Primary Angle Closure

Primary angle closure (PAC) disease is apposition of the peripheral iris to the trabecular meshwork impeding aqueous outflow, without an identifiable secondary cause. It is classified into stages:

• Primary angle closure suspect (PACS): 180 degrees or more of iridotrabecular contact on gonioscopy, normal pressure, no damage.
• Primary angle closure (PAC): iridotrabecular contact with raised pressure or peripheral anterior synechiae, but no optic neuropathy.
• Primary angle closure glaucoma (PACG): angle closure with glaucomatous optic neuropathy.
• Mechanisms (often combined): pupillary block (commonest), plateau iris configuration, thick or anteriorly positioned lens, and anterior rotation of the ciliary body.
• Risk factors: hypermetropia and short axial length (under 22 mm), shallow anterior chamber, age over 50, female sex (3 to 4 times), East Asian and Inuit ancestry, family history, and pseudoexfoliation.
• PACG accounts for about half of glaucoma blindness worldwide despite lower prevalence than POAG.

• Often asymptomatic (chronic form), or intermittent subacute attacks of blurred vision with haloes, mild eye ache and headache, particularly in dim light or when reading.
• Shallow anterior chamber (van Herick grade 1 or 2), narrow limbal chamber depth.
• Pressure may be normal or raised; optic disc may be normal or cupped according to stage.
• Peripheral anterior synechiae and iris atrophy in advanced disease.

• Gonioscopy (dynamic, with indentation) to identify closure (inability to see the posterior trabecular meshwork in 180 degrees or more) and peripheral anterior synechiae.
• Anterior segment optical coherence tomography and ultrasound biomicroscopy (iris configuration, plateau iris, ciliary body, lens vault, angle opening distance).
• Axial length and anterior chamber depth biometry.
• Tonometry, optic disc assessment, OCT and visual fields.
• Dark room provocative tests are no longer favoured.

• Laser peripheral iridotomy (neodymium doped yttrium aluminium garnet, Nd:YAG, 3 to 8 mJ, or argon) is the first line treatment to relieve pupil block, for PACS with risk features (narrow angle, family history, need for dilation, symptoms) and for PAC and PACG. Pretreat with pilocarpine 1 to 2 percent and apraclonidine 1 percent, post laser prednisolone acetate 1 percent four times daily for 5 to 7 days.
• Lens extraction (phacoemulsification with intraocular lens) for PAC and PACG with cataract or with persistent elevated pressure after iridotomy; clear lens extraction is an effective first line therapy in older patients, reducing pressure by about 4 to 6 mmHg.
• Laser peripheral iridoplasty for plateau iris, and goniosynechialysis during cataract surgery to open synechially closed angles.
• Medical therapy for raised pressure: aqueous suppressants (timolol 0.5 percent, dorzolamide 2 percent, brimonidine 0.2 percent); prostaglandin analogues for open portion of the angle; pilocarpine 1 to 2 percent three or four times daily can be used before iridotomy but may worsen block in plateau iris or in thick lens.
• Glaucoma surgery (trabeculectomy with mitomycin C or combined phacotrabeculectomy, drainage devices) when pressure remains uncontrolled despite iridotomy and lens extraction, or with advanced damage.
• Drugs to avoid in suspect eyes before treatment: dilating drops, topiramate, anticholinergics, sympathomimetics, tricyclics, and oral decongestants.
• Review every 3 to 6 months initially, with repeat gonioscopy annually, and examination of first degree relatives.