Dogs can get cataracts as a result of ageing, through birth defects, inherited, and by disease, as Vicky Payne explains…
ABOUT: Holistic vet Vicky Payne BVetMed MRCVS is based in East Sussex, and qualified from the Royal Veterinary College in 2001. She uses a range of complementary therapies alongside conventional medicine and surgery.
When I was at vet school, ophthalmology wasn’t my thing. Maybe it was the timing of the lectures, but I often found it hard to stay awake through a slideshow of images of dog’s retinas, which apparently showed all sorts of different diseases, but which all looked the same to me! When I got interested in helping my clients breed healthy dogs, suddenly eyes became much more interesting. Meeting several really enthusiastic ophthalmologists who let me have a peer through their fancy ‘eye scopes’ also made a big difference!
Cataracts are a very common problem for older humans, with 30% of people over 65 having cataracts in one or both eyes. Dogs can also get cataracts as a result of ageing, but there are also congenital cataracts (birth defects), inherited cataracts and cataracts caused by disease processes.
Clients with older dogs often worry that their pet has cataracts as they have noticed that in some lights the once black pupil seems a bluey-grey. This is not a cataract, but an age-related change called nuclear sclerosis and it affects most dogs over the age of eight. The lens produces new fibres throughout your dog’s life and over time this compresses the nucleus in the middle of the lens, making it dense and cloudy. I think of it like layers of clingfilm… the more layers there are, the less clear the film is. The good news is that this change does not impair vision significantly in dogs, though they can struggle a little in very bright or very dim light.
Cataract is a word used for any opacity in the lens. If up to 15% of the lens is affected then vision may not be significantly reduced. I referred a Golden Retriever patient to an ophthalmologist after seeing a small cataract at her annual health check. Her owners reported she was clumsy in bright light. The ophthalmologist confirmed the diagnosis or a hereditary cataract and explained that it only affected the dog in bright light because when the pupil was small, the light was hitting the opaque area. When the pupil was more open the dog could, essentially ‘see around’ her cataract. This patient was already spayed, but congenital cataracts are on of the things eye panellists check for when doing BVA/KC/ISDS eye screening to reduce the risk of passing the problem on to puppies.
Age-related cataracts affect almost all dogs over 13 years old and become more common in dogs over 9 years old. They can develop from advanced nuclear sclerosis. They develop slowly over months and may take a long time to cause significant vision loss so most vets will have a story like this one… Poppy’s owners were very distressed when they came to see me because she had gone blind overnight and was bumping into all the furniture. They have spent the evening Googling and had come up with some pretty catastrophic diagnoses, including lens luxation and brain tumours. I looked at Poppy’s eyes and asked if anything had changed at home. “Yes!” exclaimed Poppy’s mum, “We had a new sofa delivered yesterday. Oh no, we had the extra stain guard on it, has it poisoned her?” I reassured Poppy’s mum that the new sofa hadn’t poisoned her dog, and that Poppy had actually been blind for some time. Poppy had very advanced cataracts and her eyes looked almost like marbles. Her owners hadn’t noticed as Poppy sported a long floppy fringe. Poppy had gone blind gradually and had learned her way around the house, until the new sofa came and the layout changed. Thankfully, Poppy was able to learn the new layout quickly.
Cataracts can develop rapidly in poorly controlled diabetes where high glucose levels cause water to flood into the lens, after trauma to the eye, as a reaction to some medications, or in cases of lens luxation. If a younger dog develops a cataract your vet will want to ask a lot of questions and may recommend additional tests to find out why the cataract has developed.
Dogs with cataracts should be monitored carefully as the lens changes can cause painful inflammation in the eye (uveitis). If your dog has cataracts and you notice any other changes to the eye such as redness, cloudiness of the surface, or pain you should see your vet as soon as possible.
Cataracts can be removed from dogs at specialist referral centres. Tests are required to make sure the retina is undamaged before surgery as if there is retinal damage the dog may be blind even without the cataract. Surgery is done under general anaesthetic and an ultrasonic probe breaks up the thickened lens in a process called phacoemulsification. The lens material is then removed. Some surgeons place an artificial lens, but if this can’t be done the dog will still be able to see. Cataract surgery gives 90% of dog’s good vision at their one-year check-up, but complications can occur and can be serious. Surgery is most successful if performed before cataracts become hyper mature and cause inflammation in the eye. Surgery for cataracts can cost from £5,000 for two eyes.
If your dog has cataracts and you notice any other changes to the eye such as redness, cloudiness of the surface, or pain you should see your vet as soon as possible.
This article is based on a real cases, but with names and dates changed.