Question 9: What is the role of laser peripheral iridotomy in the treatment of patients with pigment dispersion syndrome or pigmentary glaucoma?

Question 9: What is the role of laser peripheral iridotomy in the treatment of patients with pigment dispersion syndrome or pigmentary glaucoma?

Answer:

In pigment dispersion syndrome and pigmentary glaucoma, reverse pupillary block results from posterior bowing of the iris, causing irido-zonular contact and subsequent pigment release. This also restricts the flow of aqueous humour and disrupts aqueous fluid dynamics.

A peripheral iridotomy involves the use of a laser to create an opening in the iris to serve as an alternative channel for aqueous flow. The rationale for performing a YAG laser peripheral iridotomy is to reduce the reverse pupillary block by flattening the iris, reducing irido-zonular contact and decreasing active pigment dispersion.

There has, however, been some debate about the efficacy of peripheral iridotomies in pigment dispersion syndrome, particularly when the patient has manifest glaucoma.

A Cochrane review article analysed the results of five randomised controlled trials of YAG laser iridotomy vs no laser iridotomy in 260 eyes of 195 participants with pigment dispersion syndrome or pigmentary glaucoma. The primary outcomes were visual field progression, onset of visual field changes in patients with pigment dispersion syndrome and ocular hypertension, and mean reduction in IOP at one year. Secondary outcomes included logMAR VA at six and twelve months, change in anterior chamber depth, change in iris configuration and pigment accumulation in the anterior chamber.

The authors noted that along the continuum of pigment dispersion to pigmentary glaucoma, different pathogenic stages can be identified. In the early stages, pigment that has been dispersed obstructs the trabecular meshwork, and granules of pigment are phagocytosed by the endothelial cells of the trabecular meshwork. In the later stages of the disease the trabecular endothelial cells become overloaded with pigment and eventually die, which can result in an increase in IOP. At this point, damage is probably irreversible. The authors hypothesised that treatment with laser peripheral iridotomy may have different success rates at various stages of the disease, with the treatment likely to be more effective earlier in the disease process.

The authors found that there was a lack of high-quality evidence on the effectiveness of peripheral iridotomy in the treatment of pigment dispersion syndrome or pigmentary glaucoma.

End of answer