Who needs an iridotomy?

Angle closure glaucoma (ACG) is one of the leading causes of global blindness. Recent population based research on Chinese subjects in Singapore and a southern Indian population found high rates of ACG among those populations.12 Close to 2% of individuals over the age of 40 were found to have ACG in these studies. Given that almost half of the world's population lives in China and India, millions of individuals are at risk of ACG and may benefit from better screening strategies to identify them before glaucoma develops.13

However, the decision to perform a laser peripheral iridotomy (LPI) on a patient with a narrow angle is often highly subjective. What is an “occludable” angle? If one can see trabecular meshwork is the patient “safe.” If one cannot, is the patient at significant risk? What proportion of the angle needs to be visible? What should be done in the developing world setting where an ACG suspect is unlikely to receive a second eye examination in the near future?

A recent World Health Organization (WHO) sponsored meeting on glaucoma blindness worldwide proposed that a new nomenclature be employed for describing individuals with ACG. Those with 90 degrees of angle in which the trabecular meshwork is visible who have glaucomatous optic nerve damage have “primary ACG,” while those with similarly closed angles and elevated eye pressure or peripheral anterior synechiae (PAS) have “primary angle closure.” The termglaucoma is only used for those with glaucomatous optic neuropathy and visual field loss. A third, important category of patients is those with narrow angles as described above with no evidence of glaucoma or damage to the angle (that is, no elevated IOP or peripheral anterior synechiae). These individuals are simply described as having “narrow angles,” not having angle closure glaucoma. How to …