Laser Trabeculotomy for Glaucoma (ELT/FLIGHT)

Key Points at a Glance

Laser trabeculotomy is a MIGS (minimally invasive glaucoma surgery) that increases aqueous humor outflow by penetrating the trabecular meshwork and creating channels into Schlemm’s canal. There are two types: intraocular excimer laser (ELT) and non-incisional femtosecond laser (FLIGHT). ELT combined with cataract surgery has been reported to be safe and effective with long-term results, while FLIGHT is a non-invasive new technology with promising early data.

1. What is Laser Trabeculotomy?

Laser trabeculotomy is a surgery that uses a laser to penetrate the trabecular meshwork and create a passage (channel) into Schlemm’s canal. It is classified as a trabecular laser procedure in MIGS (minimally invasive glaucoma surgery)¹⁾.

While selective laser trabeculoplasty (SLT) induces a biological effect on trabecular meshwork cells to enhance aqueous outflow, laser trabeculotomy fundamentally differs by physically creating channels.

Currently, there are two methods:

• Excimer laser trabeculotomy (ELT): An intraocular (ab interno) procedure using a 308 nm xenon chloride excimer laser
• Femtosecond laser image-guided high-precision trabeculotomy (FLIGHT): A non-incisional method that delivers femtosecond laser through the cornea

Minimally invasive glaucoma surgery has a moderate intraocular pressure-lowering effect compared to traditional filtration surgery but offers a superior safety profile¹⁾²⁾. Although trabeculectomy remains the most effective pressure-lowering surgery, the indications for MIGS are expanding for early to moderate open-angle glaucoma and ocular hypertension to reduce medication burden¹⁾.

Q How are ELT and SLT different?

A

SLT (selective laser trabeculoplasty) is a procedure that irradiates pigmented cells of the trabecular meshwork to induce cytokine release, biologically enhancing aqueous outflow. In contrast, ELT (excimer laser trabeculotomy) physically penetrates the trabecular meshwork to create channels into Schlemm’s canal. SLT is an outpatient procedure, while ELT requires an incision into the eye and is usually performed in combination with cataract surgery.

2. Excimer Laser Trabeculotomy (ELT)

Principle

ELT uses a 308 nm xenon chloride (XeCl) excimer laser to create microperforations between the anterior chamber and Schlemm’s canal. Because it is a non-thermal ablation with short pulses (20 Hz, 60–120 nanoseconds), damage to surrounding tissue and collector channels is minimized, and scar formation and inflammatory response are also reduced.

Procedure

A corneal paracentesis is created, and a disposable fiberoptic probe with an angled metal tip is inserted into the anterior chamber. Under gonioscopic guidance, the tip is placed in contact with the trabecular meshwork, and approximately 10 microperforations (about 0.2 mm in diameter) are created over a 90-degree range. After laser application, bubbles and a small amount of reflux bleeding are observed, indicating penetration of the inner wall of Schlemm’s canal. After the procedure, viscoelastic material is removed, and the wound is closed with corneal stromal hydration.

Efficacy

The safety and efficacy of ELT have been reported in multiple studies.

Study	Subjects	Follow-up	IOP change
Stodtmeister (2011)	166 eyes, ELT alone	1 year	26.4 → 16.9 mmHg
Stodtmeister (2013)	46 eyes, ELT alone	5 years	25.5 → 15.9 mmHg
Töteberg-Harms (2017)	113 eyes, PEA combined comparison	4 years	19→14 mmHg

It is often performed in combination with cataract surgery. In a study by Moreno Valladares et al. (34 eyes, mean follow-up 11.5 months), mean intraocular pressure decreased from 20.9 mmHg to 16.3 mmHg, and 81% of eyes were medication-free. In an 8-year follow-up by Riesen et al. (161 eyes), IOP significantly decreased from 19.3 mmHg to 15.4 mmHg, but no significant reduction in the number of medications was observed.

Complications

Reported complications of ELT are rare and mainly consist of clinically insignificant transient microhyphema. The frequency of serious complications is markedly lower compared to trabeculectomy.

3. Femtosecond Laser Image-Guided High-Precision Trabeculotomy (FLIGHT)

Principle

FLIGHT (ViaLase® Laser Technology) is a non-incisional method that delivers femtosecond laser pulses through the cornea to the iridocorneal angle, performing precise photodisruption of the trabecular meshwork. The fundamental difference from ELT is that it creates a passage connecting the anterior chamber and Schlemm’s canal without incising the eyeball.

Procedure

A portable gonioscopic camera is used to visualize the iridocorneal angle and select the treatment site. A coupling lens is fixed to the target eye with a suction ring and docked to the laser system. Using real-time gonioscopic video and OCT, the laser is aimed at the trabecular meshwork surface with micron-level precision, and treatment is activated with a foot switch.

Efficacy and Safety

In a prospective pilot study by Nagy et al. (11 patients, 18 eyes, 2-year follow-up), mean intraocular pressure decreased from 22.3 mmHg to 14.5 mmHg (p=0.00005). Approximately 82% of eyes achieved an IOP reduction of 20% or more from baseline. No serious adverse events such as vision loss, corneal edema, hypotony, hyphema, peripheral anterior synechiae, or IOP spikes were reported. At 24 months, clear channels were confirmed by gonioscopy and anterior segment OCT.

Q Is FLIGHT an invasive surgery?

A

FLIGHT is a non-incisional method that irradiates the laser through the cornea, requiring no incision in the eyeball. In this respect, it differs from ELT and conventional trabeculotomy, making it a less invasive procedure. However, at present, it is still in the preliminary research stage, and large-scale long-term data are not yet available.

4. Comparison with Conventional Trabeculotomy

External Trabeculotomy

Conventional trabeculotomy is a procedure in which a scleral flap is created, Schlemm’s canal is identified, and a metal probe (trabeculotome) is inserted into Schlemm’s canal and rotated to incise the trabecular meshwork. Complications include hyphema (almost inevitable), Descemet’s membrane detachment, cyclodialysis, and transient ocular hypertension. Postoperative intraocular pressure often ranges from 16 to 20 mmHg ³⁾.

Microhook Internal Trabeculotomy (MIGS)

This is one of the MIGS procedures that has rapidly gained popularity in recent years. It preserves the conjunctiva and sclera, and directly incises the trabecular meshwork under gonioscopy through a small corneal incision. It has short-term efficacy comparable to conventional external trabeculotomy, with less induced astigmatism and faster visual recovery. Simultaneous performance with cataract surgery is standard ³⁾.

Advantages of Laser Methods

ELT and FLIGHT enable precise tissue removal with laser compared to mechanical incision using conventional trabeculotomes or microhooks. In particular, FLIGHT does not require an incision in the eyeball and may be performed as an outpatient procedure in the future.

5. Latest Research and Future Prospects

Intraoperative gonioscopic image of laser trabeculotomy

Gabriel Ayub; Ticiana De Francesco; Vital Paulino Costa. Bent ab interno needle goniotomy versus gonioscopy-assisted transluminal trabeculotomy in primary open-angle glaucoma: study protocol of a randomized clinical trial. Trials. 2024 May 3;25:300. Figure 2. PMCID: PMC11069271. License: CC BY.

Intraoperative image showing the incision of the trabecular meshwork while viewing the angle. It indicates the position where the trabecular meshwork around Schlemm’s canal is incised.

Long-term Outcomes of ELT

An 8-year follow-up study by Riesen et al. demonstrated the long-term intraocular pressure-lowering effect of ELT combined with cataract surgery. However, the long-term reduction in the number of medications was limited, and some cases required additional treatment. Reoperation was reported to be rare.

Potential of FLIGHT

FLIGHT is the only laser trabeculotomy that does not require an incision in the eyeball. Pilot studies have shown safety and efficacy, but the number of patients was small and follow-up periods were limited. In the future, large-scale efficacy and safety data from randomized controlled trials are essential.

Reporting Standards for Minimally Invasive Glaucoma Surgery

In clinical trials of minimally invasive glaucoma surgery, there is a trade-off between safety and efficacy, and endpoint settings different from those of conventional filtration surgery are required ²⁾. Establishing standardized reporting standards is a future challenge.

Q Which patients are suitable for laser trabeculotomy?

A

Laser trabeculotomy as a minimally invasive glaucoma surgery is mainly indicated for patients with early to moderate open-angle glaucoma or ocular hypertension. It is particularly useful when performed concurrently with cataract surgery to reduce medication burden. For patients with advanced glaucoma or those requiring low target intraocular pressure, conventional filtration surgery is recommended.

Disclaimer

This article is intended to provide information to healthcare professionals and the general public and does not replace individual diagnosis or treatment. Please consult your ophthalmologist regarding surgical treatment for glaucoma.

6. References

1. European Glaucoma Society. Terminology and Guidelines for Glaucoma, 6th Edition. PubliComm; 2025.

2. American Academy of Ophthalmology. Primary Open-Angle Glaucoma Preferred Practice Pattern. 2020.

3. 日本緑内障学会. 緑内障診療ガイドライン(第5版). 日眼会誌. 2022;126:85-177.