Dislocation of the eye lens is considered an emergency that requires immediate diagnosis and aggressive treatment. The condition can cause permanent blindness within a few hours of onset.

The eye lens is the clear part of the eye that focuses light and images on the retina. It is held in place by fibrous strands called zonules. If these strands break or degenerate, the lens can separate and move out of place. This dislocation of the eye lens is also called lens luxation. Although rarely seen in cats, the condition causes increased pressure in the eye and is extremely painful for affected animals.

Symptoms of a dislocated lens may include one or more of the following:

Lens luxation can be categorized based on the extent of dislocation and the placement of the dislocated lens. Subluxation refers a partial dislocation in which the lens remains in its proper place, while luxation is a complete dislocation of the lens. 

The lens may move forward into the front of the pupil, known as anterior displacement, or backward into the vitreous. Anterior displacement is more common in inherited cases and is often seen in young to middle-aged animals. Older animals typically experience posterior displacement.

Primary lens luxation is caused by an inherited disorder. The condition typically presents itself from a young age up until four to seven years.

Secondary luxation occurs concurrently with other eye disorders that cause zonule breakage. Causes include:

If a cat is showing signs of eye pain like rubbing the face and eye area, owners should examine it for the presence of other common symptoms. A noticeable decrease in vision on one side with no other symptoms may indicate that a posterior luxation has occurred. If an eye lens dislocation is suspected, it’s important to seek emergency veterinary care immediately. 

The vet will provide a thorough physical examination to look for abnormalities in the eye and measure eye pressure. The exam is typically performed using local anesthetic eye drops. A thoracic x-ray or ultrasound may also be recommended. Blood tests and other laboratory tests may be ordered to rule out other conditions that may be causing the symptoms.

The recommended course of treatment depends on whether the dislocation is full or partial, the location of the displaced lens, and the cat’s current visual abilities. 

Immediate focus should be on lowering pressure in the eye as this can cause damage to the retina and optic nerve. Oral and topical medications including antibiotics and corticosteroids will often be prescribed. It is likely that your vet will want to consult with a veterinary ophthalmologic specialist. Lens removal may be recommended and should occur as soon as possible.

Surgery is almost always needed to treat anterior lens luxation. A small incision will be made in the eye in order to remove the dislocated lens. If the cat has already gone blind in the affected eye, removal of the eyeball (enucleation) may be recommended to treat pressure and eliminate pain. A prosthesis may be used to replace the eye. Possible post-surgical complications include blindness, ongoing glaucoma, eye bleeding, or detachment of the retina. 

When the lens has moved to the back of the eye, it is difficult to surgically remove. As long as the lens can stay in position, the veterinarian may decide to leave it alone as this type of displacement is less likely to cause vision problems. Long-term use of eye drops may be needed to keep the pupil small and ensure that the lens stays in position.

In the case of primary luxation, it is likely that both eyes will eventually be affected. After a cat presents with luxation in one eye, the other should be carefully monitored. Proactive removal of the unstable lens can help to preserve vision, and owners should seek treatment at the first sign of instability.

Cats should be re-examined within 24 hours after treatment and follow-up visits will be recommended every three months thereafter. 

If surgery is performed, the cat will likely be kept in the hospital for one or two days for monitoring and then will be released with a prescription for pain medication and antibiotics. The likelihood that the surgery will be successful depends on the degree of dislocation and the amount of time that passed by prior to surgery. 

Most pets are able to cope with living without a lens, but it will take time for them to adapt to the resulting vision changes. If the eye is not removed, it is likely that long-term use of medication will be necessary to control eye pressure.