01Purpose and principlesWhat the treatment does and how it fits into care.
Glaucoma procedures can improve existing outflow, create a new route for aqueous drainage or reduce aqueous production. These are different interventions, not interchangeable forms of a single operation. The appropriate choice depends on angle anatomy, disease severity, the pressure reduction required, prior treatment, ocular comorbidity and the person's ability to attend aftercare. Explaining the mechanism helps patients understand why a laser offered to one person may be unsuitable for another.
The goal is usually to preserve remaining vision by reducing the risk of further optic nerve damage. A pressure-lowering operation does not regenerate lost nerve fibres. Cataract surgery can improve vision attributable to lens opacity, but this should be distinguished from its possible pressure or anatomical benefits. Consent should therefore address the expected pressure effect, the possibility of ongoing drops or further procedures, relevant complications and the practical demands of recovery.
Key points
- SLT acts on the trabecular drainage system; peripheral iridotomy creates an iris opening to relieve pupil block; cyclodiode reduces aqueous production.
- NICE offers initial 360-degree SLT for eligible non-advanced chronic open-angle glaucoma and higher-risk ocular hypertension, with pigment dispersion excluded from this routine initial offer.
- Advanced chronic open-angle glaucoma merits an offer of augmented glaucoma surgery rather than a requirement to exhaust every drop first.
- Trabeculectomy creates controlled drainage beneath the conjunctiva, while a tube device directs fluid towards a reservoir around a plate.
- Angle-based microinvasive procedures and bleb-forming operations have different mechanisms and risk profiles; a smaller incision does not guarantee the pressure target needed for advanced disease.
- Pressure spikes, inflammation, hypotony, scarring and infection are relevant procedure-specific risks; early aftercare is part of the treatment.
- Continue or stop existing glaucoma drops only according to the written postoperative plan, and maintain long-term surveillance even after a successful procedure.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
Progression despite appropriate treatment, an insufficient pressure response or advanced disease at diagnosis should prompt a procedure discussion tailored to the required level of control.
Drop intolerance or physical difficulty administering treatment can support consideration of laser or surgery, while preserving the need for monitoring and postoperative support.
Unexpected worsening pain, visual decline, discharge or marked redness requires examination for pressure problems, inflammation, leakage or infection rather than reassurance by telephone alone.
Scarring may reduce drainage and raise pressure, while leakage or excessive filtration can cause low pressure; the appearance must be interpreted with pressure and anterior chamber findings.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Mechanism and angle assessment before selecting a procedureFirst step - Why
- Determine whether the proposed treatment reaches an appropriate outflow pathway.
- Interpretation and limitations
- An angle-based procedure needs accessible suitable anatomy; an iridotomy addresses pupil block, whereas it will not correct every secondary forward-displacement mechanism.
- 02
Baseline pressure, fields and optic nerve documentation - Why
- Define the disease stage and the pressure reduction required.
- Interpretation and limitations
- An apparently moderate pressure may still be unacceptable in an eye progressing near fixation; operative decisions should use visual reserve and disease trajectory.
- 03
Preoperative ocular and general medical assessment - Why
- Identify surgical, anaesthetic and aftercare factors that affect the plan.
- Interpretation and limitations
- Assess the conjunctiva, cornea, lens, inflammation, previous surgery and medicines, including anticoagulants; do not instruct routine anticoagulant interruption without the operating team's individual plan.
- 04
Postoperative slit-lamp examination and pressure - Why
- Identify leakage, inflammation, chamber change and inadequate or excessive drainage.
- Interpretation and limitations
- Interpret pressure with the wound, bleb or tube position and the visual symptoms; a very low pressure is not automatically a successful outcome.
04Treatment approachPreparation, options, escalation and aftercare.
01Initial laser optionOffer SLT to an eligible open-angle patientFirst stepA person has newly diagnosed eligible non-advanced disease or is considering laser to reduce treatment burden.+
- 1Confirm open-angle anatomy and NICE eligibility, and explain that SLT improves trabecular outflow rather than creating a new surgical drainage channel.
- 2Discuss variable response, possible transient pressure rise and inflammation, and the possibility that drops or repeat treatment will still be needed.
- 3Follow the treating service's peri-laser pressure checks and review schedule, continuing existing medication unless an explicit change has been prescribed.
02Incisional treatmentChoose surgery for the required pressure goalAdvanced disease, progression or inadequate tolerated treatment makes a stronger pressure-lowering intervention appropriate.+
- 1Discuss augmented trabeculectomy and other suitable surgical options, considering previous surgery, conjunctival scarring, the disease mechanism and the target pressure.
- 2Explain where the fluid will drain, what a bleb or tube does, and the trade-off between pressure control, postoperative interventions and complications.
- 3Agree support for frequent early reviews, provide an exact drop plan and emergency contact route, and preserve baseline records for later assessment of benefit.
03Aftercare and rescueRespond to healing problems or persistent pressurePressure, wound appearance or symptoms suggest incomplete success or a complication after a procedure.+
- 1Assess the eye promptly for infection, leakage, hypotony, scarring, tube obstruction and other causes rather than increasing drops without examining the surgical site.
- 2Arrange surgeon-directed adjustments, which may include changing medicines, releasing or modifying sutures, bleb needling, further laser or another operation.
- 3Continue surveillance of pressure and vision after the immediate problem settles, revisiting the procedure goal and explaining any change in long-term treatment.
05Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- After SLT, the service should check for early pressure elevation according to its protocol and later assess whether the sustained pressure effect meets the agreed goal.
- Filtering surgery requires close early review of wound healing, bleb function, chamber depth and pressure; appointments may lead to active adjustments rather than simple observation.
- Postoperative anti-inflammatory and antimicrobial treatment must follow the named surgeon's regimen, including the intended taper or stop date; these schedules vary with operation and healing response.
- Monitor for later bleb leakage, infection, scarring, tube exposure and ongoing optic nerve progression, and remind the person that urgent symptoms remain relevant years after surgery.
- Check that practical restrictions, transport, medicine supply and help with drops are understood, adapting the aftercare arrangements to the person's needs.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
SLT changes trabecular function
Selective laser trabeculoplasty targets pigmented trabecular cells and induces changes that improve conventional outflow. It requires a suitable visible angle. Its effect can lessen over time; repeat SLT may be considered when an initially useful response wanes, but pressure and visual monitoring continue throughout.
Iridotomy equalises pressure across the iris
A small peripheral iris opening allows aqueous to bypass relative pupil block. It can be central to the care of angle-closure disease, but it does not remove an enlarged lens, reverse all peripheral adhesions or restore damaged trabecular tissue. Residual pressure elevation therefore needs further assessment rather than assuming that a patent opening has cured glaucoma.
Trabeculectomy depends on controlled healing
A guarded opening lets aqueous pass to a subconjunctival filtering area. Excessive scarring can close the route, while excessive drainage can produce hypotony. Mitomycin-C may be used as surgical augmentation to limit scarring; this is an off-label use identified by NICE, and exposure is set by the surgeon rather than a universal ward prescription.
Tube devices redirect the fluid
A drainage tube conveys aqueous to a plate-associated reservoir away from the usual trabecular route. Valved and non-valved devices differ in early flow control. Tube position, blockage, erosion, corneal effects and pressure around the time that flow changes are relevant to follow-up; a tube should not be confused with a tiny angle stent.
Microinvasive procedures are a varied group
Trabecular bypass stents or trabeculotomy seek to improve conventional drainage and are often considered alongside cataract surgery in selected open-angle eyes. Their potential benefit and limitations differ from bleb-forming procedures. Device-specific evidence, anatomy and the pressure target determine suitability; the label microinvasive does not establish equivalent effectiveness for advanced glaucoma.
Cyclodiode reduces fluid production
Transscleral cyclodiode treats the ciliary body to reduce aqueous secretion. It may be useful when other approaches are unsuitable or inadequate and can relieve pressure-related pain. Risks include inflammation, persistent high pressure, hypotony and loss of vision, and repeat treatment may be needed. The planned approach should reflect both visual potential and the need for comfort.
Needling addresses a scarred drainage area
A surgeon may use needling to break down scar tissue around a filtering bleb, sometimes with an antimetabolite. This is a further intervention with its own consent and review requirements. Patients should not massage or manipulate a bleb unless taught a specific postoperative manoeuvre by their eye team.
07Common pitfallsFrequent interpretation and management errors.
- 01
Describing SLT, iridotomy and cyclodiode as though all three create the same drainage opening.
- 02
Requiring failure of every medication before offering a surgical discussion for advanced open-angle glaucoma.
- 03
Assuming the smallest available procedure will achieve any target pressure with the fewest follow-up visits.
- 04
Stopping all glaucoma drops after laser or surgery without checking the operation-specific instructions.
- 05
Treating a late painful red eye after trabeculectomy as routine conjunctivitis without urgent bleb assessment.