Feline Lens Luxation
Lens luxation is the dislocation or displacement of the lens within the eye. The lens is the clear structure in the eye, consisting of two rounded or convex surfaces, that focuses light rays to form an image onto the retina. Normally the lens is suspended between the iris (the colored portion of the eye) and the vitreous (the clear gel in the back of the eye), and is held in place by small fibers called zonules or suspensory ligaments.
Should the zonules break, the lens can either become partially dislocated (subluxated) from its normal position or completely dislocated (luxated). When the lens detaches and falls forward into the anterior chamber in front of the pupil, it is called an anterior luxation. When it falls back into the rear portion of the eye, it is called a posterior luxation.
Causes of Lens Luxation in Cats
Cats are prone to lens luxation secondary to inflammation within the eye.
Secondary luxation may also be associated with the following:
What to Look For
You may not notice signs of subluxation of the lens, but subluxations can be detected by a veterinarian during an eye examination. Most symptoms occur with anterior luxations. With posterior luxations, signs are often not apparent. Signs may include the following:
Diagnosis of Lens Luxation in Cats
Diagnosis is made by discovery of the lens in the anterior chamber, on the floor of the vitreous cavity, or no longer centered in the normal position. Your veterinarian may perform the following diagnostic tests:
Your veterinarian may refer your cat to a veterinary ophthalmologist for further evaluation and performance of the above tests using specialized instrumentation.
Treatment of Lens Luxation in Cats
The treatment of lens luxation varies depending on the location of the lens, the presence of acute glaucoma, and the potential for vision. The main goals of treatment include lowering the pressure in the eye (IOP), surgical removal of anteriorly luxated lenses (in eyes with a potential for vision), and treatment of any underlying causes.
Because lens luxations and subluxations in the cat are usually secondary to anterior uveitis, treatment for the uveitis may take precedence over treatment of the lens dislocation.
The first priority is to assess the eye for vision and the presence of glaucoma. If an anterior luxation and elevated IOP have been present for more than 48 hours, the eye may be permanently blind. If the luxation is recent or acute, if the glaucoma is not severe, and the retina and optic disc still look healthy, then there may be a reasonable chance of saving vision.
Treatment may include the following:
Home Care and Prevention
Following initial therapy, the pressure within the eye (IOP) is monitored closely, and all medications are continued at home.
Uveitis is often a chronic disease in cats and requires long-term therapy. Glaucoma due to the uveitis or the lens dislocation can be frustrating to treat. Repeated recheck examinations are often needed to monitor response to therapy, and to watch for flare-ups.
Your veterinarian may instruct you to watch for signs of glaucoma such as redness, eye swelling, pain and squinting.
Most cases of lens luxation cannot be prevented. Keeping cats indoors and not allowing them to roam free or to fight with other cats decreases their risk of exposure to the feline viral diseases that cause uveitis and that lead to lens luxation.