Lens luxation

What is ... ?: 

 With this disorder there is abnormal positioning of the lens within the eye. Normally the lens is suspended between the iris and the retina, held in position by the lens zonules and the adjacent vitreous (see diagram). There can be partial (sub-luxation) or complete displacement (luxation) of the lens from its normal site, either forward into the anterior chamber of the eye (in front of the pupil) or backward into the vitreous.

Forward (anterior) lens luxation in particular may cause an increase in the pressure within the eye (glaucoma), which if untreated leads to blindness.
Lens luxation may be primary (inherited), with certain breeds predisposed as listed below. Secondary luxation may occur in any breed as a result of trauma, inflammation, glaucoma or an intraocular tumour.  

How is ... inherited?: 

The mode of inheritance is not defined.

What does ... mean to your dog & you?: 

 Inherited (primary) lens luxation occurs in young to middle-aged animals of 4 to 7 years. The lens usually displaces forward into the anterior chamber.  In older animals, the lens displaces more easily backwards into the vitreous space.

A lens that displaces forward into the anterior chamber will often cause increased pressure within the eye leading to glaucoma. This is an emergency, as increased intraocular pressure can cause blindness within several hours. Your dog will experience intense pain and tearing of the eye, as well as reduced vision. With these signs, your dog should see your veterinarian immediately to prevent irreversible loss of vision.
Other signs of lens luxation are that your dog's eyes may appear asymmetrical to you or the affected eye may look cloudy. Sub-luxations and posterior luxations may ultimately result in glaucoma as well.
In predisposed breeds, lens luxation often occurs in both eyes at the same time, or in the second eye within a few months of the first.

How is ... diagnosed?: 

 With an anterior luxation, your dog may show intense pain (rubbing, pawing at the eye), tearing and visual impairment associated with glaucoma. Alternately, your dog may show no clinical signs associated with the lens luxation (usually a sub- or posterior luxation) and your veterinarian may observe an ocular abnormality during a routine physical examination. He/she will examine your dog's eye with an ophthalmoscope and measure the intraocular pressure. This can usually be done with local anaesthetic drops placed in your dog's eye.

How is ... treated?: 

 Treatment depends on the location of the lens (anterior or posterior), the presence or absence of acute glaucoma, and the potential for vision.

With sudden anterior lens luxation, your veterinarian will immediately start medical therapy for glaucoma. The lens should be surgically removed as soon as possible.  If the intraocular pressure is elevated, then surgery is urgent to prevent permanent damage to the retina and optic nerve. Pressures over 50 mm Hg will cause such damage within hours.
For dogs with anterior lens luxation that have become blind, glaucoma can be treated by removing the globe of the eye (enucleation). This will eliminate the pain for your dog. There are also procedures that can be done that preserve the globe such as placing a prosthesis.
Posterior luxated lenses are difficult to remove surgically. As long as the lens can be maintained in that position, problems with vision are less likely. Long-term eyedrops can be used to keep the pupil small and the lens behind it.

For the veterinarian: 

 

  1.      PHYSICAL EXAM: may see blepharospasm, epiphora, central corneal edema
  2.      OPHTHALMOSCOPIC EXAM: may see increased or decreased anterior chamber depth, iridodonesis, aphakic crescent, central corneal edema; with anterior displacement the IOP is generally elevated ( IOP of 50 mm Hg or more will lead to permanent optic nerve and retinal damage within hours if not relieved); IOP may be decreased due to uveitis caused by lens irritation.
Breeding advice: 

 Dogs that have experienced lens luxation should not be used for breeding. However this condition often does not occur before 4 to 7 years of age, making it difficult to identify affected dogs before they are used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources: 

 Morgan, R.V. 1994. Ocular emergencies - part 2.   A.C.V.I.M. - Proceedings of the 12th Annual Veterinary Medical Forum. p. 52-56.


What breeds are affected by ... ?
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