What is Selective Laser Trabeculoplasty (SLT)?
SLT is a laser treatment for glaucoma. It was first reported over 20 years ago in America by Mark Latina and co-workers. Uptake of SLT in the UK has been relatively slow, but adoption is increasing following the results of a landmark clinical trial in the UK which announced surprisingly favourable results for the laser treatment in March 2019.
How does SLT work?
SLT laser is aimed directly at the trabecular meshwork, which is the part of the eye that drains fluid. The laser energy – delivered in pulses each lasting a tiny fraction of a second – activates the body’s cells to clear up debris from the meshwork and this increases the amount of fluid that the eye can naturally drain, which brings eye pressure down.
Who is suitable for SLT?
SLT is suitable for anybody with open-angle glaucoma, or ocular hypertension which is at risk of conversion to glaucoma. It can be used as first-line therapy, or alternatively to help reduce pressure in patients with inadequate response to (or intolerance of) glaucoma eye drops.
Who is not suitable for SLT?
SLT is not suitable in eyes with a history of significant inflammatory disease (uveitis), or eyes where narrow iridicorneal angles / primary angle closure would make the view of the trabecular meshwork difficult. It should also be avoided if previous SLT therapy has caused complications such as a spike in eye pressure. Finally, it is usually not considered beneficial to repeat SLT treatment if an initial complete SLT treatment (360 degrees) has achieved no pressure reduction at all.
How effective is SLT?
In recent clinical trials (the LiGHT study, published in The Lancet in 2019), SLT treatment was the only therapy required to achieve target pressure control for up to 3 years in three-quarters of patients. This means that for newly diagnosed open-angle glaucoma or ocular hypertension that meets treatment guidelines, there is a 75% chance that SLT treatment will be the only therapy needed for at least 3 years. This represents a large saving in inconvenience and side-effects from the daily eye drops for glaucoma which many patients have traditionally been prescribed straight away following diagnosis.
What will happen during my SLT procedure?
You will be awake and sitting upright at the special laser microscope. Mr Shah will apply a drop to prevent a spike in pressure due to treatment, as well as numbing eye drops and sometimes a pupil-constricting drop. A special contact lens called a goniolens is then applied to the eye surface. This allows Mr Shah to access the trabecular meshwork – the part of the eye which drains fluid. The laser treatment consists of several individual laser applications. The whole treatment takes less than 15 minutes. In certain eyes at high risk of a spike in pressure after treatment (for example eyes with very pigmented meshwork), Mr Shah may only treat 180 degrees (half way around) in the first session, in order to prevent a troublesome pressure spike, and then treat the other half at a later date. Your vision may be a little blurred for a few hours or for the rest of the day, but should then return to normal. The treatment is not painful.
How long does it take for the SLT treatment to work?
It can take 6-12 weeks for the maximum pressure reducing effect to become apparent.
Can SLT be repeated?
Yes, SLT can be repeated and this is frequently done where the initial SLT treatment worked well but where the effect has started to wear off, or alternatively where the first treatment has led to a partial response and the desire is for a greater pressure reduction. SLT is generally not repeated if the first treatment either had no effect whatsoever, or was associated with complications such as a protracted spike in pressure.
What are the side-effects of SLT?
Side-effects are uncommon. They include redness, pain/discomfort, and transient pressure elevation. These each have an incidence of about 1 in 20, and they can be treated with eye drops or tablets. Pressure elevation typically lasts less than 24 hours and is usually not clinically significant. Patients with risk factors for pressure elevation may be more suited to fractionated treatment (where half of the meshwork is treated at a time). Rare side-effects include corneal oedema in less than 1% of cases (swelling of the clear window at the front of the eye); hyphaema (anterior chamber haemorrhage); and macular oedema (swelling in the central part of the retina). All of these are usually treatable. Most patients do get some inflammation in the front chamber of the eye, which indeed is expected from the treatment and relates to its mechanism of action. Prolonged inflammation (iritis) has been described, and is normally treatable if necessary.
How long does the pressure-lowering effect of SLT last?
This can vary from 1-5 years, but in some patients, up to 10 years.
Can SLT treat normal tension glaucoma (NTG)?
Yes, it can. In NTG, SLT treatment can both reduce eye pressure and the burden of glaucoma drops. It can also reduce fluctuation in eye pressure in NTG patients.
What is the recovery period after SLT treatment?
You would be advised to bring a driver so that you are not driving home after the treatment. Most people can resume normal activities, including returning to work, within 1-4 days after treatment.
What if the SLT doesn’t lower my pressures at all?
If you haven’t already tried them, the next step would be pressure-lowering eye drops, which need to be instilled every day. If you have already been on drops which either didn’t work or produced troublesome side-effects, Mr Shah will discuss a variety of other possible interventions with you to reduce the eye pressure.
If SLT doesn’t lower my pressures, does it make pressure-lowering eye drops less likely to work?
No, there is no evidence that SLT diminishes subsequent efficacy of pressure-lowering eye drops.
Can I have SLT treatment if i am already on pressure-lowering drops?
Yes, but depending on which drops you are taking, SLT may not work as well. In particular, patients taking prostaglandin analogue glaucoma drops may find that the SLT doesn’t work as well as patients taking other types of glaucoma drop or no glaucoma drops at all. This is felt to be the case because SLT and prostaglandin analogue drops probably have a similar mechanism of action in lowering eye pressure.
Does SLT on one eye reduce pressure in the other eye?
Amazingly, there is some evidence that it might do this, supporting the theory that the response to SLT is a biologic one rather than a mechanical one, although the study cited is not brilliant evidence of this effect due to its small size and retrospective nature.
Can SLT treatment be performed in Jersey?
In late 2019 Mr Shah was delighted to welcome a brand new, FDA-approved laser device manufactured by Quantel Medical to his private practice based at Evolution Eye Care (Little Grove Clinic) in St Lawrence. Since this is the first SLT machine on Jersey, it represents a big step forward in glaucoma care for islanders. The laser suite at Evolution Eye Care is fully laser safety approved and is inspected regularly by Laser Protection Advisors from the UK.