LPI stands for laser peripheral iridotomy, a quick in-office laser procedure that creates a tiny hole in the colored part of your eye (the iris) to improve fluid drainage and prevent or treat a dangerous rise in eye pressure. It is one of the most commonly performed laser procedures in ophthalmology and is primarily used to manage narrow-angle glaucoma and related conditions.
How LPI Works
Your eye constantly produces a watery fluid called aqueous humor that flows from behind the iris, through the pupil, and out through a drainage channel in the front of the eye. In some people, the iris sits too close to the lens, creating a blockage at the pupil that traps fluid behind the iris. This trapped fluid pushes the iris forward, narrowing or closing the drainage angle and causing eye pressure to climb. Left untreated, the resulting spike in pressure can damage the optic nerve and threaten vision.
LPI solves this by using a laser to punch a small opening in the outer edge of the iris. That hole acts as a bypass, letting fluid flow directly from behind the iris into the front chamber without needing to squeeze past the pupil. Once the pressure equalizes on both sides of the iris, the iris flattens back into a normal position and the drainage angle reopens. In roughly two-thirds of patients, this widening of the angle is sustained over the long term.
Who Needs an LPI
Ophthalmologists have traditionally treated narrow angles preventively with LPI rather than waiting for an acute attack. The procedure is most often recommended for three overlapping groups:
- Primary angle-closure suspects: People whose iris contacts the drainage meshwork across a significant portion of the eye, even though their pressure is still normal and the optic nerve looks healthy. These patients haven’t had an attack yet, but their anatomy puts them at risk.
- Primary angle closure: People who already show elevated pressure or adhesions (scar tissue sticking the iris to the drainage angle) but don’t yet have optic nerve damage.
- Acute angle-closure attacks: A sudden, painful spike in eye pressure that requires urgent treatment. LPI is typically performed once the acute episode is brought under control with medications, and is also done in the other eye to prevent a future attack there.
During a gonioscopy exam, your doctor uses a mirrored lens to directly view the drainage angle. Angles are graded on a scale where Grade 2 (about 20 degrees) is considered narrow and Grade 1 (10 degrees or less) is extremely narrow. A grade of zero means the angle is closed. These measurements, combined with your pressure readings and optic nerve appearance, determine whether LPI is appropriate.
What Happens During the Procedure
LPI is performed in the office and typically takes only a few minutes per eye. Before the laser is applied, your doctor instills eye drops that constrict the pupil. This pulls the iris taut and makes it thinner, which helps the laser penetrate more easily. Research confirms that these drops significantly reduce iris thickness, creating a better target for the laser beam. A numbing drop is also applied so you won’t feel pain.
You sit at a machine similar to the one used for routine eye exams. A small contact lens is placed on your eye to focus the laser and keep you from blinking. The doctor then fires short bursts from a laser, most commonly an Nd:YAG laser, at the outer edge of the iris until a tiny hole opens. You may see a bright flash and feel a mild pinch or nothing at all. The entire process is usually over in under five minutes.
Recovery and What to Expect Afterward
Recovery from LPI is straightforward compared to surgical glaucoma procedures. Most people notice mild soreness, light sensitivity, or slight blurriness for a few hours. Your doctor will typically prescribe anti-inflammatory eye drops to use for several days to a week to control any swelling. A follow-up visit is usually scheduled within one to two weeks to check your eye pressure and confirm the opening is functioning properly.
There are no major activity restrictions. Most people return to normal routines the same day or the next day, though you may want to arrange a ride home since your vision can be slightly blurry from the drops and the contact lens used during the procedure.
Pressure Spikes After LPI
The most common short-term concern is a temporary jump in eye pressure. About 10% of treated eyes experience a pressure spike of 8 mmHg or more within the first hour. This usually resolves on its own, which is why your doctor checks your pressure before you leave the office. By two weeks, fewer than 1% of eyes still show an elevated reading. Only about 0.5% of eyes spike high enough to need additional medication to bring the pressure down.
Visual Side Effects
A small percentage of people notice subtle visual disturbances after LPI. A systematic review of the evidence found that about 2 to 3% of patients experience linear dysphotopsia, a perception of faint lines in their vision, regardless of where the hole is placed. Ghost images occur in roughly 5% of patients, while shadows affect 2 to 3%. Interestingly, halos and glare, which many people worry about, actually tend to decrease after LPI, likely because the procedure stabilizes the iris and improves the overall optics of the eye.
These visual symptoms are more noticeable in bright lighting conditions and, for most people, either fade over time or become easy to ignore. Placement of the iridotomy under the upper eyelid (the standard approach) helps minimize these effects since the lid covers the opening during normal gaze.
How Effective Is LPI Long Term
A landmark 14-year study from China tracked over a thousand eyes that were at risk for angle closure. Eyes treated with LPI were about 69% less likely to progress to primary angle closure compared to untreated eyes. Only one LPI-treated eye developed an acute angle-closure attack over the entire follow-up period, compared to five in the untreated group. That said, the overall risk of progression was relatively low even in untreated eyes, which is why the decision to treat is based on individual risk factors rather than a blanket recommendation for every narrow angle.
One limitation is that LPI doesn’t work perfectly for everyone. Long-term follow-up data show that about one-third of treated eyes still have some degree of persistent angle narrowing on examination, even though the iridotomy is open. In these cases, the underlying anatomy, often a thick iris or a large lens pushing everything forward, contributes to ongoing crowding that a small hole alone can’t fully resolve.
LPI vs. Lens Removal
For patients with more advanced angle closure or angle-closure glaucoma, removing the eye’s natural lens and replacing it with a thin artificial one (essentially the same surgery as cataract removal) is an increasingly popular alternative. The EAGLE study, a major trial funded by the UK’s Medical Research Council involving 419 patients, compared lens extraction directly against LPI as a first-line treatment. Lens removal proved superior for both pressure control and patient-reported quality of life. Patients in the lens removal group needed fewer medications and fewer additional surgeries over time, while quality of life scores in the LPI group actually declined over the follow-up period.
Despite the more invasive nature of lens surgery, the complication rate was actually lower in the surgical group (25 patients with at least one complication) than in the LPI group (50 patients). This doesn’t mean LPI is a poor choice. For early-stage angle-closure suspects with healthy lenses and normal pressure, LPI remains a sensible, minimally invasive first step. Lens extraction tends to be reserved for patients who have already developed elevated pressure, optic nerve damage, or a visually significant cataract.