LPI is indicated in gonioscopically-proven occludable angles after an AAC episode as 50% of patients will suffer a second attack in the fellow eye over a 5-year period. The fellow eye of a patient with AAC crisis should be evaluated because it is at high risk for a similar event and can occur within days of the first episode. Contralateral Eye in Acute Primary Angle Closure In conclusion, LPI associated with medical treatment is the preferred definitive treatment of acute angle-closure glaucoma with a pupillary block mechanism. īefore performing an LPI, however, patients experiencing APAC should receive aqueous suppressants to lower the IOP, relieve symptoms, improve cooperation and visualization of the ocular media in order to safely and effectively apply the laser beam. It is essential to perform LPI in the fellow eye when indicated. The technique is usually performed soon after the diagnosis is made in order to prevent irreversible vision loss and prevent a recurrent AAC episode. The benefit of LPI is well established to treat and prevent an acute angle closure (AAC) crisis.
The indications for LPI are summarized in table 1. The iridocorneal angle should be, in all cases, carefully examined after LPI to rule out other mechanisms of a closed angle requiring treatment. Mainly used for patients in the primary angle closure spectrum, it can also be useful in secondary angle closure glaucoma and in the management of other types of glaucoma with associated pupillary block. Laser peripheral iridotomy (LPI) is indicated to prevent or overcome a suspected relative pupillary block by creating an alternative pathway for aqueous flow. Furthermore, it required considerably less total energy than pure argon/Nd:YAG-KTP 532 nm laser iridotomy, achieved a superior rate of single treatment success with lower risk of subsequent closure and was less likely to cause damage to the cornea, lens and retina. Q-switched Nd:YAG laser (YAG laser 1064 nm) devices surfaced in the 1980’s and demonstrated to be effective in light-coloured irides because its mechanism of action was independent of the melanin content of the iris. Although it is well absorbed by iris pigment, argon laser (and Nd:YAG-KTP laser, which is often referred to as "argon laser") iridotomy alone was associated with some complications and relatively high failure and subsequent closure rates. In the mid-1970’s, argon laser became the first to be routinely used to perform a non-invasive iridotomy. However, since the emergence of laser technology in the field of ophthalmology, laser peripheral iridotomy (LPI) has largely surpassed the former technique. The first report of an effective surgical treatment for glaucoma was made in 1857 by the German ophthalmologist Albrecht von Graefe, who described the execution of a broad-sector surgical iridectomy through a corneal wound. It is commonly used to treat a wide range of clinical conditions, encompassing primary angle‐closure glaucoma, primary angle closure (narrow angles and no signs of glaucomatous optic neuropathy), patients who are primary angle‐closure suspects (patients with reversible obstruction) and even eyes with secondary causes of iridocorneal angle-closure. Laser peripheral iridotomy (also described as ‘laser iridotomy’ or simply termed 'iridotomy') is a medical procedure which uses a laser device to create a hole in the iris, thereby allowing aqueous humor to traverse directly from the posterior to the anterior chamber and, consequently, relieve a pupillary block.
Credits: Professor Ana IM Miguel, Polyclinique de la Baie, France. Slit lamp photo of a superior iridotomy at 10 o'clock. Iridotomy closure and necessity for repeat LPI
5.1 Argon/Nd:YAG-KTP 532 nm or solid-state Laser.Systemic drugs with effects on the iridocorneal angle Congenital anomalies that can be associated with secondary glaucoma Aqueous Misdirection, Cilio-lenticular block, Ciliary Block or Malignant Glaucoma Plateau Iris Configuration and Plateau Iris Syndrome Pigmentary Dispersion Syndrome (PDS), Pigmentary Ocular Hypertension (POH) and Pigmentary Glaucoma (PG) Primary Angle Closure (PAC) and Primary Angle-Closure Glaucoma (PACG) Primary-Angle Closure suspect (PACS), “narrow” or “occludable” angle