The lens in the eye allows light to travel through the eye and reach the retina (the light receptors of the eye). The lens’ is held in place by the zonule (a biological elastic band) just behind the iris. “Lens luxation” indicates that the lens has become loose (due breakdown of the zonule) in the eye and moved to the front (anterior) or back (posterior) of the eye. If the lens moves in the eye the pressure in the eye may become elevated (glaucoma). Glaucoma is a blinding disease in dogs; therefore surgical removal of the displaced lens is recommended.
Most dogs which develop lens luxation are young dogs, which have an inherited predisposition (defect in the zonule). In the few breeds, where the inheritance has been studied in detail, the mode/type of inheritance was proven to be autosomal recessive – this means that the defective gene must be passed on by both the sire (father) and the dam (mother) to produce an affected animal.
The most common breeds affected include:
• Jack Russel (Parson) Terrier
• Rat Terrier
• Tibetan Terrier
• Smooth Fox Terrier
• Wirehaired Fox Terrier
• Shar Pei
If you own a purebred dog of one of the above breeds showing any type of eye irritation/ symptoms of ocular disease, you should contact a veterinary ophthalmologist to have an ocular examination. Early intervention is necessary in order to prevent permanent blindness due to lens luxation. This disease is occasionally seen in young adult mixed breed dogs. Prior to permanent luxation of the lens the eye changes seen may include:
• Vitreous (gel) in the anterior chamber of the eye.
• Phacodonesis (wobbling of the lens).
• Iridodonesis (wobbling of the iris).
• Deep anterior chamber (the distance between the cornea and the lens).