Primary Lens Luxation

Primary lens dislocation is the displacement of the lens from its usual position, either towards the anterior or posterior chamber of the eye, as a result of a mutation in the ADAMTS17 gene.

Symptoms

Clinical signs of primary lens dislocation appear at middle age, around 4 to 7 years of age. Symptoms common to this disorder include severe pain, tearing of the eye, decreased vision, clouding of the affected eye and redness. Displacement of the lens can cause an increase in intraocular pressure, which can lead to glaucoma. In some cases, lens dislocation may occur at the same time in both eyes.

Disease Management

Treatment of the disease will depend on whether the dislocation occurs in the anterior or posterior chamber, and on the presence of glaucoma. The main objective is to lower the ocular pressure and treat the underlying causes. In the case of anterior lens dislocation, surgical removal of the lens is used to try to save vision. Other options include glaucoma management, long-term use of eye drops for posterior chamber dislocations, or removal of the eyeball if there is pain.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Primary lens luxation is a condition in which the lens is displaced from its usual position, causing symptoms such as pain, loss of vision and even glaucoma. A mutation in the ADAMTS17 gene has been identified as a possible causative factor for this disease in dogs. The ADAMTS17 gene belongs to the ADAMTS gene family, which encodes metalloproteases, enzymes with a structural function in the lens fibers of the eye. In a study by Farias et al. (2010), a specific mutation was identified in the ADAMTS17 gene (c.1473+1G>A) that caused a frameshift and the introduction of a premature termination codon. This variant was found to be significantly associated with the development of primary lens luxation in three breeds of dogs analyzed in the study: Jack Russell Terrier, Miniature Bull Terrier and Lancashire Heeler. Subsequently, this same mutation was identified in dogs with primary lens luxation but from breeds other than those mentioned above.

Most affected breeds

  • Australian Cattle Dog
  • Border Collie
  • Chinese Crested Dog
  • Chinese Shar-Pei
  • German Hunting Terrier
  • Jack Russell Terrier
  • Lancashire heeler
  • Miniature Bull Terrier
  • Parson Russell Terrier
  • Patterdale Terrier
  • Portuguese Podengo
  • Rat Terrier
  • Sealyham Terrier
  • Tenterfield Terrier
  • Tibetan Terrier
  • Toy Fox Terrier
  • Volpino Italiano
  • Welsh Terrier
  • Wirehaired Fox Terrier
  • Yorkshire Terrier

Bibliography

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