Selective Laser Trabeculoplasty

Selective laser trabeculoplasty (SLT) is a laser treatment option for lowering the intraocular pressure (IOP) for patients who have open-angle glaucoma (OAG) or raised intraocular pressure (IOP) without glaucoma (ocular hypertension).

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 enhance drainage though it. It works by using short pulses of low energy of laser to target pigment (melanin) rich 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 of drainage of fluid (aqueous humour) from the TM and thereby lower the IOP.

Studies show that SLT can induce a reduction in the IOP by up to 30%. This magnitude of effect is similar to the commonest type of drop we use for glaucoma (prostaglandin analogue). The degree to which SLT lowers the 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 durations of effect, studies have shown that after a single treatment, SLT is deemed to 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 repeat SLT can still lower the IOP when repeated, the magnitude of effect may not be as much as the first treatment.

A large trial (LiGHT trial) comparing eye drops to SLT has shown that at 3 years following SLT treatment, 78% of eyes achieved their pre-determined 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 group, patients in the SLT laser group had lower rates of glaucoma deterioration and no patients required glaucoma surgery (trabeculectomy).

There is a small 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 are essential.

SLT laser has a safety track record for over two decade, however, there are several risks of the laser which are as follows:

1. Transient blurred Vision: your vision may be blurred from a few hours up to 24 hours but, the chance of your vision being permanently affected from SLT is extremely small. If you are concerned that your vision 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. Sometimes we may prescribe an anti-inflammatory drop for a few days following the laser.

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. Reduce 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.

5. Failure: Sometimes the laser fails to reduce your eye pressure sufficiently. If this occurs, further treatment options will be discussed with you.