List of systemic diseases with ocular manifestations.Homocystinuria (downward and inwards).In humans, a number of systemic conditions are associated with ectopia lentis: Labrador Retrievers and Australian Cattle Dogs are also predisposed. The mode of inheritance in the Tibetan Terrier and Shar Pei is likely autosomal recessive. Terrier breeds are predisposed to lens luxation, and it is probably inherited in the Sealyham Terrier, Jack Russell Terrier, Wirehaired Fox Terrier, Rat Terrier, Teddy Roosevelt Terrier, Tibetan Terrier, Miniature Bull Terrier, Shar Pei, and Border Collie. A nonsurgical alternative treatment involves the use of a miotic to constrict the pupil and prevent the lens from luxating into the anterior chamber. 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. Removal of the lens before it completely luxates into the anterior chamber may prevent secondary glaucoma. 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. 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). Lens subluxation is also seen in dogs and is characterized by a partial displacement of the lens. Removal of the lens before it moves to the anterior chamber may prevent secondary glaucoma. Surgery is used to treat dogs with significant symptoms. This type causes fewer problems than anterior lens luxation, although glaucoma or ocular inflammation may occur. With posterior lens luxation, the lens falls back into the vitreous humour and lies on the floor of the eye. Anterior lens luxation is considered to be an ophthalmological emergency. 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. Better prognosis is valued in lens replacement surgery (retained vision and normal intraocular pressure) when it is performed before the onset of secondary glaucoma. Uveitis (inflammation of the eye) causes the pupil to constrict ( miosis) and trap the lens in the anterior chamber, leading to an obstruction of outflow of aqueous humour and subsequent increase in ocular pressure (glaucoma). This can cause glaucoma, uveitis, or damage to the cornea. With anterior lens luxation, the lens pushes into the iris or actually enters the anterior chamber of the eye. Lens luxation in cats can occur secondary to anterior uveitis (inflammation of the inside of the eye). Steroid administration weakens the zonules and can lead to luxation, as well. 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). ![]() Abnormal development of these zonules can lead to primary ectopia lentis, usually a bilateral condition. Ciliary zonules normally hold the lens in place. ![]() Although observed in humans and cats, ectopia lentis is most commonly seen in dogs.
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