Eye: lens luxation

• 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.

• Lens in anterior chamber.

• Corneal opacity.

• Most common in cats aged 7-9 years.

• Siamese Siamese predisposed.

• 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:
  • Uveitis Anterior uvea: traumatic uveitis.
  • Glaucoma.
  • Trauma.
  • Cataract Cataract.
  • Neoplasia.

General

• Pre-existing intraocular disease:
  • Uveitis Uveitis: viral.
  • Glaucoma Glaucoma. 

• 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.

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

• Usually unilateral, may be bilateral.
• Lens visible in anterior chamber anterior luxation    .
• 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.

Other

• 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.

• Uveitis.
• Glaucoma Glaucoma.
• Corneal ulcer Eye: corneal ulcer.
• Neoplasia.
• Corneal endothelial dystrophy.
• Microphakia/lens coloboma.

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:
  • Topical corticosteroids or NSAIDs.
  • Systemic NSAIDs Therapeutics: eye.

Surgical treatment

• Enucleation Eye: enucleation should be performed in blind, painful eyes with intractable glaucoma.
• Intracapsular lens extraction Lendectomy or phacoemulsification Phacoemulsification for visual or potentially visual eyes.

• 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.

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

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 1 (4), 239-244 VetMedResource.