Details about the disease
A cataract is an “opacity”, or loss of transparency of the lens of the eye. The opacity may be confined to a small area of the lens, 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.
Clinical signs
Obvious cataracts occur between 9 and 15 months of age with further progression and maturity of the cataract between 2-4 years. This is a blinding condition if left untreated.
How is it inherited?
A number of breeds are known to suffer from HC and there are almost certainly different genetic causes for a number of these. Mutations in one gene called HSF4, has been shown to cause HC in a number of different breeds (Australian Shepherd, Boston Terrier, French Bulldog and Staffordshire Bull Terrier). One of the HSF4 mutations causes bilateral cataracts, in Staffordshire Bull Terriers, Boston Terriers and French Bulldogs, that can be diagnosed as early as 8-12 weeks of age, but are not congenital.
In these breeds the mutation in HSF4 is an autosomal-recessive condition. This means that a dog must inherit two copies of an abnormal gene (one from its mother and one from its father) before its health is affected. A dog that inherits only one copy of the abnormal gene (from its mother or its father) will have no signs of the disease, but will be a carrier and may pass the gene on to any offspring.
A slightly different mutation in the same gene has been identified as a risk factor for bilateral posterior polar subcapsular cataracts in the Australian Shepherd. This form of cataract has quite a variable age of onset and in this breed, the HSF4 mutation appears to behave as an autosomal-dominant condition. This means that a dog must inherit only one copy of an abnormal gene (one from its mother or one from its father) before its health may be affected.
Which laboratories do we record and publish the results from?
To find out which laboratories The Kennel Club is able to record results from, and which laboratories will send results directly to The Kennel Club, please refer to our website.
Please be aware, The Kennel Club has a set of criteria that we request DNA testing laboratories to meet to enable us to record their results, helping to maintain and protect the integrity of results that appear on a dog’s record. We strongly advise that customers ensure their chosen laboratory is included on our list if they wish The Kennel Club to record and publish the results. Results from laboratories not included on this list will not be recorded.
Breeding advice and what your dog's results mean
If, once your dog is DNA tested, you would like to find out what their DNA test results mean, or how to select the right mate to avoid producing affected puppies, then please read our breeding advice and DNA testing information.
For Australian Shepherds, the way that this condition is inherited slightly differently, so please see our read our breeding advice for autosomal-dominant conditions for this breed.
How to find out if a potential mate has been DNA tested
The Kennel Club’s Health Test Results Finder allows you to find the results of DNA tests carried out as part of The Kennel Club's official DNA testing schemes for any dog on The Kennel Club’s Breed Register.