Glaucoma can sometimes be treated successfully with medications to lower the pressure in the eye. If medications are not effective, laser and other surgical procedures could be of value in controlling the pressure and preventing further vision loss. Both medications and surgery are designed to do one of two things:
- Decrease the amount of fluid production in the eye from the cells that make the fluid
- Help the fluid flow out of the eye
Selective laser trabeculoplasty (SLT) is one option for lowering intraocular pressure (IOP) for people who have early stage open-angle glaucoma. It can also be used in people who have ocular hypertension (OHT), who are at risk of developing glaucoma in the future if their eye pressure is not reduced.
It can be used for patients who are not on any eye drops, if drops have failed to work previously, or used in combination with drops. It is a flexible treatment option and can be repeated if necessary, depending on how well you respond to it.
How it works
Your eyes naturally produce a clear fluid (called aqueous fluid) which helps to keep them healthy. This fluid drains away out of the eye through tiny pores at the edge of the coloured part of your eye (iris), through a drainage system called the trabecular meshwork. In glaucoma, this drainage can become less efficient causing the eye pressure to rise.
SLT treatment uses gentle, low energy laser pulses to treat this trabecular meshwork area direcltly. It targets specific cells in the trabecular meshwork, without affecting the surrounding structures. The laser helps to clear and “refresh” the drainage pores, so that fluid can flow out more easily. As a result, the pressure inside the eye is lowered.
Benefits
Using eye drops every day can be difficult. They can be tricky to put in, easy to forget and on occasion can cause eye irritation or allergic reactions.
Selective laser trabeculoplasty treatment lowers eye pressure without these difficulties or side effects. SLT is a newer form of a long- established treatment, has excellent success rate and very rarely causes any side effects or complications.
The treatment procedure
Treatment takes place in the outpatient department. A nurse will check your vision and put some drops in your eye to prevent the pressure rising after the laser. A laser specialist will take your written consent and if you have any questions, will explain further.
The laser machine looks similar to the slit lamp microscope you will have been examined with in clinic. Before starting, anaesthetic drops will be instilled to numb the front of your eye. A special lens will then be placed against the front surface of your eye. This is not painful, but it might feel a little unusual. During the laser treatment, you might see some flashes of light and hear clicking noises. Most patients do not feel any pain, but some feel slight discomfort. The procedure takes between 10 and 15 minutes.
About an hour after your treatment, a nurse will check your eye pressure again. You will be given a prescription for anti-inflammatory drops but you will only need to use them if the eyes become red, painful, or sensitive to light (most patients do not need to use these drops). We will make an appointment for you to come back to the clinic, usually two months later, to see if the laser has worked.
Success rate
A large UK study, called the LiGHT Trial, that was carried out at Moorfields and other hospitals, compared SLT and eye drops. It found that 3 out of 4 patients (74%) who had SLT did not need any other treatment for at least three years. In the other patients, it did not work well enough for their eyes and they required glaucoma drops. Usually, we cannot predict how well the laser will work with each patient.
If you are already using eye drops, you will usually need to continue these after the laser until we know how well the treatment has worked for you. At your follow up appointment, your specialist will explain whether you need to continue, reduce or stop your eye drops.
Some patients require a repeat treatment with SLT if the pressure is not at a sufficiently low level after their first laser treatment. Whether you need further SLT treatment will be determined at your follow up.
The effects of the SLT treatment might wear off over time (about half of all treatments stop working after five years). However, the treatment can be repeated if this happens.
Potential side effects
Your vision will be slightly blurred for a few hours following your laser treatment, but this should return to normal shortly afterwards. You are also advised not to drive yourself to the hospital, as you will be unable to drive home.
The chance of permanent damage to your vision being from SLT is extremely small.
It is possible for the pressure in your eye to increase immediately after the treatment and for the eye to become inflamed. To help prevent this, you will be given eye drops before the procedure. As noted above, we also provide anti-inflammatory drops (to be used if required), and occasionally extra glaucoma drops following your treatment should you need them.
Rarely, the pressure in the eye can rise a lot after SLT and may not come down. If this happens, you might require surgery to lower the pressure. However, please be assured that this is a very rare occurrence.
After your laser treatment, if you notice any sudden worsening of your vision, severe eye pain, headache or nausea, please come immediately to the Moorfields A&E department in City Road for a further examination (open 24/7 for emergency eye problems only). You can also call Moorfields Direct for urgent clinical advice.
video transcript
Welcome to this short information video on Selective Laser Trabeculoplasty, or SLT. Over the next few minutes, we will explain the procedure, why it has been offered to you, the benefits we hope to achieve, and the potential side effects of the treatment.
SLT is a laser treatment that helps to lower the eye pressure. It is performed in the outpatient clinic, in a designated laser room. There are no specific instructions for before the procedure, and people who are due to have the laser should continue to use their normal treatments unless specifically instructed otherwise. Half a day should be set aside for the procedure, and plans should be made for getting home with someone to help, as driving is not permitted.
You will come to your appointment and have your usual vision and eye pressure checks. Several different eye drops will be administered – these include a drop which helps reduce the eye pressure, as well as one which will numb the surface of the eye to make the laser procedure more comfortable.
Your clinician will answer any remaining questions you may have and take written consent. The laser treatment is then performed, through a slit lamp – like the microscope that is normally used for eye examinations – connected to the laser machine. A lens will be placed against the surface of the eye to improve the clinician’s view of the treatment area and stop the eye from closing. During the laser, you may hear some clicking noises and see flashes of light. The procedure takes between 5 to 7 minutes per eye and most people usually tolerate it well, although you may feel a little discomfort.
So why have you been offered this procedure? SLT is a laser procedure which applies low-energy light to specific cells in the drainage channel – called the trabecular meshwork – of the eye. The laser pulses affect only these cells, with the surrounding structure remaining unaffected. This gentle laser induces a response from the body to rebuild the trabecular meshwork so that it functions effectively again, reducing the eye pressure. The aims of the treatment vary for each individual patient and SLT is successful in around 80% of people.
Following the laser, you will then remain in clinic for 1 to 2 hours, to have your pressures checked again, before going home. If there is a significant rise in the eye pressure, this will be treated with additional drops and tablets if needed.
You will then be discharged home and will be asked to continue any usual treatment. The eyes may feel a little sore and the vision will be blurry; this is expected and will settle within 24 to 48 hours.
You will have a follow-up appointment 6 to 8 weeks later, to evaluate the success of your laser treatment and decide on the next steps.
The main benefits of SLT are that it lowers the eye pressure, which aims to help control your eye condition, and it may reduce or delay the need for eye drops or surgery.
While SLT is generally very safe, every procedure can carry some risks and side effects. Some people experience temporary blurred or cloudy vision, which usually clears within a few hours to a few days. Permanent changes to your vision are extremely rare. If you’re worried that your vision hasn’t returned to normal, please call us using the number at the end of the video.
A temporary rise in eye pressure occurs in around 1 in 10 patients. In very rare cases, the pressure may rise more significantly and may need further treatment. However, this is extremely uncommon, and your clinical team will monitor you closely to manage any changes. Inflammation can also occur and is usually treated with anti-inflammatory eye drops.
In around 20% of patients, the SLT treatment does not work. If the response is deemed to be inadequate, you may require additional treatment which may include repeat laser, eye drops, or eye surgery and this will be discussed with you by your clinician. Also, the effects of the laser treatment might wear off over time – about half of all treatments stop working after five years. However, the treatment can be repeated.
SLT is now recommended to be used as first-line therapy for those with ocular hypertension, and early open-angle glaucoma. This recommendation has come following the LiGHT Trial. This is a trial that compared eye drops with SLT as the initial treatment for these conditions in over 700 patients. The study showed that the vision and the eye pressure were similar in the two groups and that the group who had SLT required less glaucoma surgery and that some patients were spared from using glaucoma eye drops. You may have been offered SLT despite a different diagnosis, and your clinician will discuss this with you.
Thank you for watching this short informational video on SLT. If you have any questions, please feel free to raise these with your clinician at your next appointment. We hope you found this video useful and would appreciate your feedback.
Authors: Sana Hamid, Zain Juma, Emma Jones, Hari Jayaram and Gus Gazzard, Glaucoma Service
Review date: March 2028