Glaucoma lasers and surgery: from iridotomy to tube shunts
- Topic
When drops are not enough, laser or surgery lowers eye pressure. After glaucoma surgery, a red, sticky eye can mean bleb infection: refer the same day.
See it in 3D: Drainage angle · Iris · Ciliary body
What it is
Every glaucoma treatment lowers intraocular pressure. Laser peripheral iridotomy opens a small hole in the peripheral iris so aqueous bypasses the pupil, treating and preventing angle closure. Selective laser trabeculoplasty improves outflow through the trabecular meshwork in open-angle glaucoma. Trabeculectomy creates a guarded channel that drains aqueous under the conjunctiva into a bleb; tube shunts carry aqueous to a plate behind the eye; minimally invasive glaucoma surgery (MIGS) uses tiny devices or incisions; cyclodestruction reduces aqueous production.
Key facts
- Iridotomy: after an acute angle-closure attack (once the pressure is lowered), in the fellow eye, and in narrow angles at risk of closing.
- Selective laser trabeculoplasty: open-angle glaucoma and ocular hypertension; a valid first-line alternative to drops; the effect fades over years and it can be repeated.
- Trabeculectomy: antifibrotic agents (mitomycin C or fluorouracil) are applied to stop scarring; the bleb sits under the upper lid.
- Tube shunts: after failed trabeculectomy, and in neovascular, uveitic or complex glaucoma; risks include tube exposure and loss of corneal endothelium.
- MIGS: often combined with cataract surgery in mild to moderate glaucoma; safer but with a smaller pressure drop.
- Cyclodestruction (diode laser to the ciliary body): refractory glaucoma or blind, painful eyes; risks are inflammation and very low pressure (hypotony).
In clinical practice
- A bleb can become infected months or years after surgery: red eye, discharge, a milky white bleb, pain and blurred vision; it can progress to endophthalmitis within hours.
- Pressure that is too low after surgery (hypotony) blurs vision through choroidal folds, effusions or macular folds.
- Rubbing the eye and wearing contact lenses over a bleb raise the risk of infection and leakage.
- A 'conjunctivitis' in an eye with a bleb or tube is never treated as routine pink eye.
Next step / Initial management
- Red eye, discharge or pain in an eye with a trabeculectomy bleb or a tube: same-day ophthalmology (bleb infection or endophthalmitis).
- Acute angle closure: lower the pressure first, then ophthalmology performs iridotomy in both eyes.
- Glaucoma that progresses on drops, or a patient who cannot use or tolerate drops: refer to discuss laser or surgery.
- After surgery, follow the drop plan given by ophthalmology; glaucoma drops in the operated eye are often stopped, those in the other eye are not.
- Sudden loss of vision or severe pain after glaucoma surgery: same-day review.
Test yourself
Think of the answer, then tap the question to see it.
What does laser peripheral iridotomy do, and when is it used?
It opens a hole in the peripheral iris so aqueous bypasses pupillary block; it is used in angle closure, in the fellow eye and in narrow angles at risk.
Which drug is applied during trabeculectomy to reduce scarring of the bleb?
Mitomycin C (or fluorouracil).
Years after a trabeculectomy, a patient has a red, discharging eye with a milky bleb. What is it and what is the next step?
A bleb-related infection that can progress to endophthalmitis; same-day ophthalmology.
Which glaucoma procedure lowers pressure by reducing aqueous production rather than improving outflow?
Cyclodestruction of the ciliary body, usually with a diode laser.
Connections
See it in 3D3
The structures of Durgical's 3D anatomy where it is found.
In Pharmacology3
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Laser Trabeculoplasty (StatPearls Publishing (NCBI Bookshelf), 2023); Minimally Invasive Glaucoma Surgery (StatPearls Publishing (NCBI Bookshelf), 2023); Cyclodiode Laser Glaucoma Therapy (StatPearls Publishing (NCBI Bookshelf), 2022); Trabeculectomy (EyeWiki (American Academy of Ophthalmology), 2025); Laser Peripheral Iridotomy (EyeWiki (American Academy of Ophthalmology), 2025); Glaucoma Drainage Devices (EyeWiki (American Academy of Ophthalmology), 2025).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.