Cataracts in Dogs
Lorie Huston, DVM
Cataracts are a common problem in dogs and occur in the lens of your dog’s eye. In the normal canine eye, the lens aids in focusing the eye and should normally be clear without any opacities. Essentially, a cataract occurs when an opaque area forms within the lens of the eye, making it impossible for light to penetrate the affected area.
Causes of Cataracts in Dogs
There are numerous causes of cataracts in dogs, including:
• aging changes (cataracts are common in older dogs)
• congenital defects (dogs may be born with cataracts)
• genetic predisposition (some dogs are genetically disposed to developing cataracts)
• dietary deficiencies
• electrical shocks
• diabetes mellitus
Consequences of Canine Cataracts
A cataract results in an area of the lens which your dog is unable to see through. If both eyes are affected and the cataracts cover both lenses completely, your dog may become completely blind.
In addition, a lens afflicted with a cataract may luxate and move from its normal position within your dog’s eye. By doing so, the lens may block the normal flow of fluid through the structures of the eye, causing glaucoma as a result of an increase in the intraocular fluid levels.
Alternatively, a lens with a cataract may also absorb fluid and swell abnormally, again resulting in glaucoma when the swelling blocks the outflow of fluid from the eye causing an increase in intraocular pressure.
Cataracts can also begin to dissolve when they become mature and this dissolution may result in inflammation within the eye, known as uveitis. Uveitis is painful for your dog and can also lead to the development of glaucoma.
Diagnosis of Cataracts in Dogs
Cataracts can be mistaken for a number of different eye diseases and an ophthalmic examination is necessary to determine whether cataracts are present.
Cataracts must be differentiated from nuclear sclerosis, a normal increase in the compactness of the fibers of the lens that occurs as a dog ages. Though the resulting changes in the sclerotic lens can physically resemble a cataract, the dog is able to see normally through the lens.
Blindness and/or changes in vision do not occur with nuclear sclerosis.
A thorough ophthalmic examination by an experienced veterinarian can determine whether changes in the eye are a result of cataracts, nuclear sclerosis or other canine eye problems.
Cataract Surgery in Dogs
When treatment for a canine cataract is necessary, surgery is usually the only treatment option. Surgery for a cataract in a dog involves either:
• physically cutting into the eye and removing the lens with the cataract
• breaking up and removing the diseased lens using a procedure known as phacoemulsification
In phacoemulsification, sound waves are used to physically break apart the diseased lens. During phacoemulsification, the dog is under an anesthetic and medicated to induce paralysis to prevent the dog from blinking or otherwise moving the eye. Once broken into small pieces, the lens is then removed by suction through a small tube. Phacoemulsification is the most commonly employed method of cataract removal and is preferred, where possible, over cutting into the eye to remove the lens.
After the diseased lens is removed from a dog with a cataract, an implant is placed in the eye to replace the lens.
Before surgery for a cataract is performed, your veterinarian may recommend an electroretinogram to ascertain whether the retina is functional. An ultrasound of the eye may also be needed to rule out the possibility of retinal detachment. If the retina is not functional, the eye will be functionally blind even with the cataract removed and cataract surgery may not provide any benefit for your dog.
Cataracts are common in senior dogs but can occur for various reasons in dogs of any age. Cataracts may involve both eyes and may cover the entire lens, resulting in blindness for your dog. Surgical options exist which can restore the canine eyesight if the retina is functional and the eye is otherwise healthy.
Reprinted with permission from Pet Health Care Gazette (http://www.pet-health-care-gazette.com/2012/01/23/cataracts-in-dogs/)