By Dial A Vet Veterinary Team
Many owners first notice a cataract in the evening. The dog hesitates at the back step, misjudges a ball, or the eyes catch the light with a milky white shine. A cataract is a clouding of the lens inside the eye, and as it thickens it blocks light from reaching the retina. Some stay small for years. Others mature within weeks and can cause blindness and painful inflammation if they are left alone. Knowing what you are looking at helps you act at the right time.
Key takeaways
- A cataract is an opacity in the lens. It is different from the soft blue haze of normal ageing, called nuclear sclerosis.
- Cataracts are graded as incipient, immature, mature and hypermature. Vision loss increases with each stage.
- Inherited cataracts and diabetes are the two most common causes in dogs.
- Leaking lens proteins can trigger inflammation inside the eye (lens-induced uveitis), which can lead to glaucoma.
- Surgery by a veterinary ophthalmologist is the only treatment that restores sight.
What a cataract actually is
The lens sits behind the iris and focuses light, a bit like the lens in a camera. It is made of tightly packed proteins arranged so precisely that light passes straight through. When those proteins clump or the lens fibres are damaged, the lens turns opaque. A small cataract looks like a white dot or streak when you shine a torch into the eye. A complete cataract fills the pupil with white, sometimes with a crushed-ice texture.
Cataract or normal ageing?
From about seven years of age, most dogs develop nuclear sclerosis. The centre of the lens hardens and takes on a grey-blue sheen, most obvious in photos or under bright light. Dogs with nuclear sclerosis still see well, and it does not need treatment. A cataract is whiter, often patchy, and interferes with vision. Owners often cannot tell the two apart at home, and that is fine. A vet can do it in a minute with a light and a magnifying lens. If your dog's eyes look blue or grey, our guide on why a dog's eyes look cloudy covers other causes too.
The four stages
- Incipient: a tiny opacity covering less than 15 percent of the lens. Vision is normal.
- Immature: a larger area of cloudiness. Vision is blurred, especially in dim light. This is often the best window to discuss surgery.
- Mature: the whole lens is opaque and the eye is effectively blind, though it may still sense light.
- Hypermature: the lens starts to shrink and liquefy. The capsule may wrinkle, and leaking proteins make inflammation more likely.
Signs to watch for
- A white or milky look in one or both pupils
- Bumping into furniture, especially in a newly arranged room or at night
- Hesitating on stairs, kerbs or when jumping into the car
- Missing thrown toys or treats dropped close by
- Seeming startled when touched from one side
- Red eyes, squinting or a change in eye colour, which can mean inflammation
Why dogs get cataracts
- Inherited: dozens of breeds carry a genetic tendency, including Staffordshire Bull Terriers, Labradors, Golden Retrievers, Miniature Poodles, Cocker Spaniels, Siberian Huskies and Boston Terriers. Some appear in dogs under two years old.
- Diabetes: most diabetic dogs develop cataracts, often within a year of diagnosis and sometimes within weeks. See our page on diabetes in dogs.
- Age: true cataracts become more common in old dogs, alongside nuclear sclerosis.
- Injury or inflammation: a blow to the eye, a penetrating thorn or long-standing uveitis can damage the lens.
- Other causes: low calcium, poor nutrition in very young puppies and some toxins are less common triggers.
When it is urgent
Same day: a red, painful or squinting eye, an eye that looks bigger or bluer than the other, or a sudden change in vision. These can mean uveitis, glaucoma or a dislocated lens, all of which need prompt treatment to save the eye. Our article on glaucoma in dogs explains why speed matters.
Within a week or two: a white spot or cloudy pupil you have only just noticed in a comfortable dog, or a diabetic dog whose eyes are changing.
How vets diagnose and treat cataracts
Your vet will dim the lights, shine a bright light into the eye and look through the pupil, often after dilating drops. They will check eye pressure and look for signs of inflammation. If surgery is a possibility, a referral to a veterinary ophthalmologist follows. The specialist may test retinal function and scan the eye with ultrasound, because surgery only helps if the retina behind the cataract still works.
Surgery uses phacoemulsification, the same technique used in people. The cloudy lens is broken up with ultrasound and removed through a tiny incision, and an artificial lens is usually placed. Success rates in well-chosen dogs are high, often around 85 to 90 percent in published studies, but aftercare is intensive, with eye drops several times a day and regular rechecks.
For dogs that are not surgical candidates, the aim is a comfortable eye. Vets often prescribe anti-inflammatory eye drops to control lens-induced uveitis, and recheck pressure regularly. Many blind dogs live happy lives with a few adjustments, as described in our article on caring for a blind dog.
Can cataracts be prevented?
Inherited cataracts cannot be prevented in an individual dog, but responsible breeders use annual eye examinations and DNA tests where available. For diabetic dogs, steady glucose control may slow progression. Protect eyes from injury and get any red or sore eye checked early.
FAQ
Are cataracts painful for dogs?
The cloudy lens itself is not painful, but the inflammation it can cause is. Squinting, redness or rubbing should be checked promptly.
Will my dog go completely blind?
Not always. Some cataracts stay small for life. Others progress to blindness, which is why regular monitoring matters.
Is my dog too old for surgery?
Age alone is rarely the deciding factor. General health, retinal function and the dog's temperament for aftercare matter more.
Can one eye be done at a time?
Usually both eyes are operated on together when both are affected, but your ophthalmologist will advise.
Talk with a vet
If you have noticed a cloudy eye or your dog is bumping into things, a Dial A Vet veterinarian can help you work out how soon your dog should be seen and what questions to ask. Talk to a Dial A Vet vet online. A red, painful or suddenly blind eye needs an in-person vet the same day.
References
- Merck Veterinary Manual: Cataracts and lens disorders in animals
- American College of Veterinary Ophthalmologists (ACVO): Cataracts owner information
- Gelatt KN, Veterinary Ophthalmology, 6th edition (Wiley-Blackwell)
- Beam S et al. A retrospective cohort study on the development of cataracts in dogs with diabetes mellitus. Veterinary Ophthalmology, 1999
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.
