Glaucoma is the number one cause of blindness in Hong Kong. This is a condition in which there is irreversible damage and loss of optic nerve tissues, often as a result of increased pressure within the eyeball (intraocular pressure "IOP"). It is classified into angle-closure and open-angle types. While the angle-closure form contributes only a small proportion in Western countries, this is a common type in the Far East including Hong Kong.

　　The angle-closure form is usually presented with an acute attack in which there is a sudden rise of IOP of up to two to four times that of upper limit of normal IOP (normal range is ~6-21 mmHg). Patients usually experience sudden blurring of vision, seeing halo around lights, severe eye pain or even headache, nausea and vomiting. Besides the optic nerve, the cornea, the lens and the drainage angle may all be damaged by high IOP. Acute angle-closure glaucoma can lead to permanent blindness, if not promptly treated.

　　Conventional treatment for acute angle-closure glaucoma involves two stages. The immediate first-line treatment is to reduce and normalize the IOP by the use of both systemic (oral and intravenous) and topical (eye drops) anti-glaucoma medications. Long duration of sustained high IOP will damage the nerve tissue. When the IOP is adequately reduced and the cornea is clear enough, laser peripheral iridotomy to make a hole in the iris tissue can be performed to prevent recurrence of the disease.

　　However, this conventional first stage treatment may not be optimal, as anti-glaucoma medications take time to work, and sometimes, may fail to control the IOP altogether. More, systemic medications often cause annoying side effects, such as drowsiness, loss of appetite, skin numbness, polyuria and polydipsia. Some may even cause rare but potentially life-threatening complications, such as congestive heart failure, pulmonary edema and electrolyte imbalance.

Argon Laser Peripheral Iridoplasty (ALPI)

　　In 1997, The Chinese University of Hong Kong pioneered the use of "immediate" argon laser peripheral iridoplasty (ALPI) as a first-line treatment for acute primary angle-closure glaucoma, replacing conventional systemic medications altogether. ALPI involves the placement of a ring of contraction burns on the peripheral iris to contract the iris tissue near the drainage angle. This mechanically pulls open the angle, thus lowering the IOP and thereby clearing up the cornea and allowing the subsequent laser iridotomy to be performed. It is considered a more effective and optimal alternative to the traditional therapy as it relieves the very unpleasant symptoms of acute primary angle-closure glaucoma more promptly without the use of any systemic anti-glaucoma medications. Since then, CUHK has been engaged in the study of the efficacy and safety of ALPI as an alternative treatment for acute primary angle-closure glaucoma. Up to now, more than 200 cases of acute primary angle-closure glaucoma have been treated with immediate ALPI and over 95% have had their eye pressure effectively reduced by ALPI alone. None of the patients in the studies suffered any complications arising from ALPI.

　　"Immediate ALPI has many advantages over conventional systemic eye pressure-lowering medications in the management of acute primary angle-closure glaucoma as it reduces IOP significantly more rapidly than systemic medications in the first 2 hours after the initiation of treatment, which means less permanent damage to the optic nerve and other ocular tissues. Besides, being free from the potential systemic side effects of the conventional systemic medications, it is of particular value in those patients who are at risk from systemic complications," said Professor Dennis Shun-chiu Lam, Chairman of the Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong.

Paracentesis: Another Alternative Immediate Treatment for Managing Acute Angle-closure Glaucoma

　　Despite the impressive efficacy and reassuring safety profile of ALPI in the immediate treatment of acute primary angle-closure glaucoma, there are always situations when ALPI is not logistically possible. First of all, a round-the-clock emergency ALPI service would require the availability of trained laser experts 24 hours a day. Secondly, an expensive argon laser machine also needs to be accessible and operative round-the-clock. The provision of both is difficult even in Hong Kong, due to increasingly limited resources. It would be impossible in the vast rural expanses of countries like China.

　　Acute rise in IOP sometimes occurs after cataract surgery. It is common practice amongst cataract surgeons to perform anterior chamber paracentesis for patients with IOP spike for rapid control of IOP and relief of symptoms. In 2000, we started to treat acute primary angle-closure glaucoma with immediate anterior chamber paracentesis, which rapidly reduces the IOP, and relieves symptoms. The effect is instantaneous, and unlike ALPI, no special equipment or laser expertise is needed in the emergency setting. It is suggested that paracentesis may be an effective and safe procedure in acute primary angle-closure glaucoma and is certainly worth a consideration in those situations when immediate ALPI is not possible.

Conclusions

　　Acute primary angle-closure glaucoma is a potentially blinding disease if not promptly treated. Nowadays, safe and effective therapies are widely available. We would strongly recommend members of the public with symptoms suggestive of acute primary angle-closure glaucoma (sudden blurring of vision, seeing halo around lights, severe eye pain or even headache, nausea and vomiting) to seek medical attention immediately. Early treatment can save vision.

　　In addition to the conventional systemic glaucoma medications, ALPI and paracentesis are new alternative immediate treatments that are available in modern eye care. Eye doctors will judge which treatment modality is best suited for a particular patient, based on clinical circumstances.