ANGLE CLOSURE: A TO Z

A population-based study from South India reported 22% of PACS patients progressed to PAC and 29% of PAC patients progressed to PACG over 5 years.

Mechanisms of angle closure

Mechanisms responsible for angle-closure are described in terms of anatomical location of obstruction to aqueous flow.

•       Pupillary block mechanism

•       Anomalies at the level of the iris and/or ciliary body (“Plateau iris configuration”)

•       Anomalies at the level of the lens

•       Anomalies posterior to the lens (e.g. aqueous misdirection syndrome)

New anatomical risk factors for PAC

•       Anterior chamber: width, area and volume

•       Iris: thickness, area, and curvature

•       Lens: lens vault

New altered physiology/dynamic factors

•       Iris: change in volume with dilatation

•       Choroid: choroidal expansion/effusion

•       Ciliary body: anterior rotation

Management of PAC:

1.      Laser peripheral iridotomy (LPI)

            LPI only treats one of the angle-closure mechanisms (pupillary block); non-pupillary blockage PAC may remain.

The Zhongshan Angle-Closure Prevention Trial

Objective: to determine longitudinal changes in angle configuration in eye with PACS treated by LPI.

Conclusions: angle width increased markedly after LPI, remained stable for 6 months, and then decreased significantly by 18 months after LPI.

2.        Clear lens extraction for PACG

            Clear lens extraction (CLE) should be considered in patients with PACG especially with hyperopia, and/or a thick and anteriorly vaulted lens. However, CLE is not an established conventional treatment and may even be controversial.

Challenges for CLE:

•       Shallow anterior chamber

•       Large bulky lens

•       Iris atrophy secondary to ischemia

•       Associated zonular weakness

Benefits

•       Reverse anatomical predisposition and defect

•       Reduce IOP and IOP-lowering drugs

•       Prevent pupillary block and acute angle closure

•       Prevent progression of disease (based on IOP reduction)

 

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