Iridotomia laser: ce este si cand se recomanda?

Laser iridotomy: what is it and when is it recommended?

Iridotomia laser este o procedură minim invazivă utilizată în tratamentul glaucomului și prevenirea atacurilor de glaucom cu unghi închis. Iridotomia laser constă în crearea unei mici deschideri în irisul ochiului cu ajutorul unui laser specializat. Această intervenție permite drenarea adecvată a lichidului intraocular și reduce riscul de acumulare a presiunii intraoculare, care poate afecta nervul optic și vederea. Indicațiile pentru iridotomia laser includ unghi îngust, prevenirea glaucomului cu unghi închis și reducerea riscului de atac de glaucom. Această procedură sigură și eficientă oferă pacienților o opțiune de tratament importantă pentru sănătatea ochilor.

1. What is laser iridotomy?

Peripheral laser iridotomy (also described as "laser iridotomy" or simply called "iridotomy") is a medical procedure that uses a laser device to create a hole in the iris, thereby allowing aqueous humor to pass directly from the posterior chamber to the anterior chamber and , consequently, relieving a pupillary block. It is commonly used to treat a wide range of clinical conditions, including primary angle-closure glaucoma, primary camerular angle closure (narrow angle and no signs of glaucomatous optic neuropathy), eyes suspected of primary angle closure (patients with reversible obstruction) and even eyes with secondary causes of iridocorneal angle closure.

In the mid-1970s, the argon laser became the first to be commonly used to perform non-invasive iridotomy. Although well absorbed by the iris pigment, the argon laser (and the Nd:YAG-KTP laser, which is often referred to as the "argon laser") used for iridotomy was associated with some complications and relatively high failure and subsequent closure rates. Q-switched Nd:YAG laser devices (1064 nm YAG laser) emerged in the 1980s and proved to be effective in light-coloured irises because its mechanism of action was independent of the melanin content of the iris. Moreover, it required much less total energy than pure argon/Nd:YAG-KTP 532 nm laser iridotomy, and achieved a superior single-treatment success rate with lower risk of subsequent closure and was less likely to cause corneal, lens and retinal damage.

2. When is this procedure indicated?

Iridotomia periferică cu laser (LPI) este indicată pentru a preveni sau trata pacienții suspecți de blocaj pupilar relativ prin crearea unei căi alternative pentru fluxul apos. Folosit în principal pentru pacienții cu închidere primară de unghi, poate fi util și în glaucomul secundar cu unghi închis și în gestionarea altor tipuri de glaucom cu bloc pupilar asociat. Unghiul iridocornean trebuie, în toate cazurile, examinat cu atenție după LPI pentru a exclude alte mecanisme ale unui unghi închis care necesită tratament.

- Acute primary angle closure (APAC)
- Contralateral eye in acute primary angle closure
- Suspected primary angle closure, narrow/occlusive angle
- Primary angle closure glaucoma and primary angle closure
- Secondary angle closure with pupillary block
- Flat iris configuration and flat iris syndrome
- Misdirection of aqueous humor, cilio-lenticular block, ciliary block or malignant glaucoma
- Pigment dispersion syndrome (PDS), pigmentary ocular hypertension (POH) and pigmentary glaucoma (PG)
- Congenital abnormalities that may be associated with secondary glaucoma
- Systemic drugs with effects on the iridocorneal angle

3. Contraindications of the procedure

The following contraindications should be managed before performing an IPL:

Ocular middle opacities (e.g., corneal edema, anterior chamber inflammation)
Ochi cu risc ridicat (de exemplu, cameră anterioară îngustă, uveită)
Uncooperative patients

4. Types of lasers for LPI

Iridotomy can be performed using the photodisruptive Q-switched Nd:YAG laser (Nd:YAG) or the photothermal Nd:YAG-KTP 532 nm laser (which is still often called Argon laser) and solid-state laser. The two types of laser can also be used in sequential combination. The laser parameters must be individualised for each patient and adjusted accordingly during the procedure. Regardless of the device used, some authors aim for an iridotomy of at least 200 microns in size and ideally 500 microns in diameter.

5. Contraindications of the procedure

Transient increase in intraocular pressure (IOP)
Bleeding in the anterior chamber (hyphema)
Visual dysphotopias
Progresia cataractei
Closure of iridotomy and the need for repeat IPL

Other complications

A reduction in endothelial cell count after IPL has been reported in the literature. Postoperative inflammation is usually transient and mild, rarely leading to posterior synechiae. Rare complications include sterile hypopyon, macular hole formation, cystoid macular edema and retinal hemorrhages

6. Results of the procedure

Intraocular pressure control
Anatomical improvement
Prevention of acute angle closure crisis
Slowing/Stopping disease progression

IPL is an integral component in the management of primary angle closure (PAC). Although IPL has been available since the 1970s, its role in the treatment algorithm for PAC is still under debate; questions such as who should be treated with an iridotomy and whether iridotomy prevents disease progression continue to be relevant today. After IPL, most subjects with primary angle closure syndrome (PACS) can expect to stop receiving treatment. On the other hand, many PAC and APAC eyes and most eyes with primary angle-closure glaucoma (PACG) need additional treatment to control IOP. LPI has a favorable effect on IOP, especially when synechiae are extensive or there is glaucomatous optic nerve damage.

Factors predictive of increased IOP, or need for further treatment after IPL, were those reflecting more severe disease at baseline, such as higher IOP, higher cup-to-disc ratio and higher synechial closure at presentation. The safety and efficacy of IPL for PAC/PACG has promoted a gradual broadening of the criteria for iridotomy over the past two decades. However, more inclusive criteria have spurred debate on treatment algorithms because we still do not know which eyes will develop glaucomatous lesions despite early manifestations of narrow angles, and offering iridotomy too early would expose healthier patients to complications without clear evidence of benefit. More recently, the role of cataract extraction in the spectrum of CAP disease has continued to fuel debate about the timing of IPL and its indications. In fact, the EAGLE study recommends clear lens extraction as first-line treatment for the subgroup of CAP patients with an IOP above 30 mmHg. Newer and more objective angle imaging devices are expected to help predict the success of laser iridotomy in the future.

In conclusion, LPI increases angle width in all stages of PAC and has a favourable effect on IOP in eyes without extensive angle or disc lesions. Although there is a gradual decrease in angle width in PACS eyes after IPL, additional treatment after IPL in this subgroup is rare. Instead, further treatment after IPL is more likely in PAC, APAC and PACG eyes and should be monitored for IOP increase and progression to glaucoma.

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Articles - 21st November 2022

Laser iridotomy: what is it and when is it recommended?

Laser iridotomy: what is it and when is it recommended?

1. What is laser iridotomy?

2. When is this procedure indicated?

3. Contraindications of the procedure

4. Types of lasers for LPI

5. Contraindications of the procedure

6. Results of the procedure

Primary Ophthalmologist Dr. Yasar Servet

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