Hereditary Cataract - HC

 

Overview

HC are an inherited form of cataracts, the most common cause of blindness in dogs. HC are an inherited disease of the lens in a dog’s eye. Essentially it occurs when the clear lens of the eye becomes opaque or white. This interferes with the dog’s vision and puts major strain on the eye resulting in blindness.

According to ophthalmologists, a cataract can occur in varying degrees, it may be the equivalent of a minuscule mark or it may result in total lens opacity. HC may be present at birth or may develop at any age, though early detection is critical in order to prevent progression to a severe stage of visual impairment.

Severity - 3

HC has a moderate ‘degree of severity’, while it is not a fatal disease resulting blindness may decrease the quality of life for both you and your dog.

Symptoms

Affected dogs will show opacity of the lens in their eye when examined; they may also exhibit signs of impaired vision and be unable to focus on small objects such as a ball or toy. n serious cases affected dogs will show signs of severe visual impairment such as failing to avoid objects in their path and have difficulty moving around familiar areas.

While some dogs may not exhibit severe characteristics of visual impairment, they may still be affected by the disease and it may go unnoticed. This can cause complications later in life, as though the disease can be managed through surgery at early stages, sadly there is no cure for blindness in dogs.

Genetic Testing

Animal Network provides a DNA test that determines the genetic predisposition to HC.

HC is autosomal recessive. A direct gene test can determine whether a dog is clear, a carrier or affected. A recessive phenotype (trait or disease) requires two copies of the causative gene variant for the phenotype to be expressed.

If both parents have two copies of the recessive gene variant, then 100% of all offspring will show the phenotype. If one parent has two copies of the recessive gene variant and the other parent is a carrier with a single copy, then 50% of all offspring will show the phenotype and 50% will be carriers. If both parents are carriers of the recessive gene variant then 25% of all offspring will show the phenotype, 50% will be carriers and 25% will be clear. If one parent is a carrier and the other is clear then 50% of offspring will be carriers and 50% will be clear.

Due to the probability of genetic inheritance, the actual outcome of matings may vary from expected ratios, eg 2 carriers may produce all Clear or all Affected.

For an explanation of possible genetic status of offspring please refer to our fact sheet on Breeding Strategies.

There are multiple genes that cause cataracts in dogs – not all forms are hereditary: Australian Shepherds (dominant trait), Boston terrier (Juvenile HC), Staffordshire Bullterrier and French Bulldog. ORDER A TEST

Breeds Affected

Australian Shepherd
Boston Terrier
French Bulldog
Staffordshire Bull Terrier


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