Walid Raslan MBBS, MSc1
1Western Eye Hospital, London, United Kingdom
Introduction
Angle-closure glaucoma (ACG) is a condition that leads to optic nerve neurodegeneration caused by increased intraocular pressure (IOP). It’s an ophthalmic emergency that may cause irreversible visual impairment if left untreated. ACG causes can be classified into Primary and Secondary causes. This article will focus on Primary Angle Closure Glaucoma (PACG).
In this article, we will briefly outline the pathophysiology, diagnosis, and management of acute PACG.
Pathophysiology
In PACG, IOP increase is mainly due to physical obstruction of the anterior chamber (AC) angle leading to an impaired outflow of aqueous humour (1). This obstruction is mainly caused by pupillary block, in which there is resistance to the aqueous passage from the posterior chamber (where it’s produced) to the AC due to the apposition of the iris to the lens (2).
The main risk factors for developing ACG are (3):
- Age>60y
- Female gender
- Family history of angle closure glaucoma
- Asian and Inuit ethnicities
- Hypermetropia (shorter axial length)
- Certain medications such as antidepressants, B2 agonists, and anticholinergics
Diagnosis
Patients usually present with sudden onset severe ocular pain, eye redness, blurry vision, nausea, and vomiting.
PACG is diagnosed clinically. On examination, there are common signs that could be recognised (3):
- Injected conjunctiva
- Cloudy cornea
- Fixed mid-dilated pupil
- High IOP
- Shallow AC
Gonioscopy is the golden standard for assessing ACG, it allows physicians to assess the width of the angle. Various systems of angle grading are used by ophthalmologists nowadays. Three systems are widely used for grading: Scheie, Shaffer, and Spaeth.
Management
The main goals when treating Acute ACG are:
- Lowering IOP via keeping the anterior chamber angle open and maintaining the process of aqueous outflow
- Relieving the symptoms
- Preventing the progression of the disease and subsequent optic nerve damage
This can be achieved with a combination of topical and systemic medicines as well as laser procedures (4).
Topical:
- Beta-blockers
- Selective alpha agonists
- Carbonic anhydrase inhibitors
- Miotics (pilocarpine 2%)
Systemic:
- Carbonic anhydrase inhibitors (acetazolamide); 500mg orally is given.
Laser Procedure:
- Laser Peripheral Iridotomy (LPI) is the most preferred treatment of patients with acute ACG and should be performed as soon as possible on both the affected eye and the fellow eye as a prophylactic measure.
Conclusion
Acute PACG is an ocular emergency that can have a profound impact on vision. It may lead to irreversible visual impairment if not treated as soon as possible. Thus, identifying this condition and immense management is important to prevent optic neuropathy. This is because studies have shown that the longer the acute attack lasts, the worse the visual outcome is, despite the initial IOP measurement (5). Therefore, although the management of acute PACG can be challenging, early management is key in preventing visual loss.
References
- Leung CK, Cheung CY, Li H, et al. Dyanamic analysis of light-dark changes of the anterior chamber angle with anterior segment OCT. IOVS. 2007;48:4116-22.
- EUROPEAN GLAUCOMA SOCIETY 2017. European Glaucoma Society Terminology and Guidelines for Glaucoma, 4th Edition – Chapter 2: Classification and terminology<br/>Supported by the EGS Foundation. Part 1: Foreword; Introduction; Glossary; Chapter 2 Classification and Terminology, 101, 73-127.
- AMERASINGHE, N. & AUNG, T. 2008. Angle-closure: risk factors, diagnosis, and treatment. Progress in Brain Research, 173, 31-45.
- DENNISTON, A. K. O. & MURRAY, P. I. 2014. OXFORD HANDBOOK OF OPHTHALMOLOGY.
- David R, Tessler Z, Yassur Y. Long-term outcome of primary acute angle-closure glaucoma. Br J Ophthalmol. 1985;69:261–262