Canis ISSN: 2398-2942

Glaucoma: due to lens luxation

Contributor(s): David L Williams, James Oliver

Introduction

  • Cause: anterior dislocation of lens from patellar fossa impairs flow and drainage of aqueous humor within and from the eye. Results in pathologically elevated intraocular pressure.
  • Signs: abnormal lens position, ocular pain, corneal edema, episcleral congestions, vision loss.
  • Diagnosis: ophthalmic examination and tonometry.
  • Treatment: removal of lens from anterior chamber, antiglaucoma medications.
  • Prognosis: guarded.

Pathogenesis

Etiology

Predisposing factors

General
  • Breed.
  • Trauma.
  • Intraocular inflammation.

Specific

  • Homozygosity for known mutation.

Pathophysiology

  • In primary lens luxation there is progressive weakening and breakdown of the zonular fibers which hold the lens in place.
  • Zonular breakdown may also result from chronic inflammation Eye: anterior lens luxation - German Shepherd dog , chronic cataract Eye: anterior lens luxation - Miniature Poodle , trauma Eye: anterior lens luxation - Labrador Retriever or neoplastic expansion within the globe.
  • Anterior displacement of the lens results in 'pupillary block'. The lens and vitreous which follows it impedes the circulation of aqueous humor from the posterior to anterior chamber.
  • Build-up of aqueous behind the iris displaces it anteriorly leading to collapse of the iridocorneal angle and eventual development of anterior synechiae

Timecourse

  • Weakening and breakdown of lens zonules occurs over years.
  • Early lens luxation may be detected by presence of aphakic crescent, lens or iris trembling (phacodonesis or iridodonesis) or presence of vitreous within anterior chamber.

Epidemiology

  • Breed predisposition.

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.
  • Gould D et al (2011) ADAMTS17 mutation associated with primary lens luxation is widespread among breeds. Vet Ophthalmol 14 (6), 378-384 PubMed.
  • Farias F H et al (2010) An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Invest Ophthalmol Vis Sci 51 (9), 4716-4721 PubMed.

Other sources of information


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