lower initial IOP, and delayed presentation (Nolan et al., 2000).

Fellow eye of APAC

The fellow eye will have the same dimensions as the attack eye and therefore is at high risk of APAC as well. Therefore a prophylactic PI should be carried out for the fellow eye. This will prevent APAC, however 10% may still have a rise in IOP over time and therefore require close monitoring including regular gonioscopy. Figure 5 is a flow diagram for the management of APAC.

Chronic primary angle-closure glaucoma (CACG)

The aim of treatment is to eliminate the underlying pathophysioloical mechanism causing the angle closure (mainly pupil block and peripheral angle crowding/plateau iris).

Laser peripheral iridotomy

All CACG patients should undergo PIs. However, this is an unsatisfactory long-term therapy in the sense that additional treatment is often required, particularly for eyes with GON. The majority of patients require further medication or surgery to control IOP (Alsagoff et al., 2000).

Laser iridoplasty

If the patient has plateau iris or peripheral crowding of the angle, i.e. the angle remains occludable after PI, then peripheral iridoplasty can be considered. It should be carried out early in the disease course as laser iridoplasty might not be effective when PACG is well established or when medical therapy has already failed, or in the presence of extensive PAS.

Medical therapy

The need for further medical therapy after iridotomy is determined by IOP and the extent of glaucomatous damage. This is common in Asian

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patients and can be difficult to manage (Ritch and Lowe, 1996b). It is known as ‘‘residual CACG after iridectomy or iridotomy.’’ Usually, nonpupil block mechanisms including lens factors, plateau iris, and damage to the trabecular meshwork, are the cause (Ritch and Lowe, 1996b).

Medical therapy entails the use beta-adrenergic agonists, alpha2 adrenergic agonists, mitotics, topical carbonic anhydrase inhibitors, and prostaglandins. Of note long-term miotic treatment in the absence of an iridotomy may expedite the development of acute angle closure. Low dose pilocarpine can be used as an alternative to iridoplasty in plateau iris syndrome. Studies have shown that the prostaglandin, latanoprost, is more effective than the beta-blocker, timolol, in lowering IOP in PACG patients. It is thought that latanoprost enhances aqueous humor access to the ciliary body via the still open part of the drainage angle (Aung et al., 2000; Chew et al., 2004).

Trabeculectomy

This is indicated when the IOP cannot be controlled by laser iridotomy or medication, if there is evidence of continuing glaucomatous damage, poor compliance or intolerance to medical treatment, or poorly controlled glaucoma at the time of planned cataract surgery. The use of antiscarring agents is also similar to that of POAG, i.e. eyes at high risk of failure of surgery (e.g. those with previous failed trabeculectomy), eyes with advanced disease (extensive PAS, opticnerve damage, and visual-field loss), and eyes on multiple medications (Aung, 2006).

Lens extraction

It is postulated that removal of the lens leads to deepening of the anterior chamber, resulting in reduction of angle crowding and the relief of pupil block. A prospective case series carried out in Hong Kong found both the IOP and requirement for glaucoma drugs reduced significantly after cataract extraction (Lai et al., 2006).