Glaucoma

Overview

Eye Cells

Video 4.1: Intraocular pressure​

Physiology of Intraocular Pressure (IOP)

  • Circulation of the aqueous humour, the physiological fluid of the eye:
    • Secreted by the ciliary body in the posterior chamber,
    • Passes through the pupil (between the iris and the lens),
    • Then fills the anterior chamber,
    • Is reabsorbed by the irido-corneal angle,
    • Is filtered by the trabeculum and joins Schlemm’s canal.
  • Mechanism that is at the origin of regulation of intraocular pressure (IOP).
  • The optic nerve:  
    • Connects the retina to the brain and ensures transmission of images as nerve impulses.
    • The value of the IOP determines the proper perfusion of the optic nerve. 

Definition

A disease characterised by a progressive lesion of the optic nerve caused in large part by increased Intraocular Pressure. The excess pressure inside the eye compresses the nerve fibres of the retina and of the optic nerve, resulting in slow deterioration of the visual field which can progress to loss of vision.

The following are differentiated:

  • Primary types of glaucoma:
    • open angle
    • closed angle
  • Glaucoma secondary to another disease (1).

Epidemiology

  • On a world-wide scale:
    • One of the primary causes of decreased visual acuity: 2%. (2).
    • Accounts for 12.3% of cases of blindness world-wide, i.e. about 4.5 million blind persons because of primary glaucoma (3).
    • The leading cause of blindness in the industrialised countries.
  • In France, glaucoma may be responsible for 10 to 15% of cases of blindness and/or decreased vision, i.e. about 15,000 cases. (4)

Risk factors

Elevated IOP increases the risk of glaucoma, but does not always result in a lesion to the optic nerve.

  • Age
    • A very low risk before 45 years of age (age of presbyopia).
    • Average risk between 55 and 75 years of age.
    • High risk after 80 years of age.
    • Existence of congenital types of glaucoma.
  • Family history
    • Non-systematic heredity
    • In case of family context: increased monitoring
  • Ethnic background
    • Higher risk in melanodermia patients
    • Risk of Open angle primary glaucoma in Hispanic patients
    • Risk of Angle closure primary glaucoma in Asian patients.
  • Sudden trauma to the eye and complex surgeries.
  • Patients with severe myopia have a specific risk of glaucoma. (1)

Clinical Presentation

Video 4.2: Open angle glaucoma​

Characteristics

  • Characterised by an open irido-corneal angle.
  • The most common types of glaucoma.
  • Generally, involvement of both eyes.
  • Increased IOP in 2/3 of patients:
    • Ineffective drainage of the aqueous humour together with normal production.
  • Normal or low IOP in 1/3 of patients
    • Elevated incidence of vasospastic diseases in such patients. (1)

Video 4.3: Angle closure glaucoma

Characteristics

  • Characterised by a closed irido-corneal angle.
  • Caused by factors that induce obstruction of the irido-corneal angle by the iris:
    • Physical obstruction to drainage of the aqueous humour
    • Increased IOP
  • Primary angle closure glaucoma:
    • Acute, Intermittent or Chronic
  • Secondary angle closure glaucoma:
    • Proliferative diabetic retinopathy
    • Uveitis, Central Retinal Vein Occlusion, etc. (1)

Video 4.4: Visual symptoms​

Open angle glaucoma

  • Is asymptomatic for a long time
  • Progressive destruction of the visual field
  • Often starts with a time to recognition as the result of asymmetry of involvement and then loss of peripheral vision and at a more advanced stage, loss of central vision.
  • Can lead to blindness

Chronic angle closure glaucoma

  • Similar to the symptoms of open angle glaucoma.
  • Possible eye redness, discomfort, blurred vision or headache decreasing with sleep.

Acute angle closure glaucoma

  • Redness and severe eye pain
  • Decreased visual capacity
  • Seeing halos around lights
  • Nausea
  • Vomiting
  • Risk of blindness in absence of treatment (1)

Diagnostic

World Cells

Diagnostic approach

  • Chronic glaucoma:
    • Importance of early screening to minimise risk of blindness because the asymptomatic phase is long. (1)
  • Regular checks after age 40 years, in particular, in case of existence of risk factors. (4)

Additional examinations:

  • Measurement of visual acuity and investigation of the visual field to test peripheral vision
  • Examination of the appearance of the optic nerve with slit lamp examination(fundoscopy),
    • Utility of photographs for future comparison
  • Measurement of intraocular pressure with a tonometer.
  • Examination of the irido-corneal angle
    • Gonioscopy
      • Test performed with a small contact lens.
      • Demonstration of anterior peripheral synechiaes
    • Ultrasound
      • Measurement of the irido-corneal angle can be performed with a Lin25 or a Lin50 UBM probe.
  • Measurement of corneal thickness with a pachymeter.

Treatment

Eye Cells

Medical treatment

  • Is necessary to reduce intraocular pressure and to prevent irreversible lesions to the optic nerve.
  • Glaucoma cannot be cured:  it requires lifetime treatment
  • Use of eye drops (1)
    • Containing prostaglandins, beta-blockers or alpha-adrenergic agonists.
    • Objectives:
      • To reduce secretion of the aqueous humour
      • To promote its elimination.
    • Combinations are possible according to certain modalities.

Surgery

Trabeculectomy:

  • The oldest technique consisting of removing the trabeculum.
  • This procedure is generally well-tolerated.

Sclerotomy:

  • A more recent technique consisting of removing only part of the trabeculum.
  • Does not require opening of the eye.
  • Faster recovery of vision.
  • Cannot be used for all types of glaucoma.

Iridectomy

  • Removing part of the iris in order to enable better evacuation of the aqueous humour. 

Action on the trabeculum: Trabeculoplasty

  • A laser method of treatment of glaucoma consisting of delivering laser pulses to the trabeculum.
  • Produces contraction of the trabeculum enabling opening of the pathways of flow of the aqueous humour and consequently a decrease in intraocular pressure.
  • Two methods are available:
    • Argon laser trabeculoplasty (ALT)
      • Increasingly abandoned in favour of SLT
    • Selective trabeculoplasty (SLT)
      • More recent.
      • Advantage:
        • 100 times less power is delivered into the eye with equivalent efficacy,
        • So-called “cold” laser: does not produce any thermal lesion.
        • Painless.
        • Significantly reduces risk of complications.
        • Treatment in a single session.
      • Disadvantage: is not indicated for all types of glaucoma.

Action on the iris: Iridotomy

  • A small opening is made at the base of the iris with a laser, under local anaesthesia, to enable the aqueous humour to drain.
  • Can be done in the ophthalmologist’s office in only a few minutes.
  • Is reserved for certain types of chronic glaucoma.
  • Is performed for prevention to prevent the angle from completely closing. (4)

Action on the ciliary body: cyclo-photocoagulation or cyclo-collapse

  • Application of the diode laser to the ciliary body via the sclera opposite or by endocular approach.
  • Enables to decrease production of the aqueous humour and therefore to decrease IOP by partial destruction of the ciliary body.
  • Treatment generally is performed in the OR under local anaesthesia.
  • Is reserved primarily for refractory types of glaucoma. (4)

EMERGENCY

Initiation of emergency medical treatment that must be followed by laser iridotomy.

Laser treatment: Iridotomy

  • A small opening is made at the base of the iris, under local anaesthesia, to enable the aqueous humour to drain off.
  • Can be done in the ophthalmologist’s office in only a few minutes.
  • If this procedure is performed within 24 hours following the start of the acute episode, complete recovery is likely.

Surgical treatment: Iridotomy.

  • Removing part of the iris in order to enable better drainage of the aqueous humour.
  • If it does not produce a desired result, trabeculectomy can be considered. (4)

References

Cells
  1. Porter RS, Kaplan JL. Chapter 65. Glaucoma. The Merck Manual of Diagnosis & Therapy, 19th Edition,  Merck Research Laboratories 2011, p. 703-709.
  2. Organisation mondiale de la santé. Cécité et déficience visuelle. Aide-mémoire N°282  http://www.who.int/mediacentre/factsheets/fs282/fr/ . Août 2014
  3. Organisation mondiale de la santé. Prévention de la cécité et des déficiences visuelles.  Maladies oculaires prioritaires. Glaucome.  http://www.who.int/blindness/causes/priority/fr/index7.html
  4. Haute Autorité de Santé. Dépistage et diagnostic précoce du glaucome : problématique et perspectives en France. Novembre 2006