Glaucoma Surgery Options: SLT, MIGS and Trabeculectomy Compared

Selective laser trabeculoplasty (SLT) is an in-clinic laser treatment that improves the eye's own drainage. It uses a 532-nm frequency-doubled Nd:YAG laser that targets pigmented cells in the drainage meshwork, which triggers a chemical response that lets fluid leave the eye more easily (EyeWiki, American Academy of Ophthalmology, AAO). It typically lowers eye pressure by about 20–30%.

SLT takes about ten minutes per eye under numbing drops, and most people feel no pain (Glaucoma UK). Your vision may be blurry for a few hours and the eye may be red and sore for a few days. You usually go back to normal activities the next day, and it takes two to three months to see how well it has worked.

The evidence for SLT as a first treatment is strong. In the UK LiGHT trial (Ophthalmology, 2023), 69.8% of eyes treated first with SLT were still at their target pressure six years later without needing drops or surgery. Disease progressed in fewer SLT eyes than drop-treated eyes (19.6% against 26.8%); 13 SLT eyes needed trabeculectomy against 32 drop eyes; and no serious laser-related adverse events occurred. Since 2022, NICE has recommended offering 360° SLT to people with newly diagnosed open-angle glaucoma that is not advanced, and to people with ocular hypertension and a pressure of 24 mmHg or more who are at risk of visual impairment.

Be aware of the limits. According to Glaucoma UK, SLT lowers pressure at first in nearly 8 out of 10 people, while about 2 in 10 get little or no benefit. The effect can wear off after a few years, but SLT can often be repeated, although fewer people reach good pressure after a second or third treatment. SLT may be unsuitable for advanced glaucoma or angle-closure glaucoma, and EyeWiki lists inflammatory and neovascular glaucoma as further exclusions. A short rise in pressure after the laser is the most important side effect, which is why your pressure is checked before you leave.

MIGS is a family of glaucoma operations done from inside the eye through a tiny incision, designed to be safer and quicker to recover from than traditional surgery. EyeWiki describes five defining features: a high safety profile, minimal disruption of normal anatomy, an ab-interno (from inside) approach, efficacy and ease of use.

The group includes several different ideas:

• Stents that bypass the blocked drain, such as the iStent family and the Hydrus microstent, which create a direct path into the eye's drainage canal.
• Tissue-removal devices, such as the Kahook Dual Blade, which remove a strip of the blocked drainage meshwork (goniotomy).
• Canal-opening procedures, which widen the eye's natural drainage canal.
• Subconjunctival stents, such as the XEN gel stent, which form a bleb and are closest to traditional surgery.

MIGS suits people with mild to moderate glaucoma, people who struggle to use drops, and people having cataract surgery who want to reduce their drops (EyeWiki). In the pivotal trials of stents placed during cataract surgery, 75.8% of iStent inject eyes and 77.3% of Hydrus eyes had at least a 20% fall in pressure at two years; with Hydrus the average fall was 7.6 mmHg compared with 5.3 mmHg for cataract surgery alone.

The honest limit is strength. MIGS typically lowers pressure by 20–30%, which is less than trabeculectomy, and EyeWiki notes it is often not enough for advanced glaucoma that needs a very low target pressure. Common side effects are temporary bleeding in the front of the eye (hyphaema), short pressure rises and inflammation. An NHS trust leaflet reports hyphaema in 38% of people during the Kahook Dual Blade operation, usually clearing in one to three weeks. Not every device has stood the test of time: the CyPass stent was withdrawn from the market, so your surgeon should explain which device they use and why.

Tube surgery is used when glaucoma is advanced or complex, when pressure stays high after other treatment, or after earlier eye surgery. A tiny silicone tube carries fluid to a plate that sits under the surface of the eye, where a bleb forms (Glaucoma UK). Common devices are the Ahmed valve and the Baerveldt, PAUL and Molteno implants. Five years after surgery, Glaucoma UK reports that shunts still work well for more than 7 in 10 people.

Which is better, a tube or a trabeculectomy? It depends on the eye, and large trials give different answers:

• In eyes that had already had cataract or glaucoma surgery, the Tube Versus Trabeculectomy (TVT) study found failure was less likely with a tube: 29.8% against 46.9% at five years, with similar pressure reduction (American Journal of Ophthalmology, 2012).
• In eyes with no previous surgery, the Primary Tube Versus Trabeculectomy (PTVT) study found that trabeculectomy with mitomycin C failed less often, with similar pressure control but fewer drops (AAO summary: 39% of trabeculectomy patients against 48% of tube patients had surgical failure at five years). Early complications were more common after trabeculectomy (34% against 19%), and most were temporary (Ophthalmology, 2022).

All glaucoma surgery carries risks, and your surgeon should go through those that apply to your eye before you decide.

• SLT: blurred vision for hours, a red and sore eye for days, and a short rise in pressure in a minority of people (EyeWiki puts a rise of more than 5 mmHg at around 10% or fewer when preventive drops are used). Inflammation is a small risk. LiGHT reported no serious laser-related adverse events over six years.
• MIGS: bleeding in the front of the eye, short pressure spikes, inflammation and low pressure. Serious complications are rarer than after traditional surgery (EyeWiki).
• Trabeculectomy: pressure that is too low or too high early on, which may need stitch adjustment or a small procedure; faster cataract formation; infection inside the eye in about 1–2 in 100 people; and about 1 in 10 people notice a one-line drop on the eye chart a year later (Dudley NHS leaflet). In the PTVT study, serious complications causing vision loss or needing another operation affected 8% of trabeculectomy patients and 2% of tube patients.
• Tube surgery: blurry vision for up to three months is common; serious or sudden vision loss affects fewer than 1 in 100 people, with a higher risk in advanced glaucoma; about 1 in 50 people has a droopy eyelid for longer, which can usually be corrected (Glaucoma UK).
• More surgery: some eyes need a second operation. In the TVT study, 29% of trabeculectomy eyes and 9% of tube eyes needed further glaucoma surgery within five years.

The risk of not treating also deserves a place on the scale. Glaucoma damage is permanent, according to the AAO, and uncontrolled pressure keeps damaging the optic nerve.

Glaucoma is a lifelong condition, so the most useful question is who looks after your eye pressure once you are home. Before you travel, plan three things: that you receive a full operative report in English for your home eye doctor, that your follow-up visits are agreed in advance, and that you can reach the surgical team remotely if something changes.

At Laser Istanbul Clinic, your surgery takes place in a fully equipped, Ministry of Health–licensed operating theatre in Istanbul. Your price includes the pre-operative examination and scans, surgery by your named surgeon, medication, follow-up checks in Istanbul, a personal interpreter, a coordinator and remote follow-up. Hotel and airport transfers are not included; we arrange them on request at a separate charge. Flights are not included either.

Flying is usually fine: Glaucoma UK notes that people with glaucoma can usually fly without problems and that it is safe to fly after glaucoma surgery, but your specialist may want to see you for follow-up first, so wait until they say it is okay. Keep your drops in your hand luggage.

If your glaucoma goes together with a retinal problem, see our guide to Retina surgery: vitrectomy & retinal detachment.