Lens Luxation

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Issues

Lens Luxation

 

  • Total dislocation of the lens from its normal location.
  • Anterior—forward displacement through the pupil into the anterior chamber.
  • Posterior—backward displacement into the vitreous.
  • Occurs when the lens capsule separates 360° from the zonules that hold the lens in place.
  • Subluxation—partial separation of the lens from its zonular attachments; the lens remains in a normal or near-normal position in the pupil.
  • Primary (hereditary) luxation—due to a gradual zonular breakdown; usually inherited in dogs; often bilateral.
  • Congenital luxation—often associated with other congenital anomalies.
  • Secondary luxation—due to chronic inflammation, buphthalmia, intraocular neoplasia, senile zonular degeneration or trauma.

 

SIGNALMENT

  • Primary—usually seen in adult dog (typically 3–8 years old); commonly affected breeds include terriers, Chinese crested and Shar-Pei; rare in cats.
  • Secondary—dog and cat; any age/breed.

 

SIGNS

  • Lens instability and subluxation—fibrils of liquefied vitreous in the anterior chamber; abnormally shallow or deep anterior chamber; abnormal iris curvature; phacodenesis (tremor of the lens with globe movement); iridonesis (tremor of the iris with globe movement); aphakic crescent (crescent-shaped area of the pupil that is lacking the lens).
  • Lens luxation—anterior when the lens is in the anterior chamber; posterior when the lens sinks into the vitreous. Can have same signs as lens subluxation.
  • Acute or chronically painful eye with episcleral injection and diffuse or central corneal edema.
  • Glaucoma more common in anterior lens luxation.
  • Uveitis.
  • Cataracts.
  • Retinal detachment.

 

CAUSES & RISK FACTORS

  • Primary—associated with ADAMTS17 gene mutation in some breeds; inheritance pattern uncertain in others.
  • Primary luxation and primary glaucoma—may occur simultaneously in some breeds.
  • Uveitis, especially chronic lens-induced uveitis.
  • Intraocular neoplasia—may physically luxate the lens or cause chronic inflammation, leading to zonular degeneration.
  • Trauma—rarely causes a normal lens to luxate without signs of severe uveitis or hyphema.
  • Cataracts—when intumescent or resorptive, can cause tension and breakage of lens zonules.

 

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Uveitis, glaucoma—also cause painful, red eyes with corneal edema and may be concurrent.

Buphthalmia may cause lens luxation.

Corneal endothelial dystrophy or degeneration—may also cause corneal edema.

Diagnosis made by careful ophthalmic examination and history.

 

CBC/BIOCHEMISTRY/URINALYSIS

Normal, unless sequela of a systemic disease that causes uveitis or neoplasia.

 

IMAGING

Thoracic radiographs and abdominal ultrasonography—may be indicated if secondary to intraocular neoplasia.

Ocular ultrasonography—useful if corneal edema or cloudy ocular media preclude examination.

 

DIAGNOSTIC PROCEDURES

Complete ophthalmic examination, including tonometry.

Genetic DNA test is available for some breeds predisposed to lens luxation.

 

TREATMENT

Potentially visual eyes—consider referral for surgical removal of the lens.

Manual transcorneal reduction of anterior lens luxation followed by medical management of a posterior luxation has been described.

Often, topical miotic therapy can keep a posteriorly luxated lens behind the pupil and surgery can be avoided in some cases.

Irreversibly blind eyes can be treated by enucleation or evisceration with intrascleral prosthesis; if secondary to neoplasia, enucleation is the best choice for therapeutic and diagnostic purposes.

 

MEDICATIONS

FOLLOW-UP

Medically treated primary posterior luxation—IOP rechecked 24 hours after starting treatment and frequently thereafter; once IOP is stable, re-examine patient 3 or 4 times/year.

Monitor for secondary glaucoma and retinal detachment.

If only one lens is involved at the time of examination, the other lens may eventually become involved; the ophthalmologist may choose to perform prophylactic phacoemulsification in the contralateral eye if not yet luxated.

 

MISCELLANEOUS

ABBREVIATION

IOP = intraocular pressure

 

Visit your veterinarian as early recognition, diagnosis, and treatment are essential.

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