ISSN 2398-2969      

Lens: hereditary primary cataract

icanis

Introduction

  • Cataract is an opacity in the lens, primary cataract occurs in the absence of any other ocular disease has a bilateral potential and is hereditary. Secondary cataract occurs as a sequela to other trauma, ocular disease, eg progressive retinal atrophy.
  • Cause: usually autosomal recessive inheritance, possibly dominant with incomplete penetrance in some Retriever breeds.
  • Signs: lens opacity, may be focal or diffuse - appearance usually characteristic for the particular breed. May be progressive or stationary. May be congenital in some breeds, often associated with microphthalmos.
  • Diagnosis: lens opacity seen by distant direct ophthalmoscopy, direct ophthalmoscopy or slit-lamp biomicroscopy gives better resolution.
  • Treatment: lendectomy by phacoemulsification (before cataract matures or uveitis is present). Earlier extraction → prevents lens-induced uveitis.
  • Prognosis: reasonable if phacoemulsification and no other ocular abnormalities, many post-operative complications possible.

Pathogenesis

Etiology

  • Hereditary. Usually autosomal recessive, but may be dominant with incomplete penetrance. Hereditary pattern in some breeds still undetermined.

Predisposing factors

General
  • Environmental factors may play a part, especially with congenital cataracts associated with microphthalmos.

Pathophysiology

  • Hereditary cataracts follow a characteristic pattern for the breed.
  • Opacities are caused by metabolic and/or anatomical disturbances to normal lens structure and function.
  • Lens crystallines are altered during cataract formation and are accompanied by morphologic changes in lens capsule, anterior lens epithelium and lens fibers.
  • Cataracts may be classified according to: stage of development (incipient, immature, mature, hypermature); age of animal (congenital, developmental, senile); or position of cataract (nuclear, cortical, equatorial, capsular, subcapsular).
  • Normal lens is maintained in dehydrated state, depends on energy from lens epithelium and lens fibers.
  • In cataractous lens, hydration of the fibers occurs impairing transmission of light.
  • Lens fibers become swollen resulting in fiber membrane rupture, cytoplasmic extrusion and lens cell death.
  • Vacuoles often present in equatorial region, imply progression likely - represent focal cell death, protein and lipid aggregation.
  • Lens opacification is due to hydration and lens fiber loss.
Congenital with microphthalmos
  • Miniature Schnauzer Schnauzer: miniature : mainly nuclear, sometimes cortical, rarely progressive. Some have posterior lenticonus and microphakia.
Early-onset and progressive
  • Boston Terrier Boston Terrier , Miniature Schnauzer Schnauzer: miniature , Staffordshire Bull Terrier Staffordshire Bull Terrier : bilateral, spreads from nucleus and suture lines Cataract primary hereditary non-congenital - Boston Terrier 8 weeks , leads to total cataract Cataract primary hereditary non-congenital - Boston Terrier 3 years. Starts at 8-10 weeks.
  • Cavalier King Charles Spaniel Cavalier King Charles Spaniel : progressive, bilateral and symmetrical. Becomes total in young adult. These affect the suture lines, are typically triangular at the confluence of the lines, may be inverted Y-shaped or pyramidal.
  • Chesapeake Bay Retriever Retriever: Chesapeake Bay : posterior polar cataract, may involve suture lines and equatorial area of lens as well. May progress.
  • Golden Retriever Retriever: Golden , Labrador Retriever Retriever: Labrador : posterior subcapsular polar cataract at confluence of suture lines Cataract primary hereditary non-congenital - Golden Retriever. Second form is progressive to total - may be due to same gene, showing variable penetrance.
  • Siberian Husky: inverted Y-shape.
Other forms of cataract
  • American Cocker Spaniel American Cocker Spaniel : pleomorphic cataract, non-symmetrical, stationary or progressive Cataract primary hereditary non-congenital - American Cocker Spaniel. Onset 2 months-6 years.
  • German Shepherd Dog German Shepherd Dog : bilateral, slowly progressive Cataract primary hereditary non-congenital - GSD 9 months. Starts as vacuoles at suture lines at 8 weeks Cataract primary hereditary non-congenital - GSD 4 months.
  • Old English Sheepdog Old English Sheepdog : bilateral, asymmetrical, progressive. Starts at 7 months-2 years.
  • Toy Poodle: Toy , Miniature Poodle: miniature and Standard Poodle Poodle: Standard : bilateral, symmetrical, progressive, cortical Cataract primary hereditary non-congenital - Standard Poodle 12 months. Starts from 5 months.
  • Welsh Springer Spaniel: bilateral, symmetrical, progressive nuclear and cortical vacuolation Cataract primary hereditary non-congenital - Welsh Springer Spaniel 8 weeks. Starts from 8 weeks.
Posterior polar subcapsular
  • Boston Terrier Boston Terrier : late onset, from 3-10 years. Subcapsular, anterior radial wedges from equator.
  • Norwegian Elkhound Elkhound : posterior polar cataract with extensions around suture lines, may involve anterior cortex Cataract primary hereditary non-congenital - Norwegian Buhund. Onset 3-4 months.

Timecourse

  • Progression typical for the breed.
  • Equatorial vacuoles imply progression likely.

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), 347-353 PubMed.
  • Curtis R & Barnett K C (1989) A survey of cataracts in Golden and Labrador Retrievers. JSAP 30 (5), 277-286 VetMedResource.
  • Barnett K C (1988) Inherited eye disease in the dog and cat. JSAP 29 (7), 462-75 VetMedResource.
  • Strande A, Nicolaissen B & Bjerkas I (1988) Persistent pupillary membrane and congenital cataract in a litter of English Cocker Spaniels. JSAP 29 (4), 257-60 VetMedResource.
  • Barnett K C (1986) Hereditary caract in the German Shepherd Dog. JSAP 27 (6), 387-95 VetMedResource.
  • Barnett K C (1985) The diagnosis and differential diagnosis of cataract in the dog. JSAP 26 (6), 305-16 VetMedResource.
  • Barnett K C & Startup F G (1985) Hereditary cataract in the Standard Poodle. Vet Rec 117 (1), 15-6 PubMed.
  • Curtis R (1984) Late-onset cataract in the Boston Terrier. Vet Rec 115 (22), 577-8 PubMed.
  • Narfström K & Dubielzig R (1984) Posterior lenticonus, cataracts and microphthalmia: congenital ocular defects in the Cavalier King Charles Spaniel. JSAP 25 (11), 669-77 Wiley Online Library.
  • Narfström K (1981) Cataract in the West Highland White Terrier. JSAP 22 (7), 467-71 PubMed.
  • Barnett KC (1980) Hereditary cataract in the Welsh Springer Spaniel. JSAP 21 (11), 621-5 PubMed.
  • Barrie K P, Peiffer R L, Gelatt K N & Williams L W (1979) Posterior Ienticonus, microphthalmia, congential cataracts and retinal folds in an Old English Sheepdog. JAVMA 15, 715 AGRIS FAO.
  • Gelatt K N et al (1979) Cataracts in Chesapeake Bay Retreivers. JAVMA 175 (11), 1176-8 PubMed.
  • Barnett K C (1978) Hereditary cataract in the dog. JSAP 19 (2), 109-20 PubMed.
  • Yakely W L (1978) A study of heritability of cataracts in the American Cocker Spaniel. JAVMA 172 (7), 814-17 VetMedResource.
  • Olesen H P, Jensen O A & Norn M S (1974) Congenital hereditary cataract in Cocker Spaniels. JSAP 15 (12), 741-50 PubMed.

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