ADVICE

Lens luxation

The lens is located in the central region of the eye, where its purpose is to transmit and focus light onto the retina at the back of the eye.

The lens is anchored in place by numerous fibres, called lens zonules. If these fibres break down, the lens begins to drift from its central position. Lens luxation occurs when all of these fibres are broken and the lens becomes loose within the eye, where it can move forwards or (less commonly) backwards.

Lens luxation is an inherited condition in dogs that typically affects the terrier breeds (most commonly the Jack Russell terrier) and the Lancashire heeler. In cats, it is usually a consequence of inflammation within the eye (uveitis).

What are the signs of lens luxation?

Initial signs are a sudden onset of eye pain, clouding, and redness of the 'white' of the eye. The dog may hold its eye shut and there may be a watery discharge. Lens luxation is an emergency and the dog should be referred to an ophthalmologist without delay. When the lens luxates, the pressure inside the eye rapidly rises to cause glaucoma and blindness, which is irreversible without urgent treatment.

What are the treatment options for lens luxation?

Initial treatment consists of pain relief and anti-glaucoma treatment to reduce the ongoing damage to the retina and optic nerve. Following this, there are two options, non-surgical and surgical:

Non-surgical intervention under topical anaesthetic or light sedation – 'couching' of the lens

This involves applying careful pressure through the cornea in order to reduce the lens back behind the iris, and then trapping it there by inducing miosis with a prostaglandin analogue (latanoprost). 'Couching' has been recently studied and found to have comparable success rates to surgical intervention. However, sometimes it is not successful due to long-standing chronic inflammation which cause adherences between the lens and the pupil and hyper-hydration of the vitreous body.

Surgical intervention under general anaesthesia – extracapsular lens extraction and intracapsular lens extraction

Lens luxation is an inherited disorder, and the lens of the other eye is also likely to become affected. For this reason, we may prescribe preventative treatment with eye drops that constrict the pupil to help prevent the lens falling forwards (if we do this, it is vital that the drops are given twice daily every day, and that you stop the drops and contact us if the eye becomes suddenly painful).

In advanced cases of lens luxation, when the eye is irreversibly painful and blind, removal of the eye may be advised.

What happens after the procedure?

Following couching or removal of the luxated lens, your pet should regain useful vision.

However, because the eye no longer has a lens inside it, vision will not be as good as previously. Without a lens, the eye is severely long-sighted. Objects will appear out of focus and slightly larger than normal, and it will take some weeks for your pet to get used to this. Their distant vision is usually better than their close vision, and they may have some problems in locating objects close by. However, they usually learn to cope reasonably well.

Even following successful couching or surgery, it is important to remember that serious potential postoperative complications are still possible, including retinal detachment and glaucoma.

To reduce the risk of such complications, we recommend regular (three to six monthly) rechecks and long-term medication.