The first two laser treatments covered in this section are used to prevent and treat angle closure glaucoma. The third treatment is used to treat open angle glaucoma. The final treatment covered is used to treat both forms of glaucoma at the final stage of the disease.

Peripheral Iridotomy

Remember the part of the eye that drains fluid, known as the angle? Some people have suspiciously narrow angles. While a narrow angle does not pose a problem from day to day, there is a 1-2% risk that that angle could close off completely without warning. If that happens, the pressure in the eye, or IOP, could spike up suddenly over a few hours and cause intense pain, decreased vision, and rapid damage of the optic nerve. This is called acute angle closure glaucoma.

To prevent this sudden and painful form of glaucoma, eye care professionals actively look out for patients with narrow angles and offer them a preventative treatment called Peripheral Iridotomy. In this laser procedure, a small opening is created in the far corner of the iris. This provides an alternate pathway for the fluid to flow into the angle. The opening is so small that it cannot be seen without a microscope.

A peripheral iridotomy can also be performed in a patient who is actively in an acute angle closure episode. However, because the patient is in extreme pain at the time, most doctors prefer to perform the procedure in advance and prevent an angle closure attack in the first place.

A peripheral iridotomy is a very quick outpatient office procedure which is performed with the patient seated in a chair. The pupil, which is the dark circle in the center of the iris, is constricted with a drop called pilocarpine that may cause a slight brow ache.  The eye is then numbed with anaesthetic drops. A lens is then placed over the eye and the laser is administered over a few seconds. The patient is awake all along, and goes home the same day with a prescription for healing drops which should be taken for a few days. Overall, there is very little discomfort associated with this procedure.

A peripheral iridotomy is a very safe procedure. Rarely, there can be a small amount of bleeding which usually stops on its own in a few minutes. Sometimes, the IOP can increase for a short period of time, or a small amount of inflammation can occur. These complications can be treated with drops over a few days. A small percentage of people may also notice a small afterimage which is not typically bothersome.

Laser Peripheral Iridoplasty

While a peripheral iridotomy would open up a narrow angle in most cases, some people’s angles remain narrow even after this procedure. These people can then be considered for laser peripheral iridoplasty. In this procedure, rather than creating an opening in the iris, a gentle but focused laser is used to subtly change the shape of the iris and open up the angle that way.

From the patient’s perspective, the only difference is that this procedure takes a few minutes longer than the peripheral iridotomy. The before and after care are very similar, as are the complications.

Laser trabeculoplasty

Laser trabeculoplasty is used to treat open angle glaucoma. In this procedure, a very focused beam of laser is applied to the drainage angle directly. This stimulates the cells in the drain to work more effectively to allow fluid to leave the eye.  There are two types of lasers used in trabeculoplasty: the argon laser trabeculoplasty (ALT) and the selective laser trabeculoplasty (SLT). The ALT was developed first, and it uses a small laser beam of higher energy, while the SLT was invented later and uses a larger beam of lower energy. ALT works about 75-80% of the time, and studies show that SLT is equal to or slightly better than ALT in its effectiveness in lowering IOP.

Again, the patient’s experience with SLT/ALT is very similar to peripheral iridoplasty, although from the doctor’s perspective, the technique and purpose of the treatment is very different. SLT/ALT treatment can be administered at one clinic visit or broken up into two or more sessions.

Compared to glaucoma drops, SLT/ALT takes a bit longer to start working, and the effects can wear off in months or years. SLT/ALT can be repeated a number of times during a patient’s lifetime.

SLT or ALT can be used alone or in addition to drops to decrease IOP. The decision to use SLT/ALT instead or in addition to drops is usually made jointly by the doctor and the patient. SLT/ALT is not suitable for all glaucoma patients.

There a few risks associated with SLT/ALT:

  • Inflammation in the eye, which can usually be treated with drops.
  • A brief period of clouding of the clear covering of the eye (cornea) which can cause short-lived decreased vision.
  • Pain.
  • In rare instances, the drain close off after SLT/ALT.


All the laser treatments discussed so far were aimed at increasing fluid drainage out of the eye. In contrast, cyclophotocoagulation uses laser energy to decrease how much fluid the eyeball produces in the first place.

This procedure is usually offered to patients for whom most other medical, laser, and even surgical treatments have been tried without enough success. As such, these patients tend to have more advanced glaucoma. They may be nearly blind, or even be in severe pain due to long term high IOP. So cyclophotocoagulation is often used to help patients hold on to what little vision they have, and/or to treat the pain that some people experience when they have very high eye pressure. That being said, as technology improves, this procedure is starting to be used in more and more patients with moderate glaucoma.

Cyclophotocoagulation can be performed in the office or in the operating room, depending on the patient’s needs, and the availability of equipment. This procedure tends to hurt more than the previously discussed laser procedures. Therefore, most patients need deeper amounts of freezing anaesthetic into the back of the eyeball with a small, sterile needle. The procedure can last anywhere from fifteen minutes to an hour depending on many factors. Most patients do not need sedation to undergo this procedure.

It is still an outpatient procedure, and most patients go home with a prescription for healing drops. Patients will continue to be followed by their ophthalmologists on a regular basis even after this procedure is completed. Sometimes, it can be repeated after months or years if the effects start to wear off.

The risks of the procedure include

  • Abnormally low pressure in the eye
  • Inflammation in the eye
  • Clouding of the clear covering of the eye (the cornea)
  • Shrinking of the eyeball itself – while this was a concern in previous decades when the technology was new, this is now a very rare complication.