The lens normally sits behind the iris (colour of the eye). A lens luxation is when the lens moves from its normal position. This can be following an eye injury, or there may be no history of an injury.
Many breeds of dogs, especially Terriers, are predisposed to lens luxation. Breeds most commonly seen in Australia include Fox Terriers, Jack Russell Terriers, Australian Cattle Dogs and German Shepherds. In pure breed dogs it is common for both eyes to be affected.
Anterior Lens Luxation
This is where the lens comes forward into the anterior chamber of the eye. Painful sequelae such as glaucoma (increased pressure inside the eye), or uveitis (inflammation/reaction) can quickly develop.
If the eye is still healthy surgery is advised to remove the lens. Without surgery over 95% of eyes will go blind, often with pain.
Posterior Lens Luxation
This is where the lens moves backwards into the eye. If the pressure is stable, surgery isn't required immediately. Patients can be treated with medications to make the pupil miotic, which doesn't allow the lens to move around in the eye. Sometimes when the lens is shifting back and forth freely, and the pressures are stable surgery is suggested because the retina is at a higher risk of being damaged.
The surgery for lens removal is quite involved and your pet will require a specialised general anaesthetic. The surgical technique is to remove the lens in one piece via a large incision at the top of the eye. In some cases part of the vitreous (jelly at the back of the eye) is also removed. The incision is then closed with fine hair-like dissolving sutures.
The success rate - vision 12 months after surgery - is over 90% for lenses that are removed whilst loose or posteriorly luxated without clinical symptoms. For lenses that are luxated anteriorly or have glaucoma the success rate can drop to as low as 50% depending on how long the lens has been anterior and how high the intraocular pressure is. Failure to regain vision is due to irreversible damage to the nerve tissue due to increased pressure.
Unfortunately there are possible complications that may occur after surgery1. Glaucoma (increased intraocular pressure) - anti-glaucoma medication may be required
2. Corneal oedema (blue eye)
3. Retinal detachment
5. Pupil of the eye may appear distorted due to the removal of the lens and vitreous. This does not seem to affect vision, but may in some cases make the patient more sensitive to sunlight.
6. However, without surgery most eyes with lens luxation go blind.
As the vitreous (Jelly of the eye) is often abnormal due to the lens luxation the risk of retinal detachment is greatly increased and with intraocular surgery. This is where the retina becomes detached from the back of the eye. In all cases of lens luxation we recommended a procedure called Retinopexy with laser surgery. This is where we weld the retina onto the back of the eye to reduce the risk of detachment. We do this procedure in both eyes, as it is possible for a lens luxation to develop in the other eye especially in purebred dogs.
Unfortunately even with this procedure it is still possible for the retina to detach, but much less frequently.
Vision after Surgery
After surgery, vision can be poor in the operated eye for several days to a few weeks. Vision will return as the eye clears after surgery as long as the nerve tissue is healthy. This may mean that a one-eyed dog may be blind for a few days. Generally the patient's close up vision (less than 75cms) is poor after the lens is removed, however the mid to long distance vision is normal. In some cases it may take up to 6 weeks for the dog to learn how to see again. Most owners report that their dog has good vision after surgery.
Lens luxations in cats are usually caused from the patient suffering from chronic uveitis - long-term inflammation.
Cats appear to deal better with lens luxations compared to dogs. Their IOP can be fairly comfortable therefore they can be treated with glaucoma drops and tablets to keep them comfortable. Surgery is usually required when the eye is very uncomfortable with a high IOP. Cats don't seem to have many post op problems.