What Is The Lens?
The lens is a transparent tissue which helps the eye to focus light and images on the back part of the eye.
This is the part of the eye which can develop a cataract. In normal health, the lens is held in place behind the iris and pupil by multiple zonular fibers. In the office, we will compare the lens and its fibers to a trampoline and its springs. These fibers can become damaged for a few reasons, and instability of the lens can lead to a subluxation or complete luxation (dislocation) of the lens. A lens luxation can be a surgical emergency based on the cause of the luxation, secondary complications, and overall health of the eye involved.
What Is A Lens Luxation?
The early stages of a lens instability, or lens subluxation, usually are not noticeable outside of a specialized veterinary eye exam. A lens subluxation occurs when a few lens fibers are broken, but the lens still remains
behind the pupil. At this stage, dogs and cats usually will not show signs of discomfort or changes in vision. When all lens fibers have become damaged, the lens will become fully luxated. A posterior lens luxation involves the lens falling to the back portion of the eye. This can lead to discomfort, squinting and redness around the eye. Inflammation inside of the eye (uveitis) is also common following a posterior lens luxation.
What Is An Anterior Lens Luxation?
If the lens is dislocated through the pupil to the front of the eye, it has become anteriorly luxated. Dogs and cats with an anterior lens luxation will squint the affected eye due to discomfort. The luxated lens can cause damage to the back of the cornea leading to corneal edema and scarring. Patients can develop inflammation inside of the eye and redness around the eye. Due to inflammation inside of the eye, abnormal positioning of the lens, and changes to fluid flow inside of the eye, dogs and cats with an anterior lens luxation are at high risk for developing secondary glaucoma. Glaucoma can be a painful and blinding
condition for the eye.
What Causes A Lens Luxation?
There are a few causes for anterior lens luxation in small animals. The Border Collie and Terrier breeds can have an inherited predisposition, although other breeds are known to be predisposed and any dog or cat can develop a lens luxation due to abnormal lens fiber development or degeneration. Chronic intraocular inflammation, advanced cataracts and stretching of the eye (buphthalmos) due to chronic glaucoma can lead to a secondary lens luxation. In most cats, a lens luxation occurs secondary to glaucoma or uveitis.
How Is A Lens Luxation Treated?
Depending on the cause of the lens luxation and the secondary complications present, medical or surgical therapy may be recommended. If a lens luxation is identified quickly and it is believed that the dog or cat
could maintain vision following lens removal, surgery is oftentimes recommended emergently. Pre-anesthetic blood work to make sure a pet is safe for surgery and retinal function testing may be performed prior to surgery. If a pet cannot receive general anesthesia, if their lens is luxated to the back of the eye or if they are otherwise non-visual and comfortable, medical management may be used in select cases. If the condition is recognized early, before a complete luxation has occurred, medications to constrict the pupil can help to control eye pressure and keep the lens behind the iris and lens.
What Happens If A Lens Luxation Is Not Treated or Referred Too Late?
If left untreated, dogs can develop painful glaucoma or irritating inflammation associated with the dislocated lens. If an animal has been blind prior to a diagnosis of a lens luxation, additional surgical procedures may be used to improve overall comfort. In order to maintain vision in the eye, emergency surgery may be indicated
to remove a luxated lens. Based on your dog or cat’s eye exam, surgery can be quite successful at improving comfort and vision. Your ophthalmologist is your best advantage to determine the right course of action to keep your pet comfortable and protect vision.