Iridoplasty is a laser procedure that physically opens the angle by applying low-energy argon laser to the peripheral iris, causing thermal contraction of collagen in the iris stroma. It is formally called argon laser peripheral iridoplasty (ALPI).
In 1977, Krasnov first developed a method to lower intraocular pressure using laser energy. Initially, only 90 degrees of the angle was treated, but later Kimbrough improved it to a 360-degree full-circumference method using a gonioscopy lens, establishing the basis of current ALPI.
Laser iridotomy (LPI) is a procedure that creates a hole in the iris to relieve the pressure difference between the anterior and posterior chambers (pupillary block). In contrast, ALPI contracts the iris itself to physically pull it away from the angle. For angle closure due to mechanisms other than pupillary block, LPI is insufficient, and ALPI is chosen 4).
QHow is ALPI different from laser iridotomy (LPI)?
A
LPI is a procedure that creates a small hole in the iris to relieve pupillary block. ALPI does not create a hole; instead, it applies laser to the peripheral iris to contract the iris tissue and widen the angle. It is used when the angle remains narrow after LPI or for closure due to causes other than pupillary block, such as plateau iris.
The main indication for ALPI is a condition where appositional angle closure persists after LPI4)5).
Acute Primary Angle Closure (APAC)
When LPI is difficult due to corneal edema: During an acute attack, corneal edema may prevent visualization for LPI. If at least one quadrant of the peripheral iris is visible, ALPI can be performed safely4).
Faster intraocular pressure reduction than medication: The ALPI group showed significantly lower intraocular pressure at 15 minutes, 30 minutes, and 1 hour compared to the systemic medication group4).
Residual closure after LPI: Used as an additional treatment when appositional closure persists after LPI4).
Plateau Iris Syndrome (PIS)
Narrow angle persists after LPI: In plateau iris syndrome, 54–80% of cases are reported to have persistent angle closure after LPI2).
Long-term angle widening: A retrospective study showed that after a single ALPI procedure, angle widening was maintained in 87% of eyes over a mean follow-up of 79 months1)2).
Also indicated in young patients: ALPI was effective in an 18-year-old patient with plateau iris2).
Nanophthalmos: The axial length is short, and with aging, the relative increase in lens thickness can cause angle closure. ALPI is effective for residual closure after LPI.
Iris/ciliary body cysts: For cysts causing appositional angle closure, ALPI can open the angle.
UGH syndrome: Laser iridoplasty has been reported to treat the uveitis-glaucoma-hyphema syndrome caused by iris chafing from an intraocular lens, by moving the iris away from the lens support2).
It is the gold standard for evaluating the degree of angle opening 1). In plateau iris, a “double hump sign” is characteristically observed on indentation gonioscopy1)2).
It allows direct visualization of the anterior position of the ciliary body. It is useful for confirming the diagnosis of plateau iris2).
In an 18-year-old female with plateau iris, ultrasound biomicroscopy revealed anterior displacement of the ciliary body in both eyes, leading to a definitive diagnosis. 2)
First, check whether a narrow angle persists after laser iridotomy. A “double hump sign” on gonioscopy is characteristic. For definitive diagnosis, confirmation of anterior displacement of the ciliary body by ultrasound biomicroscopy (UBM) is recommended. Anterior segment OCT has lower diagnostic accuracy than UBM and is not a substitute.
Pilocarpine eye drops are used to induce miosis, stretching the iris to improve access to the periphery. To prevent postoperative intraocular pressure spikes, brimonidine or apraclonidine is instilled preoperatively 5).
Irradiate perpendicularly to the peripheral iris through an Abraham lens. If no iris stromal contraction is observed, gradually increase the power. Place 5–6 spots per quadrant at equal intervals, with a total of 20–24 spots around the entire circumference.
Using a gonioscopy lens, irradiate the peripheral iris at a low angle of incidence. A spot size of 300–500 µm and a duration of 0.3–0.5 seconds are considered appropriate. Direct irradiation of the trabecular meshwork must be avoided. The indirect method has the advantage of allowing direct visualization of the angle during the procedure.
In a case of plateau iris in an 18-year-old, using a Pascal solid-state laser (532 nm frequency-doubled Nd:YAG) with a spot size of 400 µm and power of 300 mJ, a total of 48 spots were applied over 360 degrees, achieving good angle widening. 2)
For UGH syndrome, a technique has been reported in which the transillumination defect is marked with conjunctival marking and iridoplasty is performed using a Pascal solid-state laser at 600 mW 3).
Immediately after surgery, brimonidine is instilled. Steroid eye drops such as 1% prednisolone acetate are administered 4 to 6 times daily for a short period. Postoperative intraocular pressure is carefully monitored.
ALPI during an APAC attack significantly lowers intraocular pressure at 15 minutes, 30 minutes, and 1 hour compared to systemic medication 4). However, at 15 months postoperatively, no statistically significant difference in IOP control was observed between the ALPI group and the systemic medication group 4).
In ALPI for plateau iris syndrome, 87% of eyes maintained angle opening after a single treatment with a mean follow-up of 79 months, and filtering surgery was not required 1).
In a 59-year-old female with plateau iris syndrome, IOP in the left eye rose again to 49 mmHg 2 months after bilateral LPI. After argon laser iridoplasty, the anterior chamber deepened, and IOP stabilized at 16 mmHg OD and 13 mmHg OS at 6 months. 1)
Urrets-Zavalia syndrome: A rare complication characterized by fixed dilated pupil unresponsive to miotics. It causes photophobia and cosmetic issues but usually resolves spontaneously within about one year.
Corneal endothelial burn: Can occur when the peripheral iris and cornea are in close proximity. Particular caution is needed in cases with shallow anterior chamber.
Iris necrosis: Rarely reported when coagulation spots are applied densely.
Transient intraocular pressure elevation: A transient increase in intraocular pressure may occur after surgery, and can be prevented with preoperative and postoperative apraclonidine eye drops5).
QHow long does the effect of ALPI last?
A
For ALPI in plateau iris syndrome, a single treatment has been reported to maintain angle opening in 87% of eyes for an average of 79 months (approximately 6.5 years). However, the effect may diminish over the long term, and continued use of miotic agents or additional cataract surgery may be necessary. Regular gonioscopic follow-up is important.
The thermal energy of the laser causes degeneration and contraction of collagen fibers in the peripheral iris stroma. This immediate contraction pulls the iris away from the trabecular meshwork, widening the angle.
Thinning of the iris cross-section at the laser irradiation site contributes to angle widening2). However, since the anterior displacement of the ciliary body itself is not improved, the underlying anatomical abnormality remains in plateau iris.
Traditionally, ALPI was indicated for middle-aged and older patients, but a case has been reported in which iridoplasty using a Pascal solid-state laser was effective for acute angle closure due to plateau iris in an 18-year-old2). It is suggested that plateau iris should be considered in the differential diagnosis even in younger patients, and ALPI should be considered early.
A new technique has been reported in which the transillumination defect is marked with conjunctival marking and localized iridoplasty is performed using an Nd:YAG solid-state laser 3). This reduces contact between the intraocular lens haptic and the iris, and no recurrence of UGH was observed for 7 months. It is noted as an option to consider before invasive procedures such as intraocular lens removal.
The latest consensus statement proposes an alternative treatment algorithm including ALPI, anterior chamber paracentesis, and early phacoemulsification aspiration 4). Compared to conventional management with observation after LPI, it may reduce the risk of progression to chronic angle-closure glaucoma.
Shakoor T, Sadhar BS, Sharma P, et al. Seeing Beyond the Expected: An Uncommon Case of Plateau Iris Syndrome in the Outpatient Setting. Cureus. 2024;16(5):e59575.
Sheth S, Lagrew M, Blake CR. Acute Angle Closure in an 18-Year-Old Due to Plateau Iris. Cureus. 2024;16(5):e60608.
Dhillon B, Duff-Lynes SM, Blake CR. A novel method of using transillumination, conjunctival markings and Pascal solid state laser to treat Uveitis-Glaucoma-Hyphema syndrome. Am J Ophthalmol Case Rep. 2022;25:101296.
Chan PP, et al. Management of Acute Primary Angle Closure Attack: Asia-Pacific Angle-Closure Glaucoma Club Consensus Statement. Asia Pac J Ophthalmol. 2025;14:100223.
日本緑内障学会. 緑内障診療ガイドライン（第5版）. 日眼会誌. 2022;126:85-177.
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