What are cataracts?
A cataract is any opacity or loss of transparency of the lens of the eye. The opacity may be confined to a small area of the lens or capsule, or it may affect the whole structure. A complete cataract affecting both eyes will result in blindness, whereas small non-progressive cataracts will not interfere with vision. Primary cataracts occur in some breeds; in other breeds the cataract may develop secondarily to another inherited disorder such as progressive retinal atrophy or glaucoma.
Most cataracts are inherited. Non-hereditary cataracts also occur, as a result of other diseases, trauma, toxicity, or metabolic disturbances.
How are cataracts inherited?
The genetics have not yet been defined for most affected breeds. In others, the mode of inheritance is autosomal recessive, autosomal dominant, or with incomplete dominance.
What breeds are affected by cataracts?
As you can see from the following list, inherited cataracts have been identified in many breeds. In general, the age of onset, the ophthalmoscopic abnormalities seen, the rate of progression, and the degree of symmetry are specific to each breed. Congenital cataracts are those that are present when the eyes open or before 8 weeks of age; juvenile or developmental cataracts occur in young animals up to about 4 years of age; and later onset cataracts develop in mature animals.
Afghan hound (early developing cataracts progressing to visual impairment by 2 - 3 years of age), akita (cataracts associated with microphthalmia), Alaskan malamute (juvenile), American cocker spaniel (juvenile), Australian cattle dog (blue heeler), Australian shepherd (congenital, juvenile, adult), Basenji (congenital), beagle (congenital), bearded collie (juvenile, adult), Bedlington terrier (juvenile), Belgian sheepdog (cataracts non-progressive, do not cause visual impairment), Belgian tervuren (non-progressive, do not cause visual impairment), Bichon frise (juvenile), border collie (adult), Boston terrier (early onset cataracts, bilateral, progress to complete cataract and blindness by 2 - 3 years of age, and later onset cataracts, only occasionally interfere with vision, seen before 8 years of age), Bouvier des Flandres (congenital, juvenile, adult), Brussels griffon (adult), Cavalier King Charles spaniel (early onset cataracts appear by 6 months, progress to complete cataract and blindness by 2 years), Chesapeake Bay retriever (cataracts seen as young adult, may progress to impair vision), chow chow (congenital cataracts), Clumber spaniel, collie (rough and smooth - congenital), curly-coated retriever (cataracts develop as adults and progress slowly), dachshund , dalmatian , Doberman pinscher (cataracts develop before 2 years of age and may cause significant vision loss), English cocker spaniel (juvenile), English springer spaniel (congenital, juvenile, adult), German shepherd (congenital or early developing cataracts that are non-progressive after 1 or 2 years of age), German short-haired pointer (juvenile), Golden retriever (cataracts develop at varying ages, and at different lens locations, usually without visual impairment), Gordon setter (juvenile or adult), Great Dane (juvenile), Havanese, Irish setter (juvenile), Irish wolfhound (juvenile, adult), Italian greyhound (juvenile), Jack Russell terrier, Japanese chin, Labrador retriever (mostly see stationary or very slowly progressive cataracts by 1 to 3 years of age, that do not interfere with vision), Lhasa apso (adult), Lowchen, Mastiff, miniature schnauzer (congenital, juvenile, adult, also cataracts in association with microphthalmos), Newfoundland, Norbottenspets, Norwegian elkhound (juvenile), Nova Scotia duck tolling retriever, Old English sheepdog (congenital, juvenile, adult), Papillon (juvenile, adult), Pekingese, Pembroke Welsh corgi (congenital, juvenile), Portuguese water dog, rottweiler (juvenile, adult), Saint Bernard (juvenile), samoyed (congenital, juvenile, adult), Scottish terrier (adult), Shar Pei, Shetland sheepdog, Shih tzu, Siberian husky (juvenile), smooth fox terrier, soft-coated Wheaten terrier, Staffordshire bull terrier (early onset cataracts are seen by 12 months and progress to blindness by 3 years of age), standard poodle (cataracts are bilateral, symmetrical, and progressive to blindness by about 2 years of age), standard schnauzer (juvenile), Tibetan spaniel, Tibetan terrier (juvenile), Welsh springer spaniel (cataracts develop as early as 8 to 12 weeks of age and progress rapidly, impairing vision), West Highland White terrier (congenital, juvenile), whippet (adult), wire-haired fox terrier (juvenile), Yorkshire terrier (juvenile)
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
What do cataracts mean to your dog & you?
This depends on whether the cataracts are localized to a small area or are more general, and whether they affect one or both eyes. A small cataract in one eye will not affect your dog's vision at all. At the other end of the spectrum, cataracts may progress rapidly or slowly to cause complete blindness.
Congenital cataracts or those that develop at a young age may mature and be reabsorbed, resulting in improved vision. This is unpredictable. In the process of resorption, liquefied lens material may leak into the eye causing inflammation and possibly glaucoma.
With their acute senses of smell and hearing, dogs can compensate very well for visual difficulties, particularly in familiar surroundings. In fact owners may be unaware of the extent of vision loss. You can help your visually impaired dog by developing regular routes for exercise, maintaining your dog's surroundings as constant as possible, introducing any necessary changes gradually, and being patient with your dog.
How are cataracts diagnosed?
You may suspect your dog is having visual difficulties and/or you may notice discoloration of your dog's pupil(s). Your veterinarian will be able to see the cataract with an ophthalmoscope. Even when not causing visual problems, cataracts may be discovered on a routine ophthalmoscopic exam.
How are cataracts treated?
Cataracts can be removed surgically. The decision whether to do so is based on several factors, such as whether the cataracts are progressive, the degree of visual impairment, and the dog's temperament. To prevent postoperative problems, the dog must be cooperative and quiet, especially in the first week following surgery.
It is prudent to assume cataracts are inherited unless another specific cause can be identified. Since some cataracts cause no clinical signs, it is worthwhile to screen dogs of affected breeds annually that are used in breeding programmes. Where cataracts are identified, affected animals, their parents and littermates should not be used for breeding.
The fact that the age of onset is fairly specific for different breeds is helpful in making decisions about breeding programmes.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Where to find more information?
American College of Veterinary Ophthalmologists. 1996. Ocular Disorders Presumed to be Inherited in Purebred Dogs. Purdue University, W. Lafayette, Indiana.
Copyright © 1998 Canine Inherited Disorders Database. All rights reserved.
Revised: December 29, 2004.