What are the benefits and risks of minimally invasive Schlemm's canal surgery for treating the common eye condition glaucoma?

Key messages

• When types of minimally invasive glaucoma surgery that act on Schlemm's canal (called SC-MIGS) are compared with non-minimally invasive (conventional) glaucoma surgeries, there may be little to no difference in the proportion of people who are medication-free in the short, medium, or long term.

• More people may be medication-free in the short term after SC-MIGS compared with cataract surgery alone; however, there may be a higher risk of bleeding.

• SC-MIGS may reduce eye pressure more than laser treatment.

What is open-angle glaucoma?

Open-angle glaucoma is a common eye condition in which there is damage to the optic nerve, which usually progresses slowly over many years. 'Open-angle' means that the eye's natural drainage channels are not blocked but do not drain fluid effectively. This can increase pressure in the eye and damage the optic nerve, causing vision loss, often affecting the peripheral vision before the central vision. Some people develop glaucoma despite normal eye pressure and require further pressure-lowering treatment.

How is open-angle glaucoma treated?

Treatment includes eye drops, laser treatment, and surgery. Surgery is usually used if eye drops or laser treatment has not worked.

Standard surgery usually involves bypassing the drainage channels of the eye to improve fluid drainage. It may be performed under local anaesthetic (while the patient is awake) or general anaesthetic (while the patient is asleep). Complications, such as bleeding in the eye or very low eye pressure, can occur, and some people may need repeat surgery.

One alternative to standard surgical procedures is minimally invasive glaucoma surgery. Some of these procedures act on a part of the drainage network of the eye called Schlemm's canal.

What did we want to find out?

We wanted to find out whether these types of minimally invasive glaucoma surgery that specifically act on Schlemm's canal (called SC-MIGS below) help improve outcomes and whether they cause any harmful or unwanted effects in people with open-angle glaucoma. We were particularly interested in:

• the likelihood of people not needing eye drops;

• the likelihood of progressive visual field loss (loss of central or side areas of vision);

• changes in eye pressure;

• changes in the number of eye drops used following surgery;

• any unwanted effects or side effects.

What did we do?

We searched for studies that compared SC-MIGS to other types or combinations of surgery, or to laser treatment. We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and sizes.

What did we find?

We found 10 studies that involved 639 people (639 eyes). People in the studies were men and women aged between 41 and 74 years. The studies took place in Italy, Japan, India, the USA and Latin America, Poland, Canada, and China. The studies compared:

• SC-MIGS with conventional glaucoma surgery;

• SC-MIGS plus cataract surgery with cataract surgery alone;

• SC-MIGS with types of minimally invasive glaucoma surgery that don’t act on Schlemm’s canal;

• one type of SC-MIGS with another type of SC-MIGS;

• SC-MIGS with laser procedures.

SC-MIGs versus standard glaucoma surgery (3 studies, 99 people)

There may be no difference between SC-MIGS and standard glaucoma surgery in the likelihood of people not needing eye drops to control their glaucoma, having progressive visual field loss, or in the average change in eye pressure, number of eye drops people used following surgery, or unwanted effects.

SC-MIGS plus cataract surgery versus cataract surgery alone (2 studies, 132 people)
People may be less likely to need eye drops to control their glaucoma, average change in eye pressure may be greater, but there may be more risk of bleeding with SC-MIGS plus cataract surgery compared with cataract surgery alone.

SC-MIGS versus types of minimally invasive glaucoma surgery that don’t act on Schlemm’s canal (2 studies, 238 people)
There may be no difference between these two treatments in how likely people are not to need eye drops to control their glaucoma, number of eye drops used following surgery, or need for further surgery.

One type of SC-MIGS versus another type of SC-MIGS (2 studies, 140 people)
There is likely no difference between one type of SC-MIGS and another in any of the things we wanted to find out.

SC-MIGS versus laser procedures (1 study, 30 people)
Eye pressure may be reduced more, but there may be more risk of bleeding with SC-MIGS compared with laser procedures.

What are the limitations of the evidence?

Our confidence in the evidence is very limited because there were not many studies, and they did not include many people. The studies did not use the best methods, so their results may not be reliable. Also, the studies each focused on a small group of people of the same ethnicity or nationality, so we don’t know how their findings will apply to different groups of people.

How up to date is this evidence?

The evidence is up to date as of October 2025.