SLT laser
SLT stands for selective laser trabeculoplasty. It is a laser treatment that lowers the pressure inside the eye.
For many years laser was offered only after eye drops had stopped working. The evidence has changed, and SLT is now often used as a first treatment, before any drops are started.
How it works
A low-energy laser is applied to the trabecular meshwork, the eye's natural drainage filter, through a contact lens placed on the front of the eye.
The treatment is described as selective because the laser affects only the pigmented cells in the filter. The energy is too low to burn or scar the surrounding tissue. It does not make a hole. It appears to work by prompting the filter to remodel itself, which improves drainage.
Because no scarring occurs, SLT can be repeated if the effect wears off.
What the evidence shows
The LiGHT trial, published in The Lancet in 2019, compared starting treatment with SLT against starting with eye drops in people newly diagnosed with open angle glaucoma or ocular hypertension.
After three years, around three quarters of the people treated with SLT did not need any eye drops. Their pressure control and quality of life were at least as good as those who started on drops, and the approach was more cost-effective.
Follow-up published in 2022 found that after six years, people who started with SLT had more stable disease and needed less glaucoma surgery than those who started with drops.
The laser used at the clinic
SLT is carried out using an A.R.C. Laser CITO 532, a German-made SLT laser, and the treatment is performed by Dr O'Regan personally.
Most SLT lasers use flash lamp technology, which limits how quickly pulses can be delivered. The CITO 532 uses newer micro-chip technology, giving a faster pulse rate and a more uniform laser spot. In practice this means treatment is quicker and more consistent. The laser is on site, so there is no separate referral or waiting list for it.
Is SLT suitable for me?
SLT works in open angle glaucoma and ocular hypertension. The drainage angle needs to be open for the laser to reach the filter, which is checked by gonioscopy at your assessment.
It is worth considering if:
- You have been newly diagnosed and would prefer not to start daily drops
- You find drops difficult to put in, or often forget them
- You are getting side effects from drops
- Your pressure is not controlled and you would rather not add another bottle
It is less suitable for angle closure glaucoma, for some secondary and inflammatory glaucomas, and where the pressure needs to be lowered a great deal very quickly.
About one in five people do not respond to their first treatment. This does not mean anything has gone wrong. It means a different approach is needed.
What happens on the day
SLT is done in the outpatient clinic. You are not admitted and no injections are needed.
Before. Continue your usual drops unless you are told otherwise, and eat normally. You will usually be given a pressure-lowering drop beforehand.
During. Anaesthetic drops numb the surface of the eye. A contact lens with gel is placed on the eye to focus the laser, which feels like pressure rather than pain. You sit at a machine similar to the one used for a routine eye examination, with your chin on a rest. You will see flashes of light and may hear small clicks. Treatment takes about five minutes per eye. Most people find it easier than they expected.
After. Your vision will be blurred for an hour or two from the gel. The eye may feel gritty and look slightly red for a day. You will usually be given anti-inflammatory drops for a short period, and your pressure is checked about an hour later and again a few weeks afterwards.
Driving. Do not drive yourself home, as your vision will be blurred. Arrange a lift. You can usually drive normally the next day.
Work. Most people return to normal activities the following day.
What to expect afterwards
The effect is gradual. Some pressure reduction appears within a few weeks, but the full effect can take up to three months. Do not judge the result at your first check.
Do not stop your drops unless told to. If drops are to be withdrawn, this is done deliberately with your pressure monitored.
The effect wears off over time, usually after three to five years, though this varies. When it does, the pressure gradually rises again. This is picked up at your routine appointments rather than by anything you would notice, and the treatment can usually be repeated.
You still need regular monitoring. SLT lowers pressure but does not cure glaucoma.
Contact the clinic if you develop worsening pain, significant loss of vision, or an increasingly red and light-sensitive eye. Serious problems are uncommon. A short-lived rise in pressure in the first few hours is the main early risk, which is why your pressure is checked before you go home.
Next steps
Patients — contact the clinic to arrange an appointment.
GPs and optometrists — refer directly to Limerick or Ennis, including by Healthmail.