What is it?
Cataracts are opacities in the lens of the eye. The lens is a transparent disc which changes shape (via fine muscle control) to focus images onto the retina, where the signal is sent to the brain and interpreted as vision. Cataracts cause a loss in the transparency of the lens. Depending on the breed of the dog and the type of cataract, these opacities may be small and non-progressive, allowing your dog to see around them, causing minor loss of vision. However vision loss may be total if a cataract progresses to a larger size.
Most cataracts have a genetic basis, and will be diagnosed when the dog is young.
- Developmental / Congenital - These cataracts develop before the pup is born, and should be detectable via an opthalmoscopic examination once the pup’s eyes are open, or by at least 8 weeks of age.
- Juvenile / Degenerative - Dogs with these cataracts are born with normal lenses, which then proceed to degenerate over time. They may develop anywhere between 8 weeks and 7 or 8 years of age, depending on the type of cataract (of which there are many), and also the breed of dog involved. Labradors suffer from anterior and posterior subcapsular cataracts, which usually become apparent by 1 – 3 years of age.
- Senile - These are associated with age, and may develop in any dog from the age of 8 or 9 years onwards.
- Disease - Cataracts can be associated with the development of diseases such as diabetes mellitus or those that cause hypocalcemia.
- Trauma or Toxicity
- Nutritional Deficiencies
What are the signs or symptoms?
You may notice your dog starting to bump into things or getting a milky, maybe bluish appearance to their eye.
How is it diagnosed?
A simple ophthalmoscopic examination by your veterinarian will detect cataracts, and often before any visual impairment has been noticed.
How is it treated?
On occasion, a congenital or early juvenile cataract may naturally reabsorb, and vision may improve. Some cataracts may also remain small and similarly require no intervention. However, in many cases the cataracts grow and cause severe vision impairment or blindness, and/or inflammation of the eye possibly leading to other severe eye disorders such as glaucoma or retinal detachment. The only treatment currently available to deal with a cataract is to surgically remove it, and possibly replace the lens with a plastic one. This requires the dog to undergo a general anaesthetic, but providing the eye is otherwise healthy, your dog is fit enough to cope with the anaesthetic and you can keep them quiet post-operatively, the improvement in vision following surgery for hereditary cataracts can be excellent. As some hereditary cataracts can progress quickly and risk further damage to the eye, the prognosis for a good outcome is better if surgery is done early in its development. There are also some practical ways you can help your dog to cope with reduced vision. Dogs have terrific senses of smell and hearing, and this will help them to compensate for visual inadequacies, especially if you keep their environment stable eg don’t move furniture around, keep paths clear of obstacles, and take regular routes when you take them on walks. For some of the non-inherited cataracts, there are preventative measures you can take to reduce the risk of your dog even developing them. Maintaining good balanced nutrition is probably the best thing you can do. This will prevent deficiencies, and also prevent obesity, which is a predisposing factor for the development of diabetes mellitus.
How can I avoid buying a dog with it?
Labradors are not affected by congenital cataracts, and the juvenile cataracts they can develop will generally not impact seriously on vision. Despite the fact that these cataracts are not extreme, it is still not recommended to breed with affected animals. As the cataracts are inherited, screening of the parents of a puppy you are considering purchasing is important. Make sure you obtain copies of certification showing a clear examination under one of the accredited eye schemes for the sire and dam of the puppy. Unfortunately, due to the late onset of symptoms, the sire and dam of your puppy may appear to be clear of the disease until they are well into their best breeding years, so if they were affected, you may not know it soon enough. If you are able to look further back through the pedigree of the parents, then this may improve your chances of detecting any evidence of juvenile cataracts in their lines. Responsible breeders will generally have certification done on their breeding stock on an annual basis. In USA, the Canine Eye Registration Foundation (CERF) can direct you towards members of the American College of Veterinary Ophthalmologists for eye exams. In UK, the British Veterinary Association (BVA) conducts eye exams, and in Australia, contact the Australian Veterinary Association (AVA) for examinations conducted under the Australian Canine Eye Scheme (ACES).