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 and 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 teated?
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.
Breeding advice
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.
