Argon Laser Peripheral Iridoplasty

1. Essentials of Glaucoma Therapy
2. Lasers
3. Argon Laser Peripheral Iridoplasty

←Laser Peripheral Iridotomy

Transscleral Cyclophotocoagulation →

Primary authors	Clement C. Y. Tham, FRCS(Glasgow) FCOphth(HK) Dennis S. C. Lam, MD(HK) FRCS(Edin) FRCOphth(UK) FCOphth(HK) Robert Ritch, MD

Argon laser peripheral iridoplasty (ALPI) is a procedure in which long-duration, low-power contraction burns placed circumferentially on the peripheral iris open an appositionally closed anterior chamber drainage angle (Figure 24-1). Iris stromal contraction and compaction mechanically pull open the appositionally closed drainage angle, creating a space where none existed before (Figure 24-2). ALPI is not effective at breaking peripheral anterior synechiae, nor does it replace laser iridotomy in eliminating pupil block.

Indications

ALPI is effective in acute primary angle closure (APAC), acute phacomorphic angle closure (phacomorphic glaucoma), plateau iris syndrome, secondary and malignant glaucomas with a component of appositional angle closure, as an adjunct to facilitate laser trabeculoplasty, and to reduce the chance of angle reclosure after goniosynechialysis (GSL).

ALPI is remarkably effective at breaking attacks of acute angle closure, safely and effectively reducing intraocular pressure (IOP), at a time when more definitive treatment (eg, laser iridotomy or cataract extraction) cannot be performed due to corneal edema, very shallow anterior chamber, and significant ocular inflammation. It can be done prior to any medical treatment of the angle closure, and the days in which acute angle closure was treated with hospitalization and infusions of mannitol, along with prolonged medical therapy, in an attempt to break an attack belong to the past.

Techniques

Figure 24-1. (A) Laser peripheral iridoplasty marks on the peripheral iris.

(B) Burns placed too centrally.

Figure 24-2. (A) Ultra-sound biomicroscopy (UBM) image showing an apposition-ally closed angle in an eye with plateau iris syndrome (S indicates sclera; AC, anterior chamber; I, iris; CB, ciliary body; C, cornea; arrows indicate position of laser application.) (B) After ALPI, the angle is open.

(C) When ALPI is not applied peripherally enough (laser applied at position of dimple in iris), the angle remains appositionally closed.

ALPI is performed using an Abraham iridotomy lens (Ocular Instruments, Inc., Bellevue, Washington) under topical anesthesia. Diode laser is also effective. For brown irides, we start with a laser power of 200 mW (240 mW for lighter irides), 500-µm spot size (can be reduced to 200 µm for lighter irides, if there is no contraction even with a power of 360 mW or more), and 0.5 to 0.7 second duration. ALPI is successful even when corneal edema and a very shallow anterior chamber are present. The laser is aimed at the far periphery of the iris. The aiming beam may have to slightly overlap the sclera at the limbus to reach the far iris periphery. A total of 20 to 24 laser spots over the 360 degrees is sufficient. The laser power should be titrated against the observed iris response. If there is no or insufficient iris contraction, the laser power can be increased in steps of 20 mW. On the contrary, the laser power should be reduced if there is bubble formation, iris charring, pigment release from the iris, or if there is a “pop” sound. The endpoint is visible iris contraction and slight deepening of the anterior chamber at the point of laser application.

IOP should be rechecked 1 hour afterward to exclude an IOP spike. Topical steroid 4 times a day should be prescribed to control post-laser iritis. At a subsequent visit, darkroom gonioscopy should be repeated, and further iridoplasty should be added if there are still areas of appositional angle closure.

Precautions

Irreversible iris changes indicate too much power and should be ­avoided . Radial iris vessels, if visible, should be avoided. Iris necrosis or atrophy may occur if too many laser spots are placed too closely together.

Conclusion

Laser peripheral iridoplasty is a safe and effective technique for mechanically opening appositionally closed drainage angles and in situations in which the closed angle results in significant ocular hypertension, and definitive treatments, such as laser iridotomy, cannot be safely performed.

Key Points

1. Laser peripheral iridoplasty mechanically pulls open appositionally closed drainage angles and is effective in breaking acute attacks of angle closure.
2. Laser peripheral iridoplasty is not effective in synechial angle closure and does not replace laser iridotomy in eliminating pupil block.
3. Laser peripheral iridoplasty is useful in APAC, phacomorphic glaucoma, plateau iris syndrome, secondary and malignant glaucomas with a component of appositional angle closure, as an adjunct to facilitate laser trabeculoplasty, and as an adjunct to reduce the chance of angle reclosure after GSL.
4. Laser peripheral iridoplasty can be safely performed even in situations in which laser iridotomy is not safe due to corneal edema and/or very shallow anterior chamber.
5. When performing laser peripheral iridoplasty, we are aiming for just iris stromal contraction. Bubble formation, iris charring, pigment release from the iris, or a “pop” sound signify too much power and should be avoided.