Glaucoma is the most common cause of irreversible blindness in the world. The management of glaucoma by laser procedures has become one of the useful modalities, but the controversy that has arisen lately is in determining the appropriate patient candidates for laser iridotomy. The most frequently performed procedure is laser peripheral iridotomy (Laser Peripheral Iridotomy / LPI).

As many as 60.5 million people suffer from primary glaucoma, globally in 2010. This number continues to increase to 64.3 million sufferers in the population aged 40-80 years in 2013 and is predicted to continue to increase until it reaches 76 million sufferers by 2020.

Primary angle-closure glaucoma (PACG) has a worse prognosis than open-angle glaucoma. Blindness rates were higher in closed-angle glaucoma, and the prevalence of closed-angle glaucoma is highest in the Asian continent. However, blindness due to closed-angle glaucoma tends to be more preventable than open-angle glaucoma if it is appropriately managed early on. These facts have implications for the need for attention to closed-angle glaucoma, especially in preventing glaucoma in at-risk individuals, as well as in preventing blindness in patients with glaucoma.

Laser Peripheral Iridotomy
Blue arrow points at Iridotomy

Laser Peripheral Iridotomy (LPI)

Laser Peripheral Iridotomy (LPI is beneficial in glaucoma therapy because the procedure is simple, safe, and relatively non-invasive. However, difficulties in determining indications, estimating prognosis, and progression with certainty in glaucoma, causing sharp clinical examination is needed as a guide in determining whether patients need to get an iridotomy laser or not.

The laser peripheral iridotomy procedure can be performed as a therapy and as a prophylaxis. LPI as therapy means that this procedure is beneficial in reducing intraocular pressure, while laser iridotomy as prophylaxis means that this procedure can prevent attacks and progression of glaucoma.

Laser Peripheral Iridotomy as Therapy

Laser peripheral iridotomy is performed for therapeutic purposes in two conditions, namely in acute attacks of closed-angle glaucoma and secondary glaucoma with iris bombe. Laser iridotomy shows a success rate of 65-76% in reducing intraocular pressure in acute attacks of closed-angle glaucoma.

The mechanism in closed-angle glaucoma is the mechanism of the pupillary block. LPI can effectively remove the blockade so that it can overcome the increased intraocular pressure that occurs. The formation of openings in the peripheral iris will eliminate the pressure difference between the anterior and posterior oculus cameras. The iris bombe and pupil blockade will be overcome through this laser procedure.

In acute attacks of closed-angle glaucoma may be accompanied by corneal edema conditions due to high intraocular pressure. Initial therapy in the form of both systemic and topical intraocular pressure-lowering drugs should be given first, and laser iridotomy is performed after the cornea is clear.

LPI contraindications

In addition to determining the exact case indicated for laser peripheral iridotomy, the clinician also needs to understand when this procedure should not be performed. Contraindications for laser peripheral iridotomy procedures are in the condition of neovascular glaucoma and closed-angle glaucoma without pupillary block mechanism.

Neovascular glaucoma is glaucoma caused by the formation of a fibrovascular membrane in the corner of the front eye chamber in response to ocular ischemic conditions such as in proliferative diabetic retinopathy or occlusion of the arteries or retinal veins. LPI tends not to benefit neovascular glaucoma because the pupillary blockade is not a mechanism involved in this case. Besides, if LPI is performed on neovascular glaucoma, there is a higher risk of iris bleeding.

Closed-angle glaucoma without pupillary block mechanisms includes phacomorphic glaucoma, iridocorneal-endothelial syndrome, secondary angle-closed glaucoma due to drugs (antipsychotics), or closed-angle glaucoma due to choroidal swelling.

Laser Peripheral Iridotomy as Prophylaxis

Laser peripheral iridotomy can be performed as a prophylactic measure in several conditions, such as in chronic primary angle-closure glaucoma (chronic PACG) and primary angle-closure suspect (PACS). However, not all PACS will develop into primary angle closure (PAC) or become PACG.

Based on the Asia Pacific Glaucoma Guidelines, PACS is defined as the contact between the peripheral iris and the posterior trabecular webbing at 180 ° of the angle of the front eye without accompanied by increased intraocular pressure or peripheral anterior synechiae. In contrast, PAC is defined as a PACS condition accompanied by increased intraocular pressure and peripheral anterior synechiae.

Several studies have been conducted to follow the progress of PACS after the LPI. He et al., In 2007, reported an average IOP decreased by 0.2 mmHg for every 10-degree wide-angle difference after laser iridotomy in PACS eyes. Whereas, Ramani et al. (2009) and Talajic et al. (2013) found no significant IOP changes in PACS eyes after laser iridotomy.

In a recent study in China in 2019, He et al. conducted a randomized controlled trial to determine LPI as PAC prophylaxis. In the study, 889 patients aged 50-70 years with a diagnosis of bilateral PACS, LPI were performed in one randomly selected eye, while the other eye was not treated. The observed outcome was the incidence of PAC after 72 months of follow-up, and the PAC incidence rate was 4.19 / 1000 eyes/year in the eye group receiving therapy while in the untreated group 7.97 / 1000 eyes/year.

The interpretation of the above study is that the incidence of PAC is very low among PACS patients, based on community-based screening. The prophylactic effect of LPI is not very significant. Therefore, the LPI procedure as prophylaxis is not widely recommended in PACS patients.

LPI Indications for Prophylaxis

Laser peripheral iridotomy as prophylaxis can be performed under the following conditions:

  • Chronic PACG to prevent acute and subacute glaucoma attacks
  • PAC to prevent the occurrence of PACG
  • PACS that are difficult to present for routine control or require recurrent pupillary dilatation such as patients with retinal disorders, diabetes mellitus or high myopia (require routine funduscopic examination with wide pupils)
  • PACS with positive provocative test results
  • Having a family history of PAC / PACG or previous one-eye history of PAC / PACG can be considered for prophylactic LPI, but many studies doubt this indication.