SLT — laser treatment for glaucoma that can replace or complement eye drops

Glaucoma is one of the leading causes of irreversible sight loss, and its insidiousness lies in the fact that for a long time it causes no symptoms at all. The key to halting the disease is lowering intraocular pressure. For years the only first step was eye drops, but today an equal — and often more convenient — option is the laser procedure SLT (selective laser trabeculoplasty).

What does SLT involve?

Aqueous humour continuously fills the inside of the eye and must drain from it freely. In glaucoma the outflow through the so-called drainage angle (the trabecular meshwork) is impaired, so the pressure in the eye rises and damages the optic nerve.

SLT uses gentle laser pulses that precisely stimulate cells in the trabecular meshwork, improving the natural outflow of fluid. The word “selective” is key here: the laser acts selectively only on specific cells, without damaging the surrounding tissue. This makes the procedure safe and, if necessary, repeatable.

What does the procedure look like?

SLT is an outpatient procedure performed in the consulting room, with no need to stay at the clinic:

• the eye is numbed with drops — the procedure is painless,
• the doctor applies a special contact lens and delivers a series of laser pulses through the drainage angle,
• the whole thing usually takes a few to fifteen minutes,
• after a short observation the patient returns home and to everyday activities.

The pressure-lowering effect develops gradually over several weeks. Control measurements are sometimes needed to assess the response to treatment.

The greatest advantages of SLT

Fewer drops or no drops. In many patients SLT allows glaucoma drops to be stopped or their number reduced. This is a huge relief for people who forget to instil drops, tolerate preservatives poorly or use several preparations at once.

It solves the problem of adherence. The effectiveness of drops depends on daily, regular use — and in practice that varies. SLT works regardless of the patient’s memory.

Safety and repeatability. The procedure does not damage tissue, leaves no scars and can be repeated after years if needed.

It can be the first choice. SLT does not have to be a “last resort” — increasingly it is proposed at the very start of treatment, instead of beginning with drops.

SLT as first-line treatment — what do the studies say?

Until recently SLT was regarded as an option for patients in whom drops had failed. That was changed by the large multicentre clinical trial LiGHT (Laser in Glaucoma and Ocular Hypertension), published in the prestigious journal The Lancet in 2019. It included 718 patients with open-angle glaucoma or ocular hypertension, randomly assigned to treatment starting either with SLT or with drops.

The results spoke in favour of the laser:

• after 3 years as many as 74.2% of eyes treated first with SLT maintained target pressure without any drops,
• in the SLT group glaucoma surgery was needed less often, and adverse events were very rare.

Follow-up was extended to 6 years (published in Ophthalmology, 2023). It confirmed the durability of the effect and additionally showed that starting treatment with SLT was associated with slower disease progression (progression in 19.6% of eyes versus 26.8% in the drops group) and fewer glaucoma operations (13 versus 32 eyes). On this basis SLT is today recommended as first-line treatment, before drops.

SLT versus drops — fewer side effects

Glaucoma drops are effective, but used for years they can be a burden. Their active substances and preservatives (most often benzalkonium chloride) can lead to chronic irritation and redness of the eyes, dry eye syndrome, allergy and damage to the ocular surface. Some drugs also cause systemic symptoms — depending on the class, for instance a slowed heart rate, a drop in blood pressure or worsening of asthma.

SLT acts locally, once, and places no pharmacological burden on the body — which is why in the LiGHT trial the rate of adverse events was very low. For the patient this means not only convenience but also a lower risk of complications resulting from years of drop therapy.

Who is SLT for?

The procedure is considered, among others, in patients:

• with open-angle glaucoma or ocular hypertension,
• who want to reduce or stop drops,
• who tolerate glaucoma medication poorly (irritation, allergy, preservatives),
• in whom drops do not provide sufficient pressure control,
• who have difficulty instilling drops regularly and correctly.

Qualification is decided by an eye examination with assessment of the drainage angle, pressure and the condition of the optic nerve. SLT is not suitable for every type of glaucoma — which is why the decision is made by the doctor after diagnostics.

Important: SLT does not reverse damage

It must be said clearly: the laser lowers pressure and halts the progression of the disease, but does not reverse damage to the optic nerve that has already occurred. That is why early detection and regular monitoring are so important in glaucoma — lost visual field does not come back. It is one more argument for preventive eye examinations, especially after the age of 40 and with glaucoma in the family.

SLT at OKUMED

At our clinic in Gdynia we have a laser suite in which we perform SLT and other laser procedures (including iridotomy for glaucoma, capsulotomy for secondary cataract and laser treatment of the retina). We precede the procedure with full glaucoma diagnostics to assess whether SLT will be effective and safe in a given case.

Book a glaucoma consultation at OKUMED — Świętojańska 135/2, Gdynia, phone +48 882 650 299 or via ZnanyLekarz.

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Sources: Gazzard G. et al. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial. The Lancet, 2019. Gazzard G. et al. Laser in Glaucoma and Ocular Hypertension (LiGHT) Trial: Six-Year Results. Ophthalmology, 2023.

This article is for information only and does not replace a medical consultation.