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
The lens may luxate backwards
into the posterior chamber or forward into the anterior chamber.
Early clinical signs,
include inflammation within the eye (uveitis), and pain with the surrounding
white area of they eye (sclera) becoming inflamed and red in appearance.
The pressure within the eye can increase producing swelling of the eye
(glaucoma) especially with anterior luxations. If the lens falls forward
onto the cornea (the clear surface of the eye) then it can cause swelling (edema)
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 coloured part (iris) 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.
Treatment of lens luxation
will nearly always require surgery to remove the lens. If the problem has
been identified early enough vision may be saved, although somewhat
diminished after the lens is removed. 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.
Dogs affected with primary lens luxation should
not be used for breeding. Since this is a late
onset disease, the breeder may encounter a situation where a dog who has
already produced a number of litters develops a lens luxation. This is
disconcerting since it would be advisable not to use any of the second
generation for breeding either.
eye certification examinations will not, in
most cases, detect a dog pre-disposed to lens luxation, unless the ligaments
have already started to weaken and a slight wobble of the lens is detected
by the ophthalmologist during the examination.