery, an additional medication is often used to stop the eye healing too much and creating scar tissue, which can block the drainage hole and cause the trabeculectomy to fail.

In this review, we looked at patients with a functioning trabeculectomy who were undergoing cataract surgery and who received additional medication (5-fluorouracil, mitomycin C, or anti-vascular endothelial growth factor therapy) versus those who did not receive any additional medication.

How did we identify and evaluate the evidence?
We searched for randomised controlled trials (studies in which people are randomly assigned to one of two or more treatment groups), because these studies provide the strongest evidence about the effects of a given treatment. We planned to combine the results of the included studies to arrive at an answer to our research question.

What did we find?
We found no randomised controlled trials that met our inclusion criteria.

What does this mean?
We do not know whether an additional medical treatment during cataract surgery improves the chances of the drainage hole remaining open, as there is no evidence at present. It would be helpful if more studies were conducted in this area in future.

How up-to-date is this review?
The evidence in this Cochrane Review is current to April 2021.

Authors' conclusions: 

There is a need for an RCT to investigate the role of adjuvant wound modulating therapy at the time of cataract surgery to promote survival of a functioning trabeculectomy.

Read the full abstract...

Trabeculectomy is a surgical treatment for glaucoma to lower intraocular pressure with high success rates; however, it is often associated with an increased rate of cataract formation. Cataract can cause symptoms such as glare in bright conditions, foggy vision, and difficulty in driving at night. Cataract extraction surgery is highly successful in improving vision, but it comes at a cost of trabeculectomy failure, with a reported risk of 30% to 40%. An additional intervention to promote trabeculectomy survival after cataract extraction is needed. This review encompassed all adjunctive therapies used at the time of cataract surgery to increase trabeculectomy survival rate.


To investigate the effect of the adjunctive modulation of wound healing during cataract surgery on the survival of a previously functioning trabeculectomy.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; which contains the Cochrane Eyes and Vision Trials Register; 2021, Issue 4); Ovid MEDLINE; Ovid Embase; the ISRCTN registry;; and the WHO ICTRP. We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 14 April 2021.

Selection criteria: 

We planned to include all randomised controlled trials (RCTs) of participants who had a functioning trabeculectomy and were undergoing cataract surgery that compared any adjunctive therapy intended to modulate wound healing (such as 5-fluorouracil, mitomycin C, or anti-vascular endothelial growth factor (VEGF) therapy) with no adjuvant therapy. 

Data collection and analysis: 

We used standard methods expected by Cochrane. Our primary outcome was trabeculectomy failure at 6 months and 12 months after cataract surgery. Secondary outcomes were mean intraocular pressure difference from pre-cataract surgery baseline to 6 to 18 months post-cataract surgery; number of medications required to control eye pressure compared to before cataract surgery; bleb appearance as measured by a summation score of the Moorfields bleb grading system or other equivalent numerical grading systems; visual field progression measured by difference in mean deviation from baseline; and any complications.

Main results: 

We did not identify any RCTs of adjunctive modulation of wound healing during cataract surgery to promote survival of a previous trabeculectomy.