What is a cataract? A cataract is a disorder that affects the lens of the eye in which the lens becomes progressively cloudier. Cataracts cause blurred vision and eventually, when the entire lens becomes cloudy, they can cause blindness. Cataracts are not usually directly painful but the loss of vision and eventual blindness can cause confusion and possibly anxiety in dogs and may make them more prone to injury.
But when it comes to miniature schnauzers, these cataracts can be seen as early as 8 weeks in life, with more obvious changes occurring by 4 months of age, and they can affect both eyes. Owners may not recognise the problem or seek veterinary advice early on until the symptoms progress. Cataracts can be associated with other conditions, such as persistent inflammation of the eye or increased fluid pressure within the eyeball, both of which are painful and can cause permanent damage and irreversible vision loss. Large cataracts or those with complications can be removed via surgery to improve the quality of life for the dog.
In miniature schnauzers, cataracts can be due to genetics. A recessive mutation causing cataracts means that two copies of the gene are needed for dogs to be affected, and that dogs which only have one copy are not affected but they may pass the gene to their offspring.
Cataracts are the leading cause of blindness in dogs. There are several stages of cataracts – incipient (in which there is mild blurring to the lens), immature (in which vision is obstructed), mature (the entire lens is cloudy/opaque) and hypermature (in which the lens is shrunken in size). Early diagnosis and treatment of this condition is recommended.
As they become formed, cataracts are easily identifiable by a cloudy or blueish-grey mass in the dog’s eye, and an examination of the eye by a veterinary surgeon will confirm the presence of a cataract. In older dogs, cataracts must be distinguished from nuclear sclerosis, which is the natural change of the lens density in ageing animals and which does not substantially affect vision.
An autosomal recessive mutation is responsible for early-onset cataract development in this breed. However, the specific gene involved has not yet been identified.
As of this moment, DNA testing isn't currently available for hereditary cataracts in Miniature schnauzers, and further research is need to identify the genetic nature of the condition. It is recommended to regularly get dogs’ eyes checked by a veterinarian from 6 months.
For early-onset cataracts, where a simple mutation of a single gene is responsible, a screening program could be developed to help eliminate the problem. In the interim, it is not advisable to breed from affected dogs or from dogs of predisposed breeds with affected relatives, including grandparents, siblings, previous offspring and siblings of parents.
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