Canis ISSN: 2398-2942

Glaucoma: primary open angle

Synonym(s): POAG

Contributor(s): David L Williams, James Oliver

Introduction

  • Cause: inherited abnormality in aqueous humor outflow pathways which cannot be visualized by routine examination techniques.
  • Signs: often insidious and chronic in onset. Bilateral globe enlargement, lens subluxation, visual deficits, corneal changes, raised intraocular pressure.
  • Diagnosis: ophthalmic examination, gonioscopy, tonometry.
  • Treatment: topical ophthalmic antiglaucoma medications.
  • Prognosis: guarded.

Pathogenesis

Etiology

  • Results from abnormalities of the extracellular matrix (ECM) changes in the aqueous humor outflow pathways and abnormal function of trabecular cells.
  • The ECM provides resistance to aqueous humor outflow and this becomes pathological in primary open angle glaucoma and intraocular pressure gradually rises.
  • In Beagles with POAG, reported changes to ECM constituents include reduction in hyaluronic acid and chondroitin sulphate and the presence of an undegradable glycosaminoglycan-like material.
  • In Beagles, it has been suggested that fibrillin in particular may be a major component of resistance for aqueous humor to traverse the trabecular meshwork.
  • As intraocular pressure rises, chronic changes of globe enlargement (buphthalmos) and lens subluxation occur.
  • To date, two separate mutations in ADAMTS10 have been found to be causative of primary open angle glaucoma in the Beagle and Norwegian Elkhound.
  • All affected dogs are homozygous for the respective mutations.

Predisposing factors

General

  • Breed.

Specific

  • Homozygosity for known causative mutations.

Timecourse

  • Insidious in onset.
  • As elevated intraocular pressure becomes long standing, chronic changes become noticeable.

Epidemiology

  • Relates to breed distribution within a given population.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Ahonen S J et al (2014) A Novel Missense Mutation in ADAMTS10 in Norwegian Elkhound Primary Glaucoma. PLoS One (11), e111941 PubMed.
  • Kuchtey J et al (2013) Screening ADAMTS10 in dog populations supports Gly661Arg as the glaucoma-causing variant in beagles. Invest Ophthalmol Vis Sci 54 (3), 1881-1886 PubMed.
  • Kuchtey J et al (2011) Mapping of the disease locus and identification of ADAMTS10 as a candidate gene in a canine model of primary open angle glaucoma. PLoS Genet (2), e1001306 PubMed.
  • Samuelson D A, Gum G G & Gelatt K N (1989) Ultrastructural changes in the aqueous outflow apparatus of beagles with inherited glaucoma. Invest Ophthalmol Vis Sci 30 (3), 550-561 PubMed.

Other sources of information


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