Ectopia lentis is a displacement or malposition of the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

's crystalline lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or luxated lens.

Ectopia lentis in dogs and cats

Although observed in humans and cats, ectopia lentis is most commonly seen in dogs. Ciliary zonules normally hold the lens in place. Abnormal development of these zonules can lead to primary ectopia lentis, usually a bilateral condition. Luxation can also be a secondary condition, caused by trauma, cataract formation (decrease in lens diameter may stretch and break the zonules), or glaucoma (enlargement of the globe stretches the zonules). Steroid administration weakens the zonules and can lead to luxation, as well. Lens luxation in cats can occur secondary to anterior uveitis (inflammation of the inside of the eye).

Anterior lens luxation

With anterior lens luxation, the lens pushes into the iris or actually enters the anterior chamber of the eye. This can cause glaucoma, uveitis, or damage to the cornea. Uveitis (inflammation of the eye) causes the pupil to constrict (

miosis Miosis, or myosis (), is excessive constriction of the pupil.Farlex medical dictionary
citing: ...

) and trap the lens in the anterior chamber, leading to an obstruction of outflow of

aqueous humour The aqueous humour is a transparent water-like fluid similar to plasma, but containing low protein concentrations. It is secreted from the ciliary body, a structure supporting the lens of the eyeball. It fills both the anterior and the posterio ...

and subsequent increase in ocular pressure (glaucoma). Better prognosis is valued in lens replacement surgery (retained vision and normal intraocular pressure) when it is performed before the onset of secondary glaucoma. Glaucoma secondary to anterior lens luxation is less common in cats than dogs due to their naturally deeper anterior chamber and the liquification of the vitreous humour secondary to chronic inflammation. Anterior lens luxation is considered to be an ophthalmological emergency.

Posterior lens luxation

With posterior lens luxation, the lens falls back into the vitreous humour and lies on the floor of the eye. This type causes fewer problems than anterior lens luxation, although glaucoma or ocular inflammation may occur. Surgery is used to treat dogs with significant symptoms. Removal of the lens before it moves to the anterior chamber may prevent secondary glaucoma.

Lens subluxation

Lens subluxation is also seen in dogs and is characterized by a partial displacement of the lens. It can be recognized by trembling of the iris ( iridodonesis) or lens ( phacodonesis) and the presence of an aphakic crescent (an area of the pupil where the lens is absent). Other signs of lens subluxation include mild conjunctival redness, vitreous humour degeneration, prolapse of the vitreous into the anterior chamber, and an increase or decrease of anterior chamber depth. Removal of the lens before it completely luxates into the anterior chamber may prevent secondary glaucoma. Extreme degree of luxation of lens is called "lenticele" in which lens comes out of the eyeball and becomes trapped under the Tenon's capsule or conjunctiva. A nonsurgical alternative treatment involves the use of a miotic to constrict the pupil and prevent the lens from luxating into the anterior chamber.

Breed predisposition

Terrier breeds are predisposed to lens luxation, and it is probably inherited in the

Sealyham Terrier The Sealyham Terrier ( cy, Daeargi Sealyham) is a rare Welsh breed of small to medium-sized terrier that originated in Wales as a working dog. It is principally a white-bodied, rough-coated breed, developed in the mid-to-late-19th century by ...

, Jack Russell Terrier, Wirehaired Fox Terrier, Rat Terrier,

Teddy Roosevelt Terrier The Teddy Roosevelt Terrier is a small to medium-sized American hunting terrier. It is lower-set, with shorter legs, and is more muscular with heavier bone density than the related American Rat Terrier. Much diversity exists in the history of ...

, Tibetan Terrier, Miniature Bull Terrier, Shar Pei, and Border Collie. The mode of inheritance in the Tibetan Terrier and Shar Pei is likely

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

. Labrador Retrievers and

Australian Cattle Dog The Australian Cattle Dog (ACD), or simply Cattle Dog, is a breed of herding dog originally developed in Australia for droving cattle over long distances across rough terrain. This breed is a medium-sized, short-coated dog that occurs in two m ...

s are also predisposed.

Systemic associations in humans

In humans, a number of systemic conditions are associated with ectopia lentis:Eifrig CW, Eifrig DE
"Ectopia Lentis"
eMedicine.com. November 24, 2004. More common: *

Marfan syndrome Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints a ...

(upward and outward) * Homocystinuria (downward and inwards) * Weill–Marchesani syndrome *

Sulfite oxidase deficiency Sulfite oxidase () is an enzyme in the mitochondria of all eukaryotes, with exception of the yeasts. It oxidizes sulfite to sulfate and, via cytochrome c, transfers the electrons produced to the electron transport chain, allowing generation of A ...

* Molybdenum cofactor deficiency * Hyperlysinemia Less common: * Ehlers–Danlos syndrome * Crouzon disease *

Refsum syndrome Refsum disease is an autosomal recessive neurological disease that results in the over-accumulation of phytanic acid in cells and tissues. It is one of several disorders named after Norwegian neurologist Sigvald Bernhard Refsum (1907–1991). Ref ...

* Kniest syndrome * Mandibulofacial dysostosis * Sturge–Weber syndrome *

Conradi syndrome Conradi is a surname. It comes from the Germanic Konrad: ''kuoni'' and ''rad'' meaning happy or laughing or ''rat'' meaning daring/experienced counsel. * August Conradi (1821–1873), German composer * Edward Conradi (1869–1944), American educa ...

* Pfaundler syndrome * Pierre Robin syndrome *

Wildervanck syndrome Wildervanck syndrome or cervico-oculo-acoustic syndrome comprises a triad of: * Duane syndrome Duane syndrome is a congenital rare type of strabismus most commonly characterized by the inability of the eye to move outward. The syndrome was firs ...

Sprengel deformity Sprengel's deformity (also known as high scapula or congenital high scapula) is a rare congenital skeletal abnormality where a person has one shoulder blade that sits higher on the back than the other. The deformity is due to a failure in early f ...

References

External links

GeneReviews/NCBI/NIH/UW entry on ADAMTSL4-Related Eye Disorders, Autosomal Recessive Isolated Ectopia Lentis, Ectopia Lentis et Pupillae
{{Congenital malformations and deformations of eye, ear, face and neck Dog diseases Cat diseases Congenital disorders of eyes Disorders of lens