Contributors: Dennis E Brooks, David L Williams, James Oliver
Species: Feline | Classification: Diseases
Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading
Introduction
- 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
- Siamese Siamese predisposed.
Pathogenesis
Etiology
- 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.
- Congenital:
- Secondary luxation:
- Uveitis Anterior uvea: traumatic uveitis.
- Glaucoma.
- Trauma.
- Cataract Cataract.
- Neoplasia.
Predisposing Factors
General
- Pre-existing intraocular disease:
- Uveitis Uveitis: viral.
- Glaucoma Glaucoma.
Pathophysiology
- 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.
- Corneal edema:
- Retinal detachment Retina: detachment is another common long-term complication following lens luxation.
Diagnosis
Presenting Problems
- Corneal clouding.
- Ocular discomfort (often minimal in cat).
Clinical Signs
- 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.
Diagnostic Investigation
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.
- If posterior segment cannot be visualized:
- Electroretinogram:
- If retinal function in doubt.
Differential Diagnosis
- Uveitis.
- Glaucoma Glaucoma.
- Corneal ulcer Eye: corneal ulcer.
- Neoplasia.
- Corneal endothelial dystrophy.
- Microphakia/lens coloboma.
Treatment
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:
- 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.
Monitoring
- Intraocular pressure (IOP)
- Secondary glaucoma common.
- Signs of uveitis.
- Lens position:
- If lens luxation is posterior.
- Contralateral eye.
Outcomes
Prognosis
- 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
Publications
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.