Laser Suture Lysis after Trabeculectomy

Key Points at a Glance

Laser suture lysis (LSL) is a procedure in which the scleral flap sutures are cut transconjunctivally with a laser after trabeculectomy to gradually increase aqueous humor filtration. It is an essential postoperative management technique to gradually loosen the tightly sutured scleral flap, which is done to prevent early postoperative overfiltration, according to the postoperative intraocular pressure. It can be performed on an outpatient basis and contributes to achieving the target intraocular pressure.

1. What is Laser Suture Lysis?

Laser suture lysis (LSL) is a procedure in which a laser is applied transconjunctivally to cut the nylon sutures of the scleral flap after trabeculectomy¹⁾. It was reported by Lieberman, Hoskins, and Migliazzo, and involves visualizing the sutures using a compression contact lens and cutting them with a laser.

In trabeculectomy, the scleral flap is tightly sutured to prevent early postoperative overfiltration and hypotony. Subsequently, LSL is used to gradually increase filtration according to postoperative intraocular pressure to achieve the target pressure¹⁾. Although the use of mitomycin C (MMC) and 5-fluorouracil (5-FU) has improved surgical success rates, it has also increased the incidence of postoperative hypotony, making tight suturing with planned LSL even more important.

2. Indications and Contraindications

Indications

LSL is performed when aqueous humor filtration is judged to be insufficient¹⁾. Specific conditions include:

• Intraocular pressure does not decrease sufficiently despite ocular massage
• The filtering bleb is low, non-functioning, or failing
• Need to enhance early postoperative aqueous outflow²⁾

Contraindications

There are no absolute contraindications, but it is advisable to avoid the following conditions:

• When Tenon’s capsule is thickened and inflamed
• When there is subconjunctival hemorrhage at the trabeculectomy site
• When the conjunctiva is stained with fluorescein (which limits argon laser transmission and risks conjunctival burns)

Q In what cases is laser suture lysis performed?

A

It is performed when intraocular pressure remains above the target after trabeculectomy and adequate reduction is not achieved with ocular massage. By cutting the scleral flap sutures one by one, aqueous outflow is gradually increased to adjust intraocular pressure to the target range. It is a simple procedure that can be performed in the outpatient clinic under topical anesthesia.

3. Lens and Technique

Lens

All lenses are used to compress the conjunctiva, induce ischemia, and improve visualization of the sutures.

Lens Name	Features
Hoskins	Most common. Magnification 1.2x
Blumenthal	Snug compression with protrusion. Magnification 2-3x
Mandelcorn lens	Magnification 1.32x

If the conjunctiva is thin, apply surface pressure with a Hoskins lens. If the Tenon’s capsule is thick and difficult to visualize, use a Blumenthal lens to apply focal pressure for visualization.

Procedure

1. Administer topical anesthesia
2. If conjunctival injection is present, induce vasoconstriction with 2.5% phenylephrine
3. Have the patient look downward and lift the upper eyelid
4. Place the cutting lens directly over the suture and compress the conjunctiva to induce ischemia
5. Visualize the suture and apply laser
6. Cut one suture at a time. Start with the suture closest to the corneal limbus and leave the most distal one for last

After cutting, measure intraocular pressure and evaluate the filtering bleb¹⁾. If the effect is insufficient, add ocular massage with the same lens.

Laser Settings

Argon laser (most common)

Spot size: 50–200 μm

Power: 100–300 mW (low power if conjunctiva is thin)¹⁾

Irradiation time: 0.1–0.2 seconds¹⁾

Number of shots: 1–2 shots can cut through

Other lasers

Nd:YAG laser: 1064 nm or 532 nm

Diode laser: 840 nm

Avoiding conjunctival burns: Use of a red laser is preferable¹⁾

Multispot method: A technique to create a 250 μm “laser line” with 5 spots of 50 μm each has also been reported

4. Timing of procedure

Window period

Wait for 48 hours postoperatively due to the risk of overfiltration and hypotony. Hoskins and Migliazzo reported that LSL performed 1–3 weeks after surgery is effective.

Without antimetabolites, the acceptable window for LSL is within 2 weeks postoperatively (4 days to 3 weeks). Use of mitomycin C significantly delays wound healing, thus extending the period during which LSL can be performed.

However, as time passes after surgery, scarring around the scleral flap progresses, and the effect of LSL diminishes¹⁾. Even with mitomycin C, the suture-cutting effect diminishes 3 weeks to 1 month after surgery, and the longer the interval to LSL, the higher the long-term intraocular pressure tends to be¹⁾. In principle, after 1 month postoperatively, scarring of the scleral flap is complete and little effect can be obtained.

Importance of appropriate timing

To avoid missing the timing for LSL, follow-up examinations at appropriate intervals are necessary. On the first postoperative day, intraocular pressure is unstable and there is a risk of sudden drop; if the pressure is not significantly above 15 mmHg, first observe with massage. From 2–3 days after surgery, if bleb formation is poor or intraocular pressure exceeds 15 mmHg, promptly consider performing LSL¹⁾.

5. Complications

Notes on complications

The reported incidence of complications after LSL is approximately 30%. Cutting multiple sutures at once increases the risk of overfiltration, so it is important to cut sutures one by one in a stepwise manner, evaluating intraocular pressure and the filtering bleb each time ¹⁾.

Immediate complications

Conjunctival wound dehiscence: Caused by excessive manipulation of the conjunctiva and may require surgical repair. Conjunctival perforation: Occurs when laser is applied over a bleeding site. Small perforations heal within 24 hours.

Early complications

Hypotony: The most common complication, with an incidence of 18–35%. Avoid excessive massage immediately after laser. Usually resolves spontaneously.

Shallow or flat anterior chamber: Managed with cycloplegics, aqueous suppressants, and pressure patching.

Iris incarceration: If the peripheral iridectomy is small, rapid decompression may cause the iris to become incarcerated in the fistula. Requires surgical repair.

Malignant glaucoma: A rare complication caused by rapid decompression after suture cutting. Occurs within 48 hours postoperatively. High intraocular pressure with angle closure is a risk factor.

Late complications

Progressive lens opacification: Reported in 18% of cases. Giant filtering bleb: May be associated with dellen formation.

Q How many times can laser suture lysis be performed?

A

Typically, 2 to 5 sutures are used to fixate the scleral flap during surgery, and that number is the maximum number of cuts possible. Cut one suture at a time, evaluate intraocular pressure and the filtering bleb each time, and decide whether further cutting is needed. If intraocular pressure does not decrease sufficiently after cutting all sutures, needling or additional surgery may be considered.

6. Mechanism of action

Principle of filtration adjustment

Laser energy applied transconjunctivally melts and cuts the suture. This releases the compression at the scleral flap level and promotes aqueous humor outflow into the subconjunctival space.

In trabeculectomy, postoperative intraocular pressure is determined by the balance between aqueous humor production and outflow through the scleral flap into the filtering bleb ¹⁾. Surgical outcomes depend on early postoperative filtration adjustment and long-term inhibition of subconjunctival scarring, making LSL an important postoperative management element alongside surgical technique ¹⁾.

Algorithm for Early Postoperative Management

Before LSL, scleral massage is attempted first ¹⁾. If sufficient filtration is not confirmed with massage, LSL is performed. For high intraocular pressure, the posterior suture is cut to expand the bleb toward the fornix. Conversely, for hypotony due to overfiltration, atropine eye drops, transconjunctival scleral flap suturing, or autologous blood injection are considered ¹⁾.

7. Latest Research and Future Perspectives

Efficacy of Early LSL

A study by Mano et al. emphasizes the efficacy of early LSL from postoperative day 8 to week 12. It was performed in cases with intraocular pressure exceeding 10 mmHg, and effective IOP reduction was observed especially after the first LSL, with no increase in complication rates.

New Laser Technologies

A technique using a multi-spot laser system has been reported. It creates a 250 μm “laser line” by connecting five 50 μm diameter spots with a green laser (532 nm), and is considered useful when patient cooperation is difficult or the surgeon’s proficiency is insufficient.

Comparison with Releasable Sutures

Alternatives to LSL include releasable sutures and adjustable sutures ³⁾. Releasable sutures can achieve similar effects by being pulled out postoperatively, but LSL has the advantage of being performed non-invasively in an outpatient setting and allowing more flexible timing of suture cutting ²⁾.

Disclaimer

This article is intended for informational purposes for healthcare professionals and the general public, and does not substitute for individual diagnosis or treatment. Please consult your ophthalmologist for management after trabeculectomy.

8. References

1. 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.

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

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