One of the leading causes of blindness in dogs is cataracts. Cataracts are defined as the clouding (opacity) of the lens of the eye. The lens focuses light on the retina to enable vision. Cataracts can therefore impair vision and, if progressive, they can lead to total blindness. Cataracts can develop in one eye (unilateral) or both (bilateral) as a result of the normal aging process, underlying diseases, injury, or be caused by a genetic defect (hereditary cataracts HC).
Two distinct forms of HC are known, the first form, has a very early age of onset. Cataracts occur bilaterally and can be diagnosed as early as 8–12 weeks of age but are not congenital. By 6 months, most of the lens are involved, and defective vision and obvious cataracts occur usually between 9 and 15 months of age with further progression and maturity of the cataract between 2–3 years of age. We refer to this form of HC as “juvenile hereditary cataract” (JHC) to distinguish it from the second type of HC that occurs for which the age of onset is generally 3–6 years. We refer to this later form of HC as “late-onset hereditary cataract” (LHC). Late-onset cataracts may initially occur unilaterally and rarely show bilateral symmetry. In the late-onset form, the cells develop normally, but degenerate later in life, often confused for nuclear sclerosis (normal clouding of the eye due to aging).
A congenital disorder means a problem or disorder that develops or is present in the dog before they are born, and hereditary means something that is inherited, due to the combination of genes that the dog receives from both of their parents.
UNDERSTANDING CATARACTS IN DOGS
Many puppies appear normal at birth, so there is no way to know if the puppy you are buying is going to develop cataracts. Cataracts do not always lead to blindness. In many cases, the puppy or young dog can still see basic shapes, but they may be blurry.
White “cloudy” appearance in the eye
Grey/light blue/abnormal coloration in the eye
Abnormal appearance in light reflection on the eye
Symptoms of vision loss include:
Bumping into door frames/furniture
Barking at inanimate objects
Difficulty finding toys or bowls
TREATMENTS FOR CATARACTS IN DOGS
Providing the cataracts is not bothering your dog by causing severe vision problems, inflammation or advancing rapidly, treatment may not be necessary. Many dogs with cataracts do not worsen and they happily go through their lives with mildly impaired vision.
Surgery is the only option though to restore vision. Ultrasonic waves are used to turn the lens to liquid which is then extracted through a small incision in the eye. Some vets will use a plastic implant to replace the lens. Before any surgical procedure is used, a veterinary ophthalmologist will perform an ERG to make sure the dog's retina is functioning properly. Cataract surgery in dogs is considered a routine ophthalmic operation. The success rate is considered high, at approximately 90% - nine out of ten eyes have a favourable surgical outcome. The success rate is higher in cataracts that have appeared relatively recently than those that are months or years old.
After a cataracts surgery, the pet owner will need to take their dog back to the vets frequently for follow-up care. If all goes well for the first six month period, annual eye checks are then recommended.
Prior to breeding, potential parent dogs can undergo eye screening for congenital hereditary cataracts, The screening should be performed on parent dogs within the twelve months prior to mating-which means that dogs that are bred more than once may have to be tested each time. Eye screening does not guarantee that the dog will not develop congenital hereditary cataracts later in life-which is why dogs may need to undergo screening several times throughout their lives. However, screening prior to breeding and returning a clear result greatly reduces the chances of breeding from dogs that have the condition, and so, helps to breed this fault out of the wider gene pool.