Contributors: Dennis E Brooks, David L Williams, David Gould

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Cause: a recessively inherited condition mostly affecting terrier breeds.
  • Secondary lens luxation is uncommon but may occur secondary to buphthalmos (due to chronic glaucoma.
  • Primary glaucoma is ultimately bilateral, but initially presents with acute unilateral signs. Lens may luxate anteriorly into the anterior chamber (anterior lens luxation) or posteriorly into the vitreous (posterior lens luxation).
  • Signs: anterior luxation leads to signs of secondary glaucoma. Posterior luxation is more 'silent' in presentation - reduced vision may be only sign.
  • Diagnosis: ophthalmic examination to identify abnormally positioned lens.
  • Treatment: surgical lensectomy for anterior luxation. Enucleation if irreversible glaucoma and blindness. Posterior luxation may be conservatively managed.
  • Prognosis: fair to good as long as identified and treated promptly. Poor visual prognosis if any delay in diagnosis and treatment. Successful lensectomy will allow return of vision as long as the secondary glaucoma has not caused irreversible blindness. However, vision will be hyperopic (long-sighted) following lens removal.

    Print off the owner factsheet on Lens luxation Lens luxation to give to your client.

Presenting Signs

Anterior lens luxation

  • Sudden onset unilateral blindness, corneal edema, episcleral reddening, ocular pain.
  • Pupil on affected side usually dilated.
  • Penlight examination will identify abnormally positioned lens in the anterior chamber, or pushing the iris anteriorly to cause 'pupil block'.
  • Contraleral eye will show signs of lens subluxation: deepened anterior chamber (loss of iris support by the lens), iridodonesis ('iris wobble' during eye movements), phacodonesis ('lens wobble'), vitreal herniation through the pupil, aphakic crescent if pupil is dilated Eye: anterior lens luxation - Parson Russell terrier.

Posterior lens luxation

  • Owner may notice signs of reduced vision.
  • Intraocular examination will identify the abnormally positioned lens in the posterior segment, a deep anterior chamber, irododonesis.

Age Predisposition

  • 3-8 years old (peak at 4-5 years old).

Breed Predisposition

Cost Considerations

  • Surgical treatment is expensive, and bilateral lensectomy surgery may be required.
  • Enucleation Eye: enucleation of a blind, painful eye with glaucoma may be necessary.



  • Recessively inherited.
  • A specific mutation in the ADAMTS17 gene is responible for lens luxation in most affected breeds. A genetic test is avilable to identify affected and carrier dogs.
  • However, in some breeds (including Shar pei, Bassett Griffon Vendeen, Brittany spaniel) the condition is due to a different mutation Genetic tests for hereditary eye diseases.

Predisposing Factors


  • Breed-related, especially terrier breeds.


  • Dogs homozygous for the ADAMTS17 mutation.


  • ADAMST17 mutation leads to progressive breakdown of lens zonule attachments, resultant lens instability and eventually complete lens luxation.
  • Anterior movement of the lens leads to pupil block as the lens pushes anteriorly against the posterior lens and blocks movement of aqueous humour from the posterior to anterior chamber, leading to secondary glaucoma. Alternatively, the lens may pass through the pupil to enter the anterior chamber, also leading to secondary glaucoma.
  • Posterior luxation results in the lens entering the vitreous.

Primary luxation

  • Abnormal lens zonule (bizarre reticulate zonular fiber formations between posterior wall of lens and ciliary processes) → disrupted lens attachment → lens luxation→ increased intra-ocular pressure if lens moves into anterior chamber causing pupillary block.

Secondary luxation

Either Glaucoma: buphthalmos (even mild) → ruptures lens zonule.
Or Cataract: increased lens size → stress on lens zonular fibers.
  • → subluxation Traumatic rupture of zonule (if ventral zonular fibers still attached) → maybe complete luxation.


  • Progressive lens zonule breakdown throughout life, but acute presentation usually in young/middle-aged dogs.


Presenting Problems

  • Sudden onset red eye, cloudy eye, painful eye, blindness.

Client History

  • Painful eye.
  • Red eye.
  • Corneal clouding.

Clinical Signs

  • Glaucoma - blindness, corneal edema, episcleral congestion (initially unilateral).
  • Aphakic crescent if lens if subluxated.
  • Iridodonesis - iris 'wobble' with eye movements because lens no longer supports iris.
  • Vitreal strands in anterior chamber.
  • Lens visible in anterior chamber.
  • Deep anterior chamber if posterior luxation.

Diagnostic Investigation

  • The key diagnostic step involves determining if the luxation is primary or secondary:
    • Primary: breeds predisposed to lens luxation, eyes normal size, usually bilateral signs.
    • Secondary: breeds predisposed to glaucoma, eye enlarged, usually unilateral signs.

Differential Diagnosis


Initial Symptomatic Treatment

  • Reduce intraocular pressure:
    • Mannitol Mannitol infusion (contra-indications: cardiac disease, renal disease, hypovolemia).
    • Topical carbonic anhydrase inhibitors (brinzolamide, dorzolamide Dorzolamide ).
  • Analgesia.

Standard Treatment

Surgical treatment

  • Anterior luxation:
    • Surgical - lensectomy Lendectomy.
    • Enucleation in blind eyes with intractable glaucoma.
  • Posterior luxation:
    • Regular monitoring or long-term medical treatment with the use of topical miotic drugs (eg travoprost or latanoprost Latanoprost twice daily) to constrict the pupil in an attempt to keep the lens in the posterior segment.

      Avoid miotic drugs if there is significant vitreal herniation through the pupil into the anterior chamber, or if secondary uveitis is present. Miotics are contra-indicated in anterior lens luxation.


  • Frequent monitoring (eg weekly) immediately following surgery or following instigation of medical treatment:
    • Signs of uveitis, retinal detachment, glaucoma.
    • Measure intraocular pressure Tonometry.



  • Good prognosis for saving vision following lensectomy in early cases of primary lens luxation, although following lensectomy, aphakic eyes remain severely hyperopic (long-sighted).
  • Guarded prognosis if any delay in diagnosis and treatment.

Expected Response to Treatment

Reasons for Treatment Failure

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gould D J, Petitt L, McLaughlin B, Holmes N, Forman O, Thomas A, Ahonen S, Lohi H, O'Leary C, Sargan D, Mellersh C (2011) ADAMTS17 mutation associated with primary lens luxation is widespread among breeds. Vet Ophthalmol 14 (6), 378-384 PubMed.
  • Farias F H, Johnson G S, Taylor J F, Guiliano E, Katz M L, Sanders D N, Schnabel R D, McKay S D, Khan S, Gharahkhani P, O'Leary C A, Pettitt L, Forman O P, Boursnell M, McLaughlin B, Ahonen S, Lohi H, Hernandez-Merino E, Gould D J, Sargan D R, Mellersh C (2010) An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Investigative Ophthalmology & Visual Sciences 51 (9), 4716-4721 PubMed.
  • Sargan D R, Withers D, Pettitt L, Squire M, Gould D J, Mellersh (2007) Mapping the mutation causing lens luxation in several terrier breeds. J Hered 98 (5), 534-538 PubMed.

Other sources of information

Other Sources of Information