Canis ISSN: 2398-2942

Lens: congenital primary cataract

Contributor(s): Dennis E Brooks, David L Williams

Introduction

  • A cataract is an opacification of the lens.
  • May be primary (breed-related) or secondary due to disease (uveitis, diabetes, PRA).
  • Developmentally staged as incipient, immature (tapetal reflex present), mature (no tapetal reflex/blindness) and hypermature (wrinkled lens capsule).
  • Either congenital, eg Miniature Schnauzer, Boston Terrier, Welsh Springer Spaniel, at early age, eg Afghan Hound, German Shepherd dog or at later stage, eg Standard Poodle.
  • Usually inherited (autosomal recessive).
  • Inherited as incomplete dominant in Labrador Retriever, Golden Retriever (posterior subcapsular opacity).
  • Good prognosis if phacoemulsification performed and if no other ocular structures involved.
  • Early developing cataract: remove at an early stage either by irrigation, aspiration, extracapsular extraction or phacoemulsification → prevents lens-induced uveitis.

Pathogenesis

Etiology

  • Genetic defects.
  • Secondary to uveitis, involving changes such as:
    • Posterior synechiae.
    • Altered aqueous humor in uveitis.
  • Radiation.
  • Diabetes mellitus Diabetes mellitus.
  • Hypocalcemia Primary maternal dystocia.
  • Senile cataracts.
  • Degenerating retina (PRA).
  • Nutritional (milk replacers).

Predisposing factors

General
  • Breeds at risk.
  • Old age.

Pathophysiology

  • Lens opacification is termed a cataract.
  • Cross-linking of lens proteins causes lens opacification.

Timecourse

  • Incipient cataracts can progress to immature, mature and hypermature stages, although these stages are not mutually exclusive.
  • Nuclear cataracts may become relatively smaller with time as the lens cortex grows in size.
  • Cortical cataracts almost always progress.

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.
  • Williams D L, Boydell I P & Long R D (1996) Current concepts in the management of canine cataract: a survey of techniques used by surgeons in Britain, Europe and the USA and a review of recent literature. Vet Rec 138 (15), 347-53 PubMed.

Other sources of information

  • Gelatt K N (1998) Veterinary Ophthalmology. 3rd edn. Williams & Wilkins.


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