Re-establishment of the Physiological Pathway of Aqueous Humor Drainage in Primary Angle-Closure Glaucoma: Phacoemulsification, Goniosynechialysis, and Goniotomy

Abstract

P rimary angle-closure glaucoma (PACG) carries a 3-fold increased risk of severe bilateral visual impairment, and Asians account for > 70% of the PACG population worldwide. [1][2][3] The treatment principle aims to eliminate the angle-closure mechanisms to lower intraocular pressure (IOP). Phacoemulsification (PEI) can effectively resolve pupillary block (the most common angle-closure mechanism) and deepen the anterior chamber (AC). It is the logical choice to treat PACG eyes with coexisting cataracts as established by randomized controlled trials. [4][5][6][7] Even for patients with good central vision, the results of the EAGLE (effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma) study supported the approach of clear lens extraction as the initial treatment of choice for primary angle-closure with IOP ≥ 30 mm Hg and mild-to-moderate PACG. 8 Despite the level I evidence, only 60.6% of the patients who underwent initial clear lens extraction in the EAGLE study were medication-free at the end of the study period (36 mo). 8 For medically uncontrolled PACG or advanced glaucoma, combined phacotrabeculectomy is often required to control the IOP, 4 which could be technically demanding and result in more surgical complications than PEI alone, 9 not to mention the lifelong bleb-related and potentially blinding complications (eg, hypotony, bleb leakage, blebitis, and endophthalmitis). PEI alone may lower the IOP level comparable to that of phacotrabeculectomy but requires more long-term topical medical therapy. 4,5 The problem of medication side effects and the associated inconvenience of regular eye drops application could negatively impact patients' quality of life. 10 Cost of medication is also substantial and could be an opportunity cost to the health care system. 11,12 Prompt surgical intervention could reduce long-term medication use. 13 To improve quality of life and reduce the cost of treatment, additional IOP-lowering procedures should be considered. Ideally, the procedures should be safe, effective, and capable of limiting long-term complications and medication requirements.The variable degree of IOP reduction in PACG eyes that underwent PEI could be related to the amount of peripheral anterior synechiae (PAS). 14,15 Goniosynechialysis (GSL) re-exposes the trabecular meshwork (TM) for aqueous humor drainage. However, previous studies did not demonstrate additional IOP-lowering efficacy. 16,17 Irreversible damage to the TM may occur, especially after prolonged synechial closure. 18 Aggressive GSL for these eyes could lead to hyphema, inflammation flare-ups, and IOP spikes. This could lead to wipe-out syndrome, particularly for eyes with advanced visual field loss. 19 Complementary goniotomy (GT) may address the problem of dysfunctional TM-enhancement of aqueous humor outflow by removing the diseased TM and reducing the resistance of aqueous outflow to the Schlemm canal. It was reported to be effective and safe in PACG. [15][16][17][18][19]