Contributors: Dennis E Brooks, David L Williams, James Oliver

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Cause: lens luxation occurs when there is breakdown of the supporting lens zonules.
  • In cats, lens luxation usually occurs secondary to other intraocular disease, in particular uveitis.
  • Anterior lens luxation is associated with corneal damage and secondary glaucoma.
  • Diagnosis: gross ocular and ophthalmoscopic examination should reveal above signs.
  • Treatment: surgical lens extraction and treatment of other intraocular disease.
  • Emergency treatment is rarely required (in contrast to dog).
  • Prognosis: fair if treatment prompt and any other intraocular disease adequately controlled.

Presenting Signs

  • Lens in anterior chamber.
  • Corneal opacity.

Age Predisposition

  • Most common in cats aged 7-9 years.

Breed Predisposition



  • Primary luxation:
    • Congenital:
      • May be associated with microphakia.
    • Hereditary
      • Inheritance as a dominant trait possibly as a result of mutation in the FBN1 gene has been reported.
  • Secondary luxation:

Predisposing Factors



  • Lens luxation occurs when there is complete 360° breakdown of the lens zonules.
  • Subluxation occurs when there is incomplete breakdown of the lens zonules.
  • Breakdown of lens zonules may be a result of:
    • Congenital or inherited weakness.
    • Inflammatory damage.
    • Globe stretching (glaucoma).
    • External trauma.
    • Cataract (increased lens weight).
    • Damage from intraocular neoplasia.
  • The lens may luxate anteriorly into the anterior chamber or posteriorly into the vitreous.
  • Anterior lens luxation is most common and leads to further complications:
    • Corneal edema:
      • Owing to direct damage to corneal endothelium and compromise of pump mechanism responsible for keeping cornea relatively dehydrated and clear.
    • Secondary glaucoma:
      • Pupillary block from presence of lens and/or vitreous within pupil.
      • Compromise of aqueous outflow via iridocorneal angle.
  • Retinal detachment Retina: detachment is another common long-term complication following lens luxation.


Presenting Problems

  • Corneal clouding.
  • Ocular discomfort (often minimal in cat).

Clinical Signs

  • Usually unilateral, may be bilateral.
  • Lens visible in anterior chamber anterior luxation Lens: anterior luxation 01  Lens: anterior luxation 02 .
  • Iridodenesis (iris trembling).
  • Corneal edema.
  • Aphakic crescent.
  • Deep anterior chamber.
  • Ocular pain (variable).
  • Visual deficits (variable).
  • Signs of anterior uveitis Anterior uvea: traumatic uveitis:
    • Keratic precipitates (deposits of cells and inflammatory debris on corneal endothelium).
    • Iridal neovascularization.
    • Fibrin or pus within anterior chamber.

Diagnostic Investigation


  • Tonometry  Tonometry  (meaurement of intraocular pressure (IOP)):
    • Normal range 15-25 mmHg.
    • Reduced in anterior uveitis.
    • Elevated in glaucoma.
    • Compare with contralateral eye.
  • Ocular ultrasound  Ultrasonography: eye  :
    • If posterior segment cannot be visualized:
      • Rule out retinal detachment and intraocular neoplasia.
  • Electroretinogram:
    • If retinal function in doubt.

Differential Diagnosis


Initial Symptomatic Treatment

Medical treatment

  • Topical antiglaucoma medications:
    • Carbonic anhydrase inhibitors, eg dorzolamide Dorzolamide  or brinzolamide TID.
    • Beta-blockers, eg timolol Timolol BID-TID.
      Potential cardiorespiratory side effects.
  • Anti-inflammatories if uveitis present:

Surgical treatment


  • Intraocular pressure (IOP)
    • Secondary glaucoma common.
  • Signs of uveitis.
  • Lens position:
    • If lens luxation is posterior.
    • Contralateral eye.



  • Fair if treatment prompt and any other intraocular disease adequately controlled.

Expected Response to Treatment

Reasons for Treatment Failure

  • Inability to control uveitis.
  • Secondary glaucoma.
  • Retinal detachment.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Maggs D J (2009) Feline uveitis. An 'intraocular lymphadenopathy'. J Feline Med Surg 11 (3), 167-182 PubMed.
  • Townsend W M (2008) Canine and feline uveitis. Vet Clin North Am Small Anim Pract 38 (2), 323-346 PubMed.
  • Payen G, Hänninen R L, Mazzucchelli S et al (2005) Primary lens instability in ten related cats: clinical and genetic considerations. JSAP 52 (8), 402-410 PubMed.
  • Sansom J (2000) Diseases involving the anterior chamber of the dog and cat. In Practice 22 (2), 58-70 VetMedResource.
  • Molleda J M, Martín E, Ginel P J et al (1995) Microphakia associated with lens luxation in the cat. JAAHA 31 (3), 209-212 PubMed.
  • Olivero D K, Riis R C, Dutton A G et al (1991) Feline lens displacement - a retrospective analysis of 345 cases. Prog Vet Comp Ophthalmol (4), 239-244 VetMedResource.

Other Sources of Information