ISSN 2398-2969      

Glaucoma

icanis

Introduction

  • Cause: glaucoma represents a group of heterogenous diseases which, in dogs, are characterized by pathologically elevated intraocular pressure resulting in retinal ganglion cell death.
  • Signs: ocular pain, blindness, episcleral congestion, conjunctival hyperemia, corneal edema, mydriasis.
  • Diagnosis: ophthalmic examination including gonioscopy and tonometry.
  • Treatment: ocular hypertensive medications and surgical options.
  • Prognosis: guarded.
    Print off the owner factsheet on Glaucoma Glaucoma to give to your client.

Pathogenesis

Etiology

Predisposing factors

General

  • Breeds predisposed to primary closed angle and lens angle glaucoma.
  • Breeds predisposed to primary lens luxation.

Specific

  • Presence of goniodysgenesis.
  • Homozygosity for known mutations for primary open angle glaucoma and primary lens luxation.
  • Uveitis.
  • Cataracts Cataract.
  • Previous intraocular surgery.
  • Intraocular hemorrhage.
  • Ocular melanosis.

Pathophysiology

  • See also Glaucoma: secondary to anterior uveitis Glaucoma: secondary to anterior uveitis , Glaucoma: due to lens luxation Glaucoma: due to lens luxation , Glaucoma: primary closed angle Glaucoma: primary closed angle and Glaucoma: primary open angle Glaucoma: primary open angle.
  • Normal intraocular pressure is a balance between aqueous humor production and outflow:
    • Aqueous humor is produced by the ciliary body processes by active secretion (mainly) and ultrafiltration.
    • Aqueous humor then traverses the posterior chamber via the pupil into the anterior chamber.
    • From the anterior chamber, the majority of aqueous drains via the iridocorneal angle.
    • The main components of this angle are the pectinate ligament and ciliary cleft which contains the sieve-like trabecular meshwork.
    • The majority of aqueous (~85%) filters through these structures and enters the angular aqueous plexus before entering the scleral venous plexus ('conventional' outflow).
    • A minority of aqueous (~15%) bypasses the aqueous plexus and reaches the scleral venous plexus via the choroid and suprachoroidal space.
    • Normal intraocular pressure in the dog is 10-25 mm Hg.
  • In dogs, the only consistent risk factor for glaucoma amongst the group of heterogenous diseases is pathologically elevated intraocular pressure.
  • Overproduction of aqueous humor is not a recognized phenomenon in dogs and, thus, all known forms of glaucoma relate to obstruction to aqueous humor outflow.
  • Aqueous humor obstruction can occur at any point from its release into the posterior chamber to its ultimate drainage into the angular aqueous plexus and include the following:
    • Pupil block:
      • Iris bombe. Peripheral synechiae (adhesions between posterior iris and anterior lens capsule) for 360° in chronic uveitis.
      • Lens luxation and subluxation.
      • Vitreous prolapse (following lens removal or lens luxation).
    • Obstruction of entrance to iridocorneal angle:
      • Severe goniodysgenesis (pectinate ligament dysplasia) in primary closed angle glaucoma.
      • Obstruction by red blood cells (trauma), white blood cells and inflammatory debris (acute and chronic uveitis).
      • Anterior synechiae (chronic uveitis).
    • Obstruction within ciliary cleft:
      • Severe goniodysgenesis in primary closed angle glaucoma.
      • Undefined anatomical and biochemical changes in primary open angle glaucoma.
      • Collapse of ciliary cleft in all forms of glaucoma.
      • Neoplastic extension.
      • Obstruction by red blood cells (trauma), white blood cells and inflammatory debris (acute and chronic uveitis).
  • Elevation of intraocular pressure causes interruption of vacular supply to optic nerve head and axoplasmic flow within optic nerve axons.
  • Increase in glutamate levels may cause excitotoxicity-mediated retinal ganglion cell death.

Timecourse

  • Variable dependent on cause.
  • Acute in primary closed angle glaucoma and primary lens luxation.
  • Chronic in anterior uveitis, neoplasia and ocular melanosis Eye: ocular melanosis and secondary glaucoma - Cairn terrier.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

Other sources of information

Related Images

OWNER FACTSHEETS

Glaucoma

Want more related items, why not
contact us

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code