LENS LUXATION

The lens is the transparent structure within the eye which assists focusing. It is a flattened sphere which is held in place by tiny ligaments around its circumference.

Two main disease problems beset the dog's lens, these are cataract and lens luxation.

Lens luxation

In some dogs, particularly the terrier breeds, the ligaments can break down allowing the lens to dislocate from its normal condition. It can fall backwards into the eye - posterior luxation - where it rarely causes discomfort or can fall forwards - anterior luxation - where it blocks the drainage of fluid from the eye allowing a build up of pressure, or glaucoma to develop. This is extremely painful and can cause permanent blindness.

Specialist surgical removal of an anteriorly displaced lens is the only possible treatment.

The surgery

Once the eye has been prepared for surgery it is opened with a tiny incision near or through the clear cornea and the dislocated lens is removed. The eye is closed with sutures which are absorbable and thus do not need to be removed. Sometimes further stitches are also placed in the corner of the eye (the canthus) but these again are usually dissolvable.

Post operative care

Your dog may have to stay at the practice for a few days after surgery for careful monitoring, treatment and rest. Once home it is vital that he/she is kept as quiet as possible and not allowed to jump up or to run up and down stairs. Lead exercise only is allowed for a few weeks. Remember the eye has been opened and it does take time to heal properly.

Eye medication will be dispensed and it is important that instructions are carefully followed.

Vision

The aim of the surgery is to alleviate discomfort and save vision as much as possible. If the lens has been dislocated for any length of time the chance of restoring vision is reduced although hopefully some guidance vision can be saved. In earlier cases quite good vision can be maintained although it will never be as good as prior to the lens dislocating since the eye can no longer focus on objects.

Complications

Complications can occur in some cases. These include persistent glaucoma, (increased pressure within the eye) despite the fact the lens has been removed. This complication can be difficult to treat successfully.

Another potential complication is retinal detachment where the retina or light sensitive surface is pulled off the back of the eye as the lens has moved forwards. These eyes often remain sightless but they are usually pain free.

Hereditary lens luxation

Weakness of the lens ligaments is known to be hereditary in the terrier breeds and also the Border Collie. Therefore in these breeds if one lens has luxated it is almost certain that the same thing will happen to the other eye at a later date. It is therefore important that you watch for any signs of discomfort or change of appearance of the eye and call your veterinarian immediately if you are at all concerned.

Partial lens luxation

Before the lens falls out of position completely it can wobble as some of the ligaments break but a few still remain to keep it loosely in place. This is what is known as sub-luxation of the lens. Some veterinary ophthalmologists like to operate on these before they dislocate completely so the eye does not exhibit pain and glaucoma that can follow total anterior luxation.

However others prefer to leave them until they do luxate because the potential complications are still present if the lens is operated on when sub-luxated. These have been described above.

Posterior lens luxation

When the lens falls into the back of the eye it causes little or no discomfort. These cases can sometime be left. The surgery is technically very demanding and the risk of complication greater. The danger is that the lens still move around in the eye and can sometimes fall forwards, converting into an anterior luxation. This can be followed by discomfort and blindness as already described.

If your dog has a posterior luxation you will be asked to monitor it carefully and seek specialist veterinary attention if there are any signs of discomfort or a change of appearance in the eye.

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