What is selective laser trabeculoplasty?
There are a number of treatment options available to lower the eye pressure (intraocular pressure) in open angle glaucoma and ocular hypertension including intraocular pressure lowering drops (referred to as drops), laser treatment and surgery. Selective laser trabeculoplasty (SLT) is one laser option for lowering the intraocular pressure (IOP) for patients who have open-angle glaucoma (OAG) or raised intraocular pressure without glaucoma (ocular hypertension -OHT).
How does selective laser trabeculoplasty work?
The predominant drainage system of the eye is called the trabecular meshwork (TM). In open angle glaucoma or OHT, this system is believed to be ‘partially blocked or non-functioning’.
The laser treatment is aimed directly at the trabecular meshwork (hence the name ‘selective’) to improve drainage through it. It works by using short pulses of low energy of laser to target pigment rich (melanin) cells within the TM. This allows for only these cells to be treated, leaving surrounding tissue intact. The net effect of this treatment is to induce a chemical response from the body, which can result in an increase in drainage of fluid (aqueous humour) from the TM and thereby a lowering of the IOP.
The treatment can take up to 6 months for the IOP lowering to take effect.
Is this the right treatment for me?
SLT can not only lower the IOP in the eye but can also reduce the degree of variability in the IOP (so called “fluctuation”) which has been shown to be a risk factor for worsening of glaucoma.
It may be suitable for you if:
1. You cannot manage to instill your drops as advised
2. The drops are causing side effects or allergies which are not tolerable
3. The drops are not effective
4. Additional IOP lowering is required and drops are not an option
How successful is selective laser trabeculoplasty?
Studies show that SLT can induce a reduction in the IOP by up to 30%. This magnitude of effect is similar to the most common type of drop we use for glaucoma (prostaglandin analogue). The degree to which SLT lowers IOP is influenced by various factors including age, eye pressure before SLT, previous glaucoma treatments and glaucoma severity. The response to SLT may take up 6 months to take effect.
In terms of duration of effect, studies have shown that after a single treatment, SLT is deemed to be successful (with no additional treatment being required) in up to 40-60% patients at 4 years.
Although the effect of SLT can wear off with time, the treatment can be repeated. However, although SLT can still lower the IOP when repeated, the magnitude of effect may not be as much as the initial treatment.
A large trial (LiGHTtrial) comparing eye drops to SLT has shown that at 3 years following SLT treatment, 78% of eyes achieved their predetermined target IOP with 76% achieving this with one treatment alone. Additionally, 74% of patients were drops free at 3 years. Compared to the eye drops only group, patients in the SLT laser group had lower rates of glaucoma deterioration and no patients required glaucoma surgery (trabeculectomy).
There is a chance that this procedure will not lower pressure at all (approximately 20% of patients). If SLT doesn’t work it is likely that eye drops to reduce pressure will need to be increased. If this doesn’t sufficiently lower the eye pressure, glaucoma surgery may be required.
SLT does not cure glaucoma, just as medication and surgery do not. Continual follow-up and monitoring with an ophthalmologist is essential.
Are there any risks or side effects of treatment?
SLT laser has a track record of safety for over two decades; however, there may be uncommon side effects.
1. Transient blurred vision: Your vision may be blurred from a few hours upto 24 hours but, the chance of your vision being permanently affected from SLT is extremely small. If you are concerned thatyourvision is not returning to normal, please contact us or attend your local eye emergency department.
2. Transient eye discomfort/ light sensitivity/ redness of the eye: This is not uncommon for the first 2-3 days after the laser. Should you experience these symptoms, you can take paracetamol or ibuprofen providing you are not allergic or intolerant to these. Sometimes we may prescribe an anti-inflammatory drop for a few days.
3. High intraocular pressure (IOP): It is possible for the IOP in your eye/eyes to increase immediately after the treatment (1-2% of eyes). If this occurs, you will be advised to use additional drops or tablets to lower the eye pressure.
4. Reduced vision: This is a very rare side effect and should you experience this, you should contact us as soon as possible or attend your local eye emergency department.
Stopping certain eye drops before selective laser trabeculoplasty
Certain eye drops share a common mechanism of action to the SLT laser. Therefore, you MAY (at the surgeons discretion) be asked to stop them for at least 4 weeks prior to the SLT laser treatment and not to use them after the laser treatment. The drops you may be asked to stop are: Latanoprost (Xalatan / Monopost); Bimatoprost (Lumigan);Tafluprost (Safi utan) or Travaprost (Travatan). As you may be using some of the above drops in combination form, you may be advised to modify them as well.
The day of treatment
Please ensure you are not driving after the procedure and therefore make arrangements for your collection. The treatment takes place in the outpatient department. Your vision and eye pressure (IOP) are checked and then IOP lowering drops are instilled into your eye. These drops take up to 30 minutes to take effect. The doctor will then take your written consent and explain further if you have any questions. Once seated in front of the laser machine, which looks similar to the microscope you will have been examined on at your consultancy, you will have anaesthetic drops put in to numb the front of your eye. These will sting for a short while following instillation.
It is very important for you to:
Any movement might defocus the laser and it may not work as well as it should.
A special lens (with ‘cold’ gel on it) will then be placed against the front surface of your eye. This is not painful, but you may feel a little pressure. During the laser treatment, you might see some flashes of light and hear clicking noises. Most patients tolerate the laser treatment well, but some might feel slight discomfort. The procedure takes between 10 and 15 minutes per eye. The doctor will put some more pressure lowering drops in at the end of the laser procedure.
We will make an appointment for you to come back to the clinic, usually two to six weeks later. This follow-up appointment is to check your eye pressure and that your eye is settling.
What happens after the laser?
The pressure in your eyes will be checked 30-60 minutes after the laser. If the pressure in your eyes is not significantly elevated after 30-60 minutes you will be able to go home. If the eye pressure is very high, further treatment (in the form of drops or tablets) to lower the pressure may be necessary before you can go home.
Should you experience any discomfort then you can take either paracetamol or ibuprofen tablets providing you are not allergic to or intolerant of these medications. Sometimes we prescribe anti-inflammatory drops for a few days if we anticipate you may need these.
Regarding your glaucoma drops you will have been advised to either continue or stop them prior to the laser. If you are unsure, please clarify with the doctor either at the time you are listed for the laser or on the day of the laser.
We will then arrange to see you in approximately 2-6 weeks after the laser (depending on your condition). Further follow-up will then be decided at this time.