Peripheral Iridotomy for Narrow Angles — Treatment in Miranda

Peripheral iridotomy (PI) is a YAG laser procedure used to treat narrow anterior chamber angles and to reduce the risk of angle-closure glaucoma. It is performed in the consulting rooms at Miranda and is most often offered preventively, in eyes identified as anatomically at risk before any symptoms have developed.

Narrow Angles and Angle Closure

The anterior chamber is the front part of the eye, between the cornea and the iris. Fluid (aqueous) is constantly produced inside the eye and drains out through a structure at the angle where the iris meets the cornea. In some eyes — typically smaller eyes, longer-sighted eyes, and certain ethnic groups — this drainage angle is narrower than average.

When the angle is narrow, the iris can intermittently or completely block the outflow of aqueous, causing eye pressure to rise. This is called angle closure, and it can occur:

• Acutely — a sudden, painful, sight-threatening rise in eye pressure with red eye, blurred vision, halos around lights, headache, and nausea
• Subacutely — episodes of mild brow ache or halos that come and go
• Chronically — slow, painless damage to the optic nerve over years (a form of glaucoma)

Most patients with narrow angles never know they are at risk until it is identified at an eye examination.

How Narrow Angles Are Identified

Narrow angles are typically identified at routine examination using gonioscopy — a slit-lamp technique that uses a contact lens to view the drainage angle directly. At Eye Surgeons Miranda, the Pentacam is the most valuable imaging tool for this assessment — a non-contact scan that maps the anterior chamber depth and angle in three dimensions. OCT of the anterior segment is also sometimes used.

Where the angle is found to be at risk, peripheral iridotomy is generally recommended before angle closure occurs.

The Procedure

Peripheral iridotomy uses the YAG laser to create a small opening in the periphery of the iris. The opening allows aqueous fluid to bypass any block at the angle and reach the drainage structures freely, reducing the risk of pressure spikes and chronic angle damage.

What to expect on the day

• Anaesthetic drops are placed on the surface of the eye
• A drop is given that constricts the pupil — making the iris easier to treat
• A contact lens is placed on the eye to focus the laser
• A small number of laser pulses create the opening — patients typically describe a few brief clicks; the procedure is not painful
• An eye-pressure check is performed before going home

The opening is small and is usually placed under the upper lid where it is not visible. Both eyes are commonly treated, on the same day or in separate visits.

After the Procedure

• Vision is unchanged in most cases — the procedure is preventive, not corrective
• An anti-inflammatory drop is prescribed for a short period
• An eye-pressure check is arranged for the following week

Once a peripheral iridotomy has been performed and is functioning, the immediate risk of angle closure in that eye is greatly reduced. Long-term review remains important, however, as some patients can develop other forms of glaucoma over time.

Risks

Peripheral iridotomy has a long-established safety record. Short-term effects can include a brief rise in eye pressure, mild inflammation, or a temporary feeling of glare from the new opening. Less commonly, the iridotomy can close over time and need a repeat treatment. These risks are discussed at the assessment before the procedure is recommended.