Different Surgical Procedures

There are several different types of surgery. Each are explained in turn.

Laser Iridotomy

This is used when extensive posterior synechiae cause a pupillary block. Synechiae form when the iris is inflamed and they cause the pupil to become stuck in places. When the pupil is stuck, it may cause the iris to interfere with the drainage of the aqueous out of the eye because it closes the opening to the drainage channel.

You might have been told that you have ‘narrow angles’ or that you are in danger of developing ‘closed angle glaucoma.’ This link takes you to clear information, which includes an animation. Closed angle glaucoma is painful and the sudden onset of this is a medical emergency.

Good Hope Eye Department provide more detail and diagrams on angle closure glaucoma.

Surgical Iredectomy

Sometimes the drainage holes created in laser iridotomy close and a surgical iredectomy is performed. Instead of using a laser, an incision is made in the cornea just below the iris. This procedure is not as straightforward for the patient, is performed in an operating theatre and it may take a number of weeks before vision returns to the pre surgical level.


This is a surgical incision into the trabecular meshwork, which creates new channels for a better outflow of the aqueous.  Part of the trabecular meshwork is removed and a type of valve created.

A bleb (a bubble/blister) forms and this has to be prevented from healing in order for the trabeculectomy to work. The use of antimetabolites such as mitomycin C (MMC) or 5-fluorouracil (5-FU), help to ensure this happens.  Improved rates of success in uveitic eyes have been reported, when these agents are used.

There are more details available, including easy to follow trabeculectomy diagrams and animation.


This is similar to a trabeculectomy, except that incisions are made without removal of tissue.


This involves opening the Schlemm’s canal (which drains the aqueous) by an incision into the trabecular meshwork. Traditionally, it is a procedure that has been used in infants and very small children. It has a good rate of success in childhood JIA type uveitis and is sometimes considered for use in adult patients.

See the following for:

Shunts and Implants

These may be considered when there is a high risk that the trab procedures may fail through difficult to control uveitis, or a trab has already failed. Sometimes they are the first choice of procedure in particular types of uveitis.

They are small, plastic devices which are inserted into the eye and which allow the aqueous humor to exit the eye directly through them. Some have valves, such as the Ahmed implant, which have a cut off switch to stop flow when the intraocular pressure drops too low. Others, such as the Baerveldt and the Molteno, do not.

Complications of both types of device are that they may create a pressure that is too low or their position in the eye cause problems as time goes on.

A download from Moorfields Eye Hospital (PDF, 348 KB) provides information about aqueous shunt implantation.

Also see an overview of glaucoma procedures with information about newer shunts and the future of glaucoma therapy.

Further reading

If you wish to view actual operations, YouTube has plenty to choose from and videos are found on the UCL Institute of Ophthalmology site.