Selective Laser Trabeculoplasty (SLT)

Glaucoma is broadly of two types, open angle glaucoma in which the drainage angle is open and closed angle glaucoma with a narrow or closed drainage angles.

There are various types of lasers done for patients diagnosed with glaucoma or suspected to have early glaucoma. One of the commonest lasers is selective laser trabeculoplasty (SLT) which is done for open angle glaucoma or raised eye pressure without glaucoma or in angle closure patients in whom the angles have been opened either by laser or surgery.

SLT is one of the types of laser done for open angle glaucoma or raised intraocular pressure. This is a safe, effective and non-invasive procedure. This is done as an outpatient procedure and is not an operation.

This laser helps to improve the outflow of the fluid through the drainage network of the trabecular meshwork. The trabecular meshwork is a series of drainage channels in the periphery of the iris (the coloured area of the eye, surrounding the pupil). Specific areas of the trabecular meshwork are targeted by the laser to improve the outflow of the fluid from the eye and subsequently to reduce eye pressure. The laser doesn’t cause any permanent damage to the eye. The laser doesn’t reduce the pressure immediately. It takes nearly 4-6 weeks to take effect and some patients can have a late response as well.

SLT is one method to reduce eye pressure in addition to drops and surgery. It can be used as the only treatment or in conjunction with other drops depending upon individual circumstances, responses and stage of glaucoma. Mr Agarwal will discuss your personal circumstances with you and advise if SLT is an appropriate option for your eyes.

The aim of the laser is to reduce the intraocular pressure and decrease the risk of further damage to the optic nerve.

1. Some patients may not need to use the drops at all and are able to avoid all side effects related to drops.

2. Reduce the number of drops needed to use to control the intraocular pressure.

3. Avoidance of glaucoma surgeries for some patients. Therefore the associated risks of these procedures are avoided.

Some of the common reasons and indications why Mr Agarwal may suggest the laser include:

1. Poor control of glaucoma or worsening visual fields, despite maximal tolerated eye drop therapy

2. Poor adherence to medication

3. Ocular surface disease. This may be caused by side effects from eye drops or an unhealthy eye surface.

4. Reduced ability or difficulty instilling drops because of arthritis, poor memory or systemic side effects.

5. As a primary therapy for reducing intraocular pressure.

It is advisable to bring someone with you on the day of the laser and not to come to the clinic driving as the laser can transiently make your eyesight blurry. On the day of the appointment for the laser, some final checks will be done. The team will discuss with you about the laser again and you will get opportunity to ask any questions you might have before signing the consent form and agreeing to the procedure.

Eye drops will then be instilled in your eyes to help reduce the intraocular pressure to avoid any spikes in the pressure, as some patients can get a transient spike in the eye pressure after the laser. Local anaesthetic drops will also be instilled.

The laser is delivered by a machine similar to the one used to examine your eyes in the clinic. Once you are comfortably positioned, a small lens will be used to fix one eye at a time and to deliver the laser in the targeted way to the trabecular meshwork.

The procedure can be a bit uncomfortable mainly because of the lens touching your eyes, and you may feel this against your eyelashes, it is usually not painful. You will see some bright lights during the laser. The laser itself takes 3-5 minutes for each eye. The laser can be done in one eye at a time or both eyes at the same sitting.

After the procedure, the doctor might request you to wait for 30 minutes to one hour to check the eye pressure before you go home. This is to make sure you do not experience any spikes in the pressure.

There are no restrictions in any of your day to day activities after the laser.

If you already on drops for glaucoma or other eye conditions, do not stop them before or after the laser unless advised by the doctor. You need to carry on with your usual eye drops as most of the time the laser is performed to have additional reduction in the pressure. It’s always advisable to check with your doctor if you have any doubts.

There are no major side effects or risks from this laser.

1. Your vision may be slightly blurred immediately after the laser. This usually clears in couple of hours. If you are concerned it is not returning to normal then get in touch with the hospital or clinic.

2. Your eyes may sometimes feel a bit bruised or you might get a slight headache. This is typically because of the lens touching your eye throughout the procedure. If you are able, you can take some paracetamol and get some rest to help.

3. Occasionally patients may get a transient spike in the eye pressure which usually settles but might need additional drops or tablets for few days.

As mentioned above, SLT is not a suitable treatment for everyone and for all types of glaucoma. It may not work in all patients. The success rate of the SLT laser is reported as 70%. The effect of the laser with regard to drop in intraocular pressure also varies from person to person. The effect is not immediate and it may take few weeks to reduce the intraocular pressure. The effect of the laser doesn’t last forever and in fact in 50% of the patients the effects wear off within 5 years. But because it doesn’t cause any damage the laser can be repeated in the same eye if the effects begin to wear off.


SLT is one of the treatment options for open angle glaucoma in addition to drops and surgery. It is non-invasive, quick and effective procedure with minimal side effects and risks. The effect of the laser can last for a few years and can be repeated if necessary.


While care has been taken to compile accurate information and to keep it up to date, Mr Agarwal cannot guarantee its correctness and completeness. The information provided in this information sheet is designed to support care and is not a substitute for professional healthcare advice, by a qualified doctor or other healthcare professional, which will be tailored to a patient’s individual circumstances.

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