Lens luxation

The lens, which is situated in the middle of the eye behind the pupil, changes its shape to allow the eye to focus. This is achieved by tightening of fine ligaments called zonules attached around the perimeter of the lens which suspend it within the eye When these zonules are damaged or broken the lens can luxate (shift out of place). The lens may luxate backwards into the posterior chamber of forward into the anterior chamber.

Early clinical signs include uveitis (inflammation within the eye), and pain with the surrounding sclera (white area of the eye) becoming inflamed and red in appearance. The pressure within the eye can increase producing glaucoma (swelling of the eye) especially with anterior luxations. If the lens falls forward onto cornea (the clear surface of the eye) then it can cause edema (swelling) and a blue-cloudy appearance at the site of contact. The lens is often visible in front of the eye with anterior luxations whereas with posterior luxations the anterior chamber appears deepened and the iris (colored part) may move abnormally.

Causes of lens luxation include trauma; disease within the eye including tumors, glaucoma and occasionally cataracts; or a genetically inherited weakness in the zonules. Border Collies, any Terrier breeds, Poodles and the Australian Cattle Dog are all known to have an increased risk of developing lens luxation. Dogs are more likely to inherit the problem whereas cats are more prone to lens luxation secondary to trauma or disease within the eye.

Treatment of lens luxation will nearly always require surgery to remove the lens. If the problem has been identified early enough then vision may be saved although somewhat diminished after the lens is extracted. If vision is already lost then options such as eye removal or eye prosthesis may be considered. If one eye is affected then there is a higher risk in the future of the other eye developing a luxation.