This lecture is on primary and secondary angle closure glaucoma. The contents of the lecture will include epidemiology, classification, risk factors, clinical features, and management principles. Primary angle closure glaucoma, or PACG, is a leading cause of blindness in Singapore. 6% of the population over 40 years old has primary angle closure suspect, or PACS. And 2% has primary angle closure, or PAC. The age-standardized prevalence of PACG among the Singapore Chinese population is 1.2%, with a higher proportion of blindness compared with primary open angle glaucoma. The incidence of acute primary angle closure or APAC in the population 40 years and older is 12.2 per 100,000 people per year. The epidemiology of secondary glaucoma is less well characterized than primary glaucoma. It accounts for 16% of the glaucoma in the Singapore Chinese population aged 40 years and older. Ritch described the mechanisms of angle closure based on the anatomical level at which the forces act to change the angle configuration, and can be classified as follows. Level I– Pupillary block. This is the most common form of angle closure. There’s resistance to aqueous flow through the pupil in the area of iridolenticular contact. This creates an increased pressure gradient between the anterior and posterior chambers, causing anterior bowing of the iris, narrowing of the angle and iridotrabecular contact. Relative pupillary block accounts for more than 90% of angle closure. Other classes of pupillary block include posterior synechiae. Level II– Angle closure originating at the level of the ciliary body. Plateau iris configuration refers to an angle appearance in which the iris root angulates forward and centrally, due to an anteriorally positioned pars plicata which mechanically holds the ciliary body against the trabecular meshwork. Plateau iris syndrome occurs when the configuration is present along with angle closure. Other causes of angle closure at this level include iris and ciliary body cysts, or tumors. Level III– Lens-induced angle closure. Abnormalities in size or position of the lens, including lens intumescence, anterior lens subluxation and dislocation may lead to angle closure. Level IV– Retrolental factors. Forces posterior to the lens which push the lens-iris diaphragm forward can result in angle closure. Causes include aqueous misdirection, choroidal effusion, and ciliary body rotation, angle closure of the scleral buckle, panretinal photocoagulation, retinal vein occlusion, and posterior segment tumors. PAS is another cause of angle closure. Primary angle closure can be classified into the following stages. PACS is when there’s at least 180 degrees of irido-trabecular contact, without PAS or elevated IOP or glaucomatous optic neuropathy. PAC is when there is at least 180 degrees of irido-trabecular contact with PAS and elevated IOP, without glaucomatous optic neuropathy. PACG is PAC with glaucomatous optic neuropathy. Risk factors for angle closure include older age, female gender, East Asian or Inuit ethnicity, shallow anterior chamber, shorter axial length, thicker lens, more anterior lens position, and family history of angle closure. Clinical features of primary angle closure. Most patients are asymptomatic in early stages, until extensive visual field loss. They may have episodes of intermittent angle closure or a family history of glaucoma. The patient should be asked about the use of topical or systemic medications that may induce angle narrowing, such as sulfonamides, topiramate, phenothiazines, and anticholinergics. Visual acuity is normal unless there’s advanced glaucoma. Hyperopic eyes, especially in older patients, have narrower angles. However, this is not an infavorable association. We can perform the Van Herick’s technique of assessing peripheral anterior chamber depth by directing a narrow beam of light perpendicular to the temporal limbus. If the peripheral anterior chamber depth is less than or equal to one quarter of the corneal thickness, there’s a risk of angle closure. The gold standard diagnostic procedure for angle closure is gonioscopy to identify irido-trabecular contact. Indentation should be done to look for PAS, the IOP could be raised, and there may be signs of previous APAC, such as spiral iris atrophy, glaukomflecken, and there may be glaucomatous optic neuropathy. Clinical features of acute angle closure include ocular or periocular pain with headache, nausea, vomiting; history of intermittent blurring of vision with halos; IOP more than 21; conjunctival injection; corneal epithelial oedema; mid-dilated unreactive pupil; shallow anterior chamber with narrow angles. Clinical features of secondary angle closure. In plateau iris, the double hump sign is set on indentation gonioscopy. As the iris follows the convexity of the anterior lens capsule, [INAUDIBLE] posteriorally and rises over the anteriorally-placed ciliary body. In lens-induced angle closure, there’s lens intumescence, dislocation, or phacodonesis. In aqueous misdirection, there’s axial anterior chamber shallowing, patent peripheral iridotomy, history of intraocular surgery, with UBM showing anterior rotation of the ciliary body. In neovascular glaucoma, there’s iris or angle neovascularization with underlying condition of retinal ischaemia. In uveitic glaucoma, there’s intraocular inflammation with PS or PAS. In choroidal effusion and ciliary body swelling, UBM will show choroidal detachment and uveal effusion. Anterior segment imaging can be considered. There’s good evidence demonstrating general agreement between findings on gonioscopy and ASOCT and UBM. These technologies are useful in evaluating secondary causes of angle closure. The five year risk of progression of untreated PACs to PAC is 22% and that of untreated PAC to PACG is 28%. If the patient has a clear lens or mild cataract, laser peripheral iridotomy should be performed to relieve pupil block and widen the angle. If the patient has a visually significant cataract, this should be removed. Cataract extraction removes pupil block with greater opening of the angles, reduction of PAS, and is also effective in managing APAC. Cataract surgery can be combined with goniosynechiolysis to remove PAS. Once a close angle has been opened, any residue or pressure elevation can be treated with antiglaucoma medications, and even filtration surgery. A significant proportion of patients with PACG with or without previous APAC require further treatment to control the IOP. Management of APAC is aimed at lowering the IOP quickly and relieving the pupil block. Medical therapy includes systemic carbonic anhydrase inhibitors and topical antiglaucoma medications. Topical steroids are also given to control the intraocular inflammation. Once the IOP’s lower, [INAUDIBLE] can be used to constrict the pupil. Corneal indentation can also be performed to mechanically open the angle. Laser iridotomy should then be performed as soon as possible. If the APAC cannot be medically broken, alternative strategies to lower the IOP, such as laser iridoplasty, AC paracentesis, and pupilloplasty can be done. Alternative strategies to release the pupil block include lens extraction with or without goniosynechiolysis, and trabeculectomy or phacotrabeculectomy refractory cases. The fellow eye should also be evaluated, and should receive a prophylactic laser iridotomy promptly, if the angle is narrow, since half of them can develop APAC within five years. Management of secondary angle closure. Argon laser peripheral iridoplasty is effective in eliminating residual appositional closure after laser iridotomy in plateau iris syndrome. Lens extraction should be performed in lens-induced glaucoma. Medical therapy for malignant glaucoma include the concurrent use of antiglaucoma medications, topical steroids, and cycloplegic eye drops. 50% success has been noted with medical therapy within four to five days. YAG hyaloidotomy can be done to disrupt the anterior [INAUDIBLE] phase, [INAUDIBLE] and cyclodiode laser photocoagulation can be done to break the cycle of aqueous misdirection. In cases of laser and medical therapy failure, vitrectomy can be done. In neovascular glaucoma, antiglaucoma medications, topical steroids, and atropine should be started. Pan retinal photocoagulation should be done for retinal ischaemia. The angles are initially open and PAS formation can eventually close the angle. Glaucoma drainage implants is widely accepted as a primary surgical procedure in patients with uncontrolled IOP with reasonable visual potential. As the tube bypasses the hypovascular membrane in the angles. Filtration surgery has a higher risk of failure, because of the risk of bleeding and post-op progression of type of hypovascular membrane. Trabeculectomy can be augmented with mitomycin C and preoperative intravitreal bevacizumab. In eyes with poor visual potential, ciliary body ablation can be done to relieve the pain from the uncontrolled higher IOP. In uveitic glaucoma, inflammation can produce secondary angle closure with pupillary block due to PAS, or without pupillary block from PAS. Control of the inflammation is important, together with the use of antiglaucoma medications. PI should be done for pupil block. Trabeculectomy augmented with mitomycin C for glaucoma drainage implant can be used if the IOP remains uncontrolled. Cilary body swelling secondary to vortex vein obstruction for extensive PRP or CRVO producing angle closure is usually self limiting. Ciliary body swelling can also occur secondary to drug use. This is an idiosyncratic reaction causing relaxation of [INAUDIBLE] with anterior rotation of the ciliary body, leading to anterior displacement of the iris lens diaphragm. It presents as bilateral angle closure. The management requires stopping of the drug, aqueous suppressants, and cycloplegics. In summary, angle closure glaucoma is an aggressive, visually destructive disease. Primary and secondary angle closure glaucoma are distinct clinical entities. The mechanism of angle closure needs to be identified so that treatment can be directed at the underlying pathophysiology. Thank you.