• Clinical science

Glaucoma

Abstract

Glaucoma is a group of eye diseases associated with acute or chronic destruction of the optic nerve with or without concomitant increased intraocular pressure (IOP). In the US, glaucoma is the second leading cause of blindness in adults following age-related macular degeneration (AMD). The two main types are open-angle glaucoma and angle-closure glaucoma. Open-angle glaucoma accounts for 90% of all cases of glaucoma, is slowly progressive, and is initially often asymptomatic, but leads to bilateral peripheral vision loss over time. With appropriate screening (e.g., fundoscopy, gonioscopy, and tonometry) and treatment that lowers IOP (e.g. topical prostaglandins), progression can be stopped before severe damage occurs. Angle-closure glaucoma, on the other hand, is sudden onset and characterized by a painful, red, and hard eye in combination with frontal headache, blurry vision, and halos appearing around lights. Immediate initiation of medical therapy (e.g. timolol eye drops and IV acetazolamide) is crucial to rapidly decrease IOP and prevent vision loss.

Definition

  • Open-angle glaucoma: (also primary or chronic glaucoma): generally bilateral, progressive loss of optic nerve fibers with open chamber angles (often with increased IOP), not caused by another systemic or local condition
  • Angle-closure glaucoma: (also narrow-angle or acute glaucoma): sudden and sharp increase in intraocular pressure caused by an obstruction of aqueous outflow (most commonly as a result of an occlusion of the chamber angle)
  • Congenital glaucoma: glaucoma that is present at birth and is due to improper development of the eye's drainage system, causing increased IOP and consequent damage of the optic nerve

References:[1]

Epidemiology

  • Second leading cause of blindness in adults in the US following age-related macular degeneration (AMD)
  • ∼ 2.3 million cases of glaucoma in the US
    • Vision impairment in ∼ 10% of patients
    • Blindness in ∼ 5% of patients

References:[2][3]

Epidemiological data refers to the US, unless otherwise specified.

Overview

Important types of glaucoma
Open-angle glaucoma Angle-closure glaucoma
Risk factors
Clinical features
  • Initially often asymptomatic
  • Bilateral, progressive visual field loss
  • Sudden onset
    • Unilateral red, hard, and severely painful eye
    • Frontal headaches
    • Vomiting, nausea
    • Steamy cornea and blurred vision
    • Dilated, nonreactive pupil
Treatment
  • Prostaglandin eye drops or laser trabeculoplasty
  • In refractory cases: surgical trabeculectomy
  • Topical timolol, apraclonidine, and IV acetazolamide
  • Curative treatment: laser peripheral iridotomy
  • No mydriatic drugs!

References:[3]

Pathophysiology

Basic physiological principles

References:[4][5]

Open-angle glaucoma

Etiology

  • Primary cause unclear
  • Risk factors

Pathophysiology

Clinical features

  • Initially often asymptomatic
  • Over time, nonspecific symptoms such as mild headaches, impaired adaptation to darkness
  • Generally bilateral, progressive visual field loss (from peripheral to central)
  • Halos around lights may occur.

Diagnostics

  • Slit lamp examination of the anterior segment: normal appearing anterior chamber angle
  • Tonometry: measure IOP (standard values range between 10–21 mm Hg)
  • Gonioscopy : to rule out angle-closure glaucoma
  • Fundoscopy: cupping and pallor of optic disc
  • Perimetry: visual field testing to detect blind spots in the visual field

Therapy

  • Indication: IOP > 25 mm Hg
  • Conservative (first-line): topical prostaglandins are most effective and usually used initially; other drugs (with a different mechanism) may be added if unsuccessful
  • Alternative first-line treatment: laser trabeculoplasty
  • Refractory cases: surgical trabeculectomy

Prevention

  • For all individuals > 40 years, a regular eye examination by an ophthalmologist or optometrist is recommended. This should include:

References:[6][7][8][9][10][11][12]

Acute angle-closure glaucoma

Etiology/Risk factors

Pathophysiology

Clinical features

  • Sudden onset of symptoms
  • Unilaterally inflamed, reddened, and severely painful eye (hard on palpation)
  • Frontal headaches, vomiting, nausea
  • Blurred vision and halos seen around light
  • Cloudy cornea (opacification)
  • Mid-dilated, irregular, unresponsive pupil
  • Complications: rapid permanent vision loss due to ischemia and atrophy of the optic nerve

Diagnostics

  • Rock-hard globe on palpation
  • Slit lamp examination of the anterior segment: narrow anterior chamber angle, shallow anterior chamber
  • Gonioscopy (gold-standard)
  • Tonometry (if gonioscopy is unavailable): IOP

Do not use mydriatic drugs (e.g., atropine and epinephrine) during ophthalmologic examination in patients with suspected angle-closure glaucoma! Also don't cover the eye, since darkness induces mydriasis and worsens the condition!

Treatment

  • First-line: drugs can be used alone but are usually given in combination
  • Topical cholinergics (e.g., pilocarpine) can be added once IOP is < 40 mm Hg (contraindicated in cases of lens-induced glaucoma, e.g., in lens luxation)
  • Analgesics and antiemetics
  • Definitive surgical treatment
    • Perform once the acute attack is controlled.
    • Shunt from posterior to anterior chamber through the peripheral iris
      • Neodymium-YAG laser iridotomy
      • Open surgery (peripheral iridectomy)

Blood supply to the optic nerve may be impaired by lowering blood pressure. → No systemic blood pressure reduction in acute glaucoma patients.
Immediate ophthalmic treatment is necessary, as the eye is at risk of being irreversibly damaged!

References:[13][14][1][15][16][17]

Congenital glaucoma

Epidemiology

  • < 1% of children are born with the condition in the US.
  • Bilateral in ∼ 75% of cases
  • Most cases are diagnosed within the first year of life.

Etiology

Pathophysiology

Clinical features

  • Buphthalmos
  • Enlarged corneal diameter
  • Corneal clouding
  • Photophobia
  • Excessive tearing (epiphora)
  • In secondary congenital glaucoma, symptoms of the underlying disease

Diagnostics

  • ↑ Corneal diameter and ↑ diameter are diagnostic.
  • Genetic testing: CYP1B1 gene
  • In secondary congenital glaucoma, further diagnostics depending on the underlying disease

Therapy

  • Absolute indication for surgery!