Ectopia lentis is a displacement or malposition of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

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

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...

s. 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 A cataract is a cloudy area in the lens (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...

formation (decrease in lens diameter may stretch and break the zonules), or

glaucoma Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...

(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 Uveitis () is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. The uvea consists of the middle layer of pigmented vascular structures of the eye and ...

(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 The anterior chamber ( AC) is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Hyphema, anterior uveitis and glaucoma are three main pathologies in this area. In hyphema, ...

of the eye. This can cause glaucoma, uveitis, or damage to the

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, 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 blood 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 po ...

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 The vitreous body (''vitreous'' meaning "glass-like"; , ) is the clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) in humans and other vertebrates. It is often referred to as the vitreous hum ...

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

conjunctiva In the anatomy of the eye, the conjunctiva (: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with gobl ...

l 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, Jack Russell Terrier, Wirehaired Fox Terrier,

Rat Terrier The Rat Terrier is an American dog breed with a background as a farm dog and hunting companion. They share much ancestry with the small hunting dogs known as feists. Common throughout family farms in the 1920s and 1930s, they are now recognize ...

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 The Shar Pei () is a dog breed from southern China. Traditionally kept as a property guardian, the shar pei was driven to the brink of extinction in the 20th century. The breed is known in the West for its deep wrinkles, while a traditional less ...

, and

Border Collie The Border Collie is a British list of dog breeds, breed of herding dog of the collie type of medium size. It originates in the region of the Anglo-Scottish border, and descends from the traditional Sheep dog, sheepdogs once found all over the ...

. 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 Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...

Labrador Retriever The Labrador Retriever or simply Labrador or Lab is a British list of dog breeds, breed of water dog retriever gun dog. It was developed in the United Kingdom from St. John's water dogs imported from the Newfoundland Colony, colony of Newfoun ...

s and

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

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 dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically ha ...

(upward and outward) *

Homocystinuria Homocystinuria (HCU) is an inherited disorder of the metabolism of the amino acid methionine due to a deficiency of cystathionine beta synthase or methionine synthase. It is an inherited autosomal recessive trait, which means a child needs to ...

(downward and inwards) * Weill–Marchesani syndrome * Sulfite oxidase deficiency *

Molybdenum cofactor deficiency Molybdenum cofactor deficiency is a rare human disease in which the absence of molybdopterin – and consequently its molybdenum complex, commonly called molybdenum cofactor – leads to accumulation of toxic levels of sulphite and neurological d ...

Hyperlysinemia Hyperlysinemia is an autosomal recessive metabolic disorder characterized by an abnormal increase of lysine in the blood, but appears to be benign. It is caused by mutations in '' AASS'', which encodes α-aminoadipic semialdehyde synthase. Hype ...

Less common: *

Ehlers–Danlos syndrome Ehlers–Danlos syndromes (EDS) is a group of 14 genetic connective-tissue disorders. Symptoms often include loose joints, joint pain, stretchy velvety skin, and abnormal scar formation. These may be noticed at birth or in early childhood. Co ...

* Crouzon disease * Refsum syndrome * Kniest syndrome * Mandibulofacial dysostosis *

Sturge–Weber syndrome Sturge–Weber syndrome, sometimes referred to as encephalotrigeminal angiomatosis, is a rare congenital neurocutaneous disorder (also known as phakomatoses). It is often associated with port-wine stains of the face, glaucoma, seizures, intellect ...

* Conradi syndrome * Pfaundler syndrome *

Pierre Robin syndrome Pierre Robin sequence (; abbreviated PRS) is a congenital defect observed in humans which is characterized by facial abnormalities. The three main features are micrognathia (abnormally small mandible), which causes glossoptosis (downwardly displ ...

* Wildervanck syndrome * Sprengel deformity

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