Lens luxation

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A 5-year-old Fox Terrier with primary lens luxation[1]

Primary lens luxation (PLL; ectopia lentis) is an polygenic ocular disease characterized by dislocation of the lens from the supporting ciliary zonule fibres.

Secondary lens luxation may be observed secondary to severe trauma or intraocular disease and is not considered a primary condition.

Primary lens luxation has been reported in the Miniature Bull terrier, Lancashire Heeler, Shar Pei[2], Chinese Crested, Volpino Italiano, Border Collie, Jack Russell Terrier and other terrier breeds. This disease is similar to the human disease Weill-Marchesani syndrome[3].

This disease is caused by an ADAMTS17 mutation in the canine chromosome 3[4][5] and leads to zonular degeneration.

PLL involves lens displacement from its normal position within the patellar fossa to the anterior or posterior chambers due to rupture of the lens zonules. Subsequent to luxation, the lens can induce secondary glaucoma and anterior uveitis.

This disease is usually bilateral in dogs, although both lenses do not luxation simultaneously and may be separated by weeks or months[6].

Affected dogs are often middle-aged and present with lens luxation on fundoscopic examination. Affected dogs may develop ocular hypertension and secondary glaucoma[7], anterior uveitis, Descemet's membrane duplication[8], retinal detachment or retinal degeneration and constitutes and ocular emergency with these cases.

Diagnosis is usually confirmatory on identification of the ADAMTS17 mutation by DNA testing[9].

A differential diagnosis would include other causes of lens luxation.

Testing of affected breeding stock and sterilization of affected dogs may minimizes incidence of this disease.

Conservative medical treatment is usually initiated in the short-term with use of miotic drugs (e.g. 0.005% latanaprost)[10], as topically drugs may delay further anterior luxation of an unstable lens.

A bilateral lensectomy (intracapsular lens extractions) or lenticular phacoemulsification is usually required as a salvage procedure, but in valuable dogs, a sulcus intraocular lens implant is usually applied[11][12].

References

  1. Grahn BH et al (2003) Diagnostic ophthalmology. Congenital lens luxation and secondary glaucoma. Can Vet J 44(5):427
  2. Lazarus JA et al (1998) Primary lens luxation in the Chinese Shar Pei: clinical and hereditary characteristics. Vet Ophthalmol 1(2-3):101-107
  3. Farias FH et al (2010) An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Invest Ophthalmol Vis Sci 51(9):4716-4721
  4. Gould D et al (2011) ADAMTS17 mutation associated with primary lens luxation is widespread among breeds. Vet Ophthalmol 14(6):378-384
  5. Sargan DR et al (2007) Mapping the mutation causing lens luxation in several terrier breeds. J Hered 98(5):534-538
  6. Davidson MG & Nelms SR (2007) Diseases of the canine lens and cataract formation. In: Veterinary Ophthalmology (ed. Gelatt K). Blackwell Publishing, Ames. pp859–887
  7. Johnsen DA et al (2006) Evaluation of risk factors for development of secondary glaucoma in dogs: 156 cases (1999-2004). J Am Vet Med Assoc 229(8):1270-1274
  8. Kafarnik C et al (2009) Canine duplication of Descemet's membrane. Vet Pathol 46(3):464-473
  9. Oberbauer AM et al (2008) Inheritance of cataracts and primary lens luxation in Jack Russell Terriers. Am J Vet Res 69(2):222-227
  10. Binder DR et al (2007) Outcomes of nonsurgical management and efficacy of demecarium bromide treatment for primary lens instability in dogs: 34 cases (1990-2004). J Am Vet Med Assoc 231(1):89-93
  11. Stuhr CM et al (2009) Intracapsular lensectomy and sulcus intraocular lens fixation in dogs with primary lens luxation or subluxation. Vet Ophthalmol 12(6):357-360
  12. Wilkie DA et al (2008) A modified ab externo approach for suture fixation of an intraocular lens implant in the dog. Vet Ophthalmol 11(1):43-48