YAG peripheral iridotomy

A YAG peripheral iridotomy is a laser treatment used to prevent angle closure glaucoma. It takes a minute or two per eye and is done in the outpatient clinic.

Urgent: sudden severe eye pain with blurred vision, haloes around lights, a red eye, headache and feeling sick are signs of an acute angle closure attack. Sight can be lost within hours. Go to an emergency department the same day.

These are the questions people ask about it in clinic.

Why do I need this? My eyes feel fine

That is exactly the point — this is done before anything goes wrong.

Fluid inside the eye is made behind the iris and has to travel forward through the pupil to drain away at the angle where the iris meets the cornea. In some eyes that angle is naturally narrow. Long-sighted eyes are smaller and more crowded inside, and the lens thickens gradually throughout life, pushing the iris further forward.

If the pupil then widens — in dim light, in the cinema, or with certain medicines — the iris can bunch up and block the angle completely. Drainage stops, the pressure climbs fast, and that is an acute attack.

The laser makes a tiny opening in the outer edge of the iris, usually tucked under the upper eyelid. Fluid can then pass straight through without going via the pupil, so the iris falls back and the angle stays open.

How do you know my angle is narrow if I have no symptoms?

By looking directly at it. A mirrored contact lens is placed on the eye — this is called gonioscopy — which lets the drainage angle be examined properly.

It cannot be judged from the outside of the eye, and a normal pressure reading does not rule it out. That is why people with narrow angles and perfectly normal pressures are still advised to have the treatment.

Will it hurt?

Not much. Anaesthetic drops numb the eye first.

You will hear sharp clicks and see bright flashes. Most people describe a brief pinprick or a dull ache. It is over quickly — roughly one to two minutes per eye.

What happens on the day?

Before. Take your usual medicines and eat normally. A drop is used to make the pupil small, which stretches the iris thin and makes the opening easier to create. This can give you a dull ache in the brow and dim your vision for a few hours. You will usually be given a pressure-lowering drop as well.

During. Anaesthetic drops, then a contact lens with gel to focus the laser. You sit at a machine much like the one used for a routine eye examination.

After. Blurred vision for a few hours. The eye may ache mildly and look red for a day or two. You will be given anti-inflammatory drops for about a week, and your pressure is checked around an hour afterwards.

Can I drive home?

No, not on the day. The drop used to shrink the pupil dims your vision and makes focusing difficult, and it is worse in low light. Please arrange a lift.

You can usually drive normally the next day.

Will my vision be better afterwards?

No, and this is worth being clear about. The treatment is preventive. It stops the angle closing; it does not sharpen your sight or reverse damage that has already happened.

Do both eyes need doing?

Usually yes. The two eyes are almost always built the same way, so if one is at risk the other very likely is too. After an attack in one eye, treating the second is standard.

I've noticed a line of light since the laser

A small number of people see a streak, arc or ghost image, usually in bright conditions, if the opening is not quite covered by the eyelid.

It nearly always settles or stops being noticeable within a few weeks. Mention it if it persists.

Is that it, or do I need to keep coming back?

You will still be followed up.

If the angle had already caused damage, you have angle closure glaucoma and it is monitored like any other glaucoma. Even where the laser was purely preventive, the angles are rechecked, because the opening can occasionally close over — uncommon, but easily re-treated if it happens.

My tablet leaflet says "do not use if you have glaucoma"

This is a very common worry and usually an unnecessary one.

That warning refers to angle closure glaucoma, not the ordinary open angle kind. Before treatment, some medicines can trigger an attack by widening the pupil — certain antidepressants, antihistamines, and medicines for bladder problems or motion sickness.

Once you have had a working iridotomy in both eyes, that risk is largely removed.

Please ask rather than stopping any medicine on your own.

Should my family be checked?

Yes. Narrow angles depend on the shape of the eye and run strongly in families.

Close relatives should have their angles assessed. It is one of the few situations in eye medicine where a simple examination genuinely prevents blindness.

Next steps

Patients — contact the clinic to arrange an appointment.

GPs and optometrists — refer directly to Limerick or Ennis, including by Healthmail.