Glaucoma · Patient & Surgeon Series
Most glaucoma is silent.
This kind can arrive
overnight.
In angle-closure glaucoma the iris physically shuts the eye's drain. Sometimes slowly, sometimes in a single evening, with pain, halos and vomiting. Here is the anatomy behind it, the symptoms that mean go now, and what two randomised trials showed about laser iridotomy and lens extraction.
are angle-closure
to injure the nerve
ZAP & EAGLE
Section 01 — The Mechanism
Same disease name.
A completely different
plumbing problem.
Aqueous humour is made behind the iris, flows forward through the pupil, and leaves the eye through the trabecular meshwork in the drainage angle — the narrow gutter where the iris root meets the inside of the cornea. Glaucoma is optic nerve damage, usually driven by pressure. What differs between types is where the outflow fails.
In open-angle glaucoma, the angle is wide open on examination but the meshwork itself drains poorly. In angle-closure disease, the meshwork may be perfectly healthy — it is simply covered. The peripheral iris has been pushed forward against it, either intermittently or permanently, and fluid cannot reach the drain at all.
The commonest mechanism is pupillary block. In a small, crowded front chamber, the back of the iris rests firmly on the front of the eye's natural lens. Aqueous struggles to pass through the pupil, pressure builds behind the iris, and the thin peripheral iris bows forward like a sail — until it touches the meshwork and seals the angle. The lens matters enormously here: it keeps growing thicker throughout life, steadily moving the iris forward. That is why angle closure is mostly a disease of people over 50, and why removing the lens can cure the anatomy.
Angle-closure glaucoma happens when the iris is pushed against the eye's drainage meshwork and blocks it. Usually the cause is pupillary block: in a short, crowded eye the iris rests on an ageing, thickening natural lens, fluid is trapped behind it, and the peripheral iris bows forward to close the angle. It can be silent and gradual, or sudden — an acute attack with pain, red eye, halos and vomiting that needs emergency treatment. Treatment aims to reopen the angle, not just lower pressure: a laser peripheral iridotomy bypasses the block, and replacing the lens with a thin intraocular lens deepens the chamber. Glaucoma drops and surgery handle any damage already done.
Section 02 — Interactive
Watch the lens
close the angle.
This cross-section shows the front of a short, crowded eye. Thicken the natural lens and watch it push the iris forward and narrow the drainage angle. Then swap it for a thin intraocular lens and see why lens extraction is now a first-line option for many patients.
The model exaggerates for clarity, but the direction is real. Anterior chamber depth and lens thickness are among the strongest anatomical predictors of angle closure, and a modern intraocular lens is a fraction of the thickness of the crystalline lens it replaces. After lens extraction the iris falls back, the chamber deepens and the angle widens in most eyes — which is the anatomical logic the EAGLE trial set out to test.
Section 03 — The Acute Attack
The symptoms that mean
go to an eye emergency now.
An acute attack happens when the angle closes all the way round, suddenly. Pressure that is normally in the low-to-mid teens (mmHg) can climb to several times that within hours. The cornea swells, the nerve is compressed, and the eye hurts.
Typical features are a severe, deep ache in one eye or brow, a red eye, blurred or foggy vision, rainbow-coloured halos around lights, headache, and nausea or vomiting. The pupil is often mid-dilated and reacts poorly, and the eye can feel hard. Because headache and vomiting can overshadow the eye, attacks are sometimes first treated as migraine or gastroenteritis — a costly delay.
Attacks often start in dim light (a cinema, an evening at home) or after something that widens the pupil: dilating eye drops, some cold and allergy remedies, anticholinergic medicines, or stress. A separate drug-induced form is caused by topiramate and related sulfonamide medicines, which swell the ciliary body and push the lens-iris diaphragm forward — usually in both eyes, usually within the first weeks of starting the drug. That form is managed differently, so the medicine history matters.
In the emergency department the aim is to bring pressure down fast and then break the block. That usually means pressure-lowering drops, oral or intravenous acetazolamide, sometimes an intravenous hyperosmotic agent, and pilocarpine once pressure has fallen enough for the iris to respond. Definitive treatment — a laser iridotomy, or in some cases lens extraction — follows once the cornea clears. Because the other eye usually shares the same anatomy, it is normally treated preventively too.
Section 04 — Risk & Diagnosis
Who has narrow angles,
and how they are
actually found.
The risk profile is anatomical first: short eyes, shallow chambers and thick lenses. That translates into a recognisable group of people — and a disease that is far commoner in Asia than in Europe.
Recognised risk factors include age over 50, long-sightedness (hyperopia, which usually means a shorter eye), female sex, a family history of angle closure, and East Asian or South Asian ancestry. Global modelling by Tham and colleagues estimated about 20 million people living with primary angle-closure glaucoma in 2013 — roughly three in ten of all glaucoma cases — with the large majority in Asia, and angle closure accounts for a disproportionate share of glaucoma blindness relative to its numbers.
The international ISGEO classification, set out by Foster and colleagues, separates three stages that sound similar but are managed differently:
A routine eye pressure check alone will miss many narrow angles, because pressure can be normal between episodes. If you are hyperopic, over 50, of Asian ancestry, or have a relative with angle closure, it is reasonable to ask specifically whether your angles have been examined.
Section 05 — The Evidence
Two trials that changed
how the angle is opened.
For decades the default for any narrow angle was a laser iridotomy. Two large randomised trials refined that: one questioned treating everyone with narrow angles; the other made lens extraction a first-line option for established disease.
ZAP (Zhongshan Angle Closure Prevention trial). He and colleagues randomised one eye of each of 889 Chinese adults aged 50–70 with bilateral primary angle-closure suspect to laser iridotomy, leaving the other eye as an untreated control. Over six years, treated eyes reached the endpoint (raised pressure, adhesions or an acute attack) about half as often as untreated eyes. But the event rate in untreated eyes was low, and the authors concluded that the benefit was too modest to justify routine prophylactic iridotomy across this population. The practical result: for suspects, treatment is an individual judgement weighing anatomy, symptoms, access to follow-up and drug exposure.
EAGLE (Effectiveness in Angle-closure Glaucoma of Lens Extraction). Azuara-Blanco and colleagues randomised 419 people aged 50 or over with newly diagnosed primary angle closure with pressure of 30 mmHg or more, or primary angle-closure glaucoma, to clear lens extraction or to laser iridotomy plus standard care. At three years, the lens extraction group had better patient-reported quality of life, slightly lower pressure, needed fewer glaucoma medicines and fewer further operations, and the strategy was judged cost-effective. The authors suggested clear lens extraction be considered as a first-line option for this group.
Illustrative visualisation of the direction and rough magnitude of findings reported by the ZAP (He et al., 2019) and EAGLE (Azuara-Blanco et al., 2016) trials — bar lengths are not data values. See References for the source papers.
in ZAP
in EAGLE
(2013 estimate)
Neither trial says lens extraction suits everyone. EAGLE enrolled people with clear lenses who were at least 50, with established or high-pressure disease, operated on by experienced surgeons. Removing a clear lens in a younger eye costs natural focusing ability, and surgery in a very shallow chamber is technically demanding. What the evidence changed is the default conversation: for the right patient, the lens is not a bystander but the treatment target.
Section 06 — Treatment Ladder
Open the angle first.
Then treat
whatever damage remains.
Management follows stage and mechanism. The guiding idea is to fix the anatomy where possible, rather than only chase pressure with drops.
Laser peripheral iridotomy (LPI). A laser makes a tiny opening in the peripheral iris so aqueous can bypass the pupil. The bowed iris flattens and the angle often widens. It is quick and done in clinic, but it does not help plateau iris or a lens-dominated angle much, and some eyes still need more treatment later. Mild glare or a faint line in vision is a recognised side effect in a minority.
Lens extraction. Removing the natural lens — whether cloudy (cataract surgery) or clear — and implanting a thin intraocular lens deepens the chamber far more than an iridotomy can. It also corrects the cataract that many angle-closure patients already have. In crowded eyes it is a demanding operation: little working space, a cornea close to the instruments, and sometimes weak zonules.
Medicines and glaucoma surgery. Drops lower pressure in eyes where the angle is open but drainage is still damaged, or where adhesions have scarred part of the angle shut. If pressure remains uncontrolled, trabeculectomy, tube surgery or goniosynechialysis combined with lens extraction may be considered. Laser iridoplasty is an option for some plateau-iris configurations.
Section 07 — For Surgeons & Distributors
Lens extraction in a
crowded eye: what the tray needs.
When lens extraction is the angle-closure treatment, the operation is a cataract procedure performed in some of the shallowest chambers a surgeon will meet. Consumable choice is not cosmetic in these eyes.
Shallow chambers bring instruments and lens fragments close to the corneal endothelium, so viscoelastic strategy matters: many surgeons favour a dispersive OVD layer to coat the endothelium and a cohesive OVD to create and hold space. A foldable posterior chamber IOL placed in the bag provides the thin optic that deepens the chamber. Agaaz supplies this category — including PURE-HYAL sodium hyaluronate and OP-VISC HPMC viscoelastics and foldable IOLs such as OP-VIEW AS — to surgeons and distributors. The choice of device and technique for a given eye remains the operating surgeon's.
For the rheology behind dispersive versus cohesive choices, see our guide to cohesive vs dispersive OVDs in Related guides below.
Section 08 — FAQ
Frequently asked questions
about angle-closure glaucoma.
A sudden, severe ache in or around one eye, a red eye, blurred or misty vision, coloured halos around lights, headache, and often nausea or vomiting. The pupil may look mid-dilated and sluggish and the cornea hazy. Because the nausea and headache can dominate, attacks are sometimes mistaken for migraine or a stomach upset. It is an emergency: eye pressure can rise high enough to damage the optic nerve within hours.
In open-angle glaucoma the drainage angle is physically open but the trabecular meshwork drains poorly, so pressure rises slowly and painlessly. In angle-closure glaucoma the iris is pushed against the drainage meshwork and physically blocks it. That can happen gradually and silently (chronic angle closure) or abruptly (an acute attack). The distinction matters because angle closure is treated by opening the angle — with a laser iridotomy or by removing the eye's natural lens — rather than with drops alone.
Often, if narrow angles are found before damage occurs. Gonioscopy or anterior segment OCT can show an angle at risk, and a laser peripheral iridotomy can relieve pupillary block. The ZAP trial found iridotomy roughly halved the risk of progression in people with narrow angles but no glaucoma, although the absolute risk without treatment was low, so the decision is individual. People told they have narrow angles should also avoid unsupervised use of drugs that dilate the pupil.
Yes, for selected patients. The natural lens thickens with age and pushes the iris forward; replacing it with a much thinner intraocular lens deepens the chamber and opens the angle. The EAGLE randomised trial found that, in people aged 50 or over with primary angle-closure glaucoma or high-pressure primary angle closure, clear lens extraction gave better quality of life, slightly lower pressure, fewer glaucoma drops and better cost-effectiveness at three years than laser iridotomy with standard care.
Drugs that dilate the pupil can precipitate an attack in an eye with anatomically narrow angles — including dilating eye drops, some anticholinergic and antihistamine medicines, certain decongestants and some antidepressants. Topiramate and related sulfonamide drugs can cause a different, usually bilateral, angle closure by making the ciliary body swell, typically within the first weeks of starting. Anyone told they have narrow angles should mention it to every prescriber and pharmacist.
Yes. The two eyes usually share the same crowded anatomy, and untreated fellow eyes have historically had a high risk of their own attack in the following years. For that reason a preventive laser iridotomy is generally recommended in the fellow eye after an acute attack, once the affected eye is stabilised.
Section 09 — References
Peer-reviewed
citations.
Section 10 — Keep Reading
Related guides
from Beyond Vision.
Start writing here...
Angle-Closure Glaucoma: Acute Attack Symptoms, Laser Iridotomy & Why Lens Extraction Can Open the Angle (2026 Guide)