01 · Start with the diagnosis
PACS, PAC and PACG are not interchangeable.
The drainage angle sits between the cornea and the iris. Fluid produced inside the eye normally leaves through this angle. When the peripheral iris is too close to the drainage tissue, the angle can become crowded or closed.
Before deciding on treatment, I first establish which stage is present. The terms sound similar, but they describe different findings and different levels of risk.
| Term | What it means |
|---|---|
| Primary angle-closure suspect (PACS) | The angle is narrow enough to be at risk of closure, without raised pressure from angle closure, permanent adhesions or glaucomatous optic-nerve damage. |
| Primary angle closure (PAC) | Angle closure has produced raised eye pressure, permanent adhesions in the angle, or both, but without glaucomatous optic-nerve damage. |
| Primary angle-closure glaucoma (PACG) | Angle-closure disease is accompanied by glaucomatous damage to the optic nerve. |
02 · PACS
Observation and LPI can both be reasonable.
PACS is a risk state rather than established glaucoma. Observation means planned review, with repeat assessment of the angle, eye pressure and any evidence that the condition has changed. LPI reduces the part of the risk caused by pupillary block, but it does not mean that follow-up can stop.
What the prevention trials tell us
The ZAP trial found that LPI reduced progression endpoints in community-screened PACS, but the absolute event rate was low. In the Singapore ANA-LIS trial, an endpoint occurred in 5.0% of LPI-treated eyes and 9.4% of untreated eyes over five years—about 22 eyes treated to prevent one study endpoint.
These endpoints commonly meant a new adhesion in the angle or raised eye pressure. They were not the same as glaucoma-related sight loss. The studies therefore support an individualized decision, not “laser for everyone” or “laser is unnecessary.”
How I frame the decision in practice
If a patient has PACS alone, no intermittent symptoms and can return reliably for review, observation is often reasonable. I would move the discussion more towards LPI when:
- Repeated pupil dilation is likely, such as during diabetic retinal surveillance or uveitis care.
- Symptoms suggest intermittent episodes of angle closure.
- Reliable long-term monitoring would be difficult.
If there are no other signs of disease or progression, I generally review these patients yearly whether they are observed or have already had LPI. The interval may be shorter when the pressure, anatomy, symptoms or other examination findings require it. This approach applies to stable patients who fit the PACS picture—not to established disease or an acute attack.
03 · Laser peripheral iridotomy
LPI creates another pathway for fluid through the iris.
During LPI, a laser makes a small opening near the edge of the iris. This equalises the pressure in front of and behind the iris and relieves pupillary block, allowing the iris to fall away from the drainage angle in many eyes.
LPI does not reverse existing optic-nerve damage. The angle may also remain narrow for anatomical reasons other than pupillary block, and some patients still require pressure-lowering treatment. The angle and pressure therefore need to be reassessed after the procedure.
Possible effects after LPI
LPI is generally safe, but it is not risk-free. Short-lived inflammation, a temporary rise in eye pressure or a small amount of iris bleeding can occur. Some patients notice glare, lines or other light-related symptoms afterwards. These often improve with time, but persistent or troublesome symptoms should be assessed individually by an ophthalmologist.
This is a general overview, not a complete procedure-specific consent discussion.04 · PAC and PACG
Established angle-closure disease usually needs more than surveillance.
Once the condition is PAC or PACG rather than PACS alone, treatment usually needs to relieve the anatomical closure and control eye pressure. This is not always a rigid sequence in which laser must be completed before anything else. LPI and pressure-lowering drops may be used at the same time, with the plan adjusted after the angle and pressure are reassessed.
Where lens extraction enters the discussion
Lens extraction is generally considered when a cataract is present. Removing the lens can improve vision and create more space in the front of the eye, which can help open the drainage angle. The expected visual benefit, refractive target and surgical risk still need to be considered.
The EAGLE trial studied a narrowly selected group without cataract who had newly diagnosed PAC with markedly raised eye pressure or PACG. Initial lens extraction produced slightly lower pressure and reduced the need for later pressure-lowering medication and glaucoma procedures compared with standard care based on LPI and medication.
EAGLE does not mean that every patient with narrow angles should have clear-lens extraction. In selected patients—including some who are relatively young—markedly raised pressure or substantial glaucomatous damage may make earlier lens extraction worth discussing. The decision remains individual and includes lens status, angle anatomy, optic-nerve damage, refractive goals and operative risk.
Acute angle closure
Sudden symptoms need urgent assessment.
This guide concerns non-acute narrow angles and angle-closure disease. Sudden severe eye pain, a red eye, blurred vision or coloured haloes—particularly with headache, nausea or vomiting—can indicate acute angle closure. Seek urgent eye care rather than waiting for a routine appointment.
Common questions
Questions patients often ask about narrow angles.
Does PACS mean that I have glaucoma?
No. PACS means that the drainage angle is narrow enough to be at risk of closure, without the pressure-related changes or optic-nerve damage that define more established disease. It still needs an individual assessment and a follow-up plan.
Does everyone with narrow angles need laser iridotomy?
No. Observation and LPI can both be reasonable for PACS. The balance depends on the examination, symptoms, need for repeated pupil dilation, ability to return for monitoring and the person’s preferences.
If I have had LPI, do I still need follow-up?
Yes. LPI relieves one important mechanism of angle closure but does not remove every anatomical cause, reverse existing glaucoma damage or guarantee that eye pressure will remain controlled.
Are pressure-lowering drops only used after laser has failed?
Not necessarily. In PAC or PACG, treatment often addresses the anatomical closure and the eye pressure at the same time. LPI and pressure-lowering drops may therefore be used concurrently.
Does the EAGLE trial mean that I should have early lens extraction?
No. EAGLE studied a narrowly selected group with newly diagnosed PAC and markedly raised pressure or PACG, without cataract. Its findings should not be applied to every person with PACS, PAC or PACG.