Glaucoma

Glaucoma is a group of eye diseases causing optic nerve damage, potentially leading to vision loss. It is primarily associated with increased intraocular pressure (IOP) but can also occur with normal IOP. The condition progresses silently, often leading to irreversible vision loss if untreated.

Signs and Symptoms

Open-angle glaucoma typically presents without early symptoms, gradually causing peripheral vision loss, which can eventually affect central vision. Acute angle-closure glaucoma, a medical emergency, is characterised by sudden ocular pain, seeing halos around lights, red eye, very high IOP, nausea, and vomiting. Opaque specks in the lens, known as glaukomflecken, may also occur.

Risk Factors

Increased IOP is a significant risk factor, but other factors include age, family history, high blood pressure, and use of steroids. Genetic predispositions, ethnicity, particularly among African Americans, Latinos, and Asian-Americans, and specific medical conditions like diabetes and severe retinal vein occlusion can also increase risk.

Pathophysiology

Glaucoma primarily damages the optic nerve due to elevated IOP. In open-angle glaucoma, obstructed aqueous humour flow through the trabecular meshwork causes pressure build-up. In angle-closure glaucoma, the iris obstructs the drainage angle, leading to a rapid pressure increase. The exact mechanisms are not fully understood, but theories include mechanical damage from increased IOP and vascular issues reducing blood supply to the optic nerve.

Diagnosis

Glaucoma diagnosis involves comprehensive eye examinations, including IOP measurement, anterior chamber angle assessment, gonioscopy, retinal nerve fibre layer assessment via dilated fundus examination, corneal thickness measurement, and visual field testing.

Types

Glaucoma is broadly categorised into primary and secondary types. Primary includes open-angle and angle-closure glaucoma. Secondary glaucoma results from conditions like uveitis, trauma, or steroid use. Developmental glaucoma affects neonates or juveniles due to congenital abnormalities.

Visual Field Defects

Visual field defects in glaucoma are due to retinal nerve fibre layer damage, often manifesting in Bjerrum's area. Early defects include generalised depression and paracentral scotomas, progressing to arcuate scotomas and tubular vision in advanced stages.

Treatment

Medication

The primary goal is to lower IOP to slow disease progression. First-line treatments include prostaglandin analogues like latanoprost, which increase aqueous fluid outflow. Other medications include beta-blockers, alpha-adrenergic agonists, miotic agents, and carbonic anhydrase inhibitors.

Laser

Laser treatments like Argon Laser Trabeculoplasty (ALT) and Nd:YAG laser peripheral iridotomy (LPI) are used to enhance aqueous humour drainage or relieve angle closure.

Surgery

Surgical options include trabeculectomy, creating new drainage openings, and glaucoma drainage implants. Canaloplasty uses microcatheters to enhance drainage channels. Nonpenetrating deep sclerectomy (NPDS) and laser-assisted NPDS offer less invasive alternatives, reducing side effects.

Epidemiology

Globally, glaucoma affects over 44.7 million people and is the second leading cause of blindness. It is more prevalent in older adults and certain ethnic groups, notably African Americans and Asians.

History

Glaucoma's association with elevated IOP was first noted in 1622. Significant advancements include the invention of the ophthalmoscope in 1851, enabling optic nerve head examination, and the development of the first tonometer in 1905.

Research

Recent studies compare the effectiveness of eye drops versus surgical treatments like trabeculectomy for glaucoma. Neuroprotective agents and anti-VEGF treatments are also being looked at to improve outcomes.

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Self-assessment MCQs (single best answer)

Which of the following is a characteristic symptom of acute angle-closure glaucoma?

What is the primary goal of glaucoma treatment?

Which of the following treatments is NOT typically used for glaucoma?

What is a common visual field defect in early-stage glaucoma?

Which diagnostic tool is used to assess the optic nerve head in glaucoma patients?

Which ethnic group is at higher risk for developing glaucoma?

Which type of glaucoma is associated with a rapid increase in intraocular pressure due to iris obstruction?

What is the purpose of Argon Laser Trabeculoplasty (ALT) in glaucoma treatment?

Which medication class is considered first-line treatment for lowering IOP in glaucoma patients?

What is the term used to describe the opaque specks in the lens associated with acute angle-closure glaucoma?