Up to 75% of diabetic dogs develop cataracts within a year of diagnosis regardless of how well their diabetes appears to be under control. Cataracts cause cloudy eyes and can lead to sudden blindness. Check your dog’s eyes regularly and talk to your vet early if you notice changes, as surgery may be an option for some dogs to restore their vision.
The lens of your dog’s eye is normally clear, like the glass in a camera, and helps focus light so they can see. A cataract is when that lens becomes cloudy, blocking light and making vision blurry, sometimes even leading to blindness.
Diabetes triggers a process in the lens called the sorbitol pathway. High levels of sugar in the bloodstream are converted into a chemical called sorbitol inside the lens, which draws in water and disrupts the normal lens fibres. This swelling and damage causes the lens to become cloudy, creating a cataract. Dogs have a much more active sorbitol pathway than other animal species, which is why they are more likely to develop cataracts with their diabetes.
Cataracts usually start as a small cloudy spot in the lens and gradually spread across more of the eye. As the cloudy area grows, vision becomes increasingly blurred, until the whole lens is affected and sight is lost. In the final stage, the cataract may start to break down causing proteins from inside the lens to leak into the surrounding fluid of the eye.
Since the lens is enclosed in a capsule before birth, the body’s immune system doesn’t recognise the proteins as belonging to itself and triggers a strong reaction to get rid them. This can cause uveitis (painful inflammation inside the eye), which may lead to serious complications such as glaucoma (increased pressure inside the eye) or retinal detachment (when the vision-sensing layer at the back of the eye pulls away).
The table below explains the common terms you may hear used to describe the different stages of cataracts. These stages help your vet track how the cataract is progressing and what it may mean for your dog’s vision and treatment options.
| Stage | What It Means | Effect on Vision | % of Lens Cloudy |
|---|---|---|---|
| Incipient | A tiny cloudy spot in the lens | Usually no noticeable effect | < 10% |
| Early Immature | Part of the lens is cloudy | Vision blurred but dog can still see | 10–50% |
| Late Immature | Most of the lens is cloudy | Vision very poor | 51–99% |
| Mature | The entire lens is cloudy | Vision lost in that eye | 100% |
| Hypermature | Cataract shrinks or starts breaking down; lens proteins may leak causing inflammation | Vision lost but some may return if the damaged lens is completely re-absorbed; painful complications possible | Lens breaks down (≈ 0% normal structure) |
Cataracts from diabetes can develop and progress very quickly, sometimes within days to weeks of the initial diagnosis. About 75% of diabetic dogs will develop cataracts and become blind within their first year of diagnosis no matter how well their blood sugar levels are controlled.
If your diabetic dog develops cataracts, you may notice:
If the cataracts progress to uveitis, you may notice reddened eyes, squinting, watery discharge, cloudiness in the fluid in the front of the eye, small pupils, light sensitivity, and eye pain. This condition requires medical treatment and monitoring to keep your dog comfortable.
It’s important to know that not all cloudy eyes in older dogs are cataracts. Many senior dogs develop a normal age-related change called lenticular sclerosis (also called nuclear sclerosis) from the build-up of lens fibres over time. This gives the lens a bluish or hazy appearance but rarely affects vision in a meaningful way.
Your vet can help you tell the difference between the two by examining the lens with a special instrument called an ophthalmoscope. Lenticular sclerosis looks more like a uniformly foggy window whereas cataracts look more like cracked glass or crushed ice inside the lens. If it is a cataract, your vet will also be able to stage it based on how much of your dog’s vision is blocked.
While research is ongoing, there are currently no medications, eye drops, or supplements that can prevent cataracts, slow their progression, or reverse them in any species. The only way we can effectively restore vision is performing surgery to remove the damaged lens and then replacing it with an artificial lens.
Surgery has the best chance of success if your dog’s diabetes is well controlled and if the surgery is performed before the cataract becomes too advanced, usually when your dog still has at least 60% of their vision remaining. Waiting too long increases the risk of painful inflammation inside the eye (uveitis) and serious complications such as glaucoma or retinal detachment.
If your dog’s eyes are otherwise healthy, cataract surgery has a high success rate with around 85 to 90% of dogs regaining normal vision afterwards.
Cataract surgery is an advanced procedure that requires specialist training and equipment so your veterinarian will likely refer you to a board-certified veterinary ophthalmologist for evaluation and treatment. In most cases, you can expect to pay around NZD $250-350 for the initial consultation. Some cases required additional testing for retinal function (electroretinogram) and retinal detachment (ocular ultrasound), which may cost an additional $800-1000. Cataract surgery roughly costs around NZD $4,700–$7,000 for the surgery depending on whether one or both eyes are treated and based on the individual needs of your dog. This price may also vary depending on the individual ophthalmologist so you may need to request a more accurate cost estimate from your local clinic.
The costs usually cover:
Additional costs may include the referral fee, follow-up visits, and the ongoing use of eye drops for several months after surgery. You will be able to get a more accurate estimate of costs once the specialist has done an initial examination of your dog.
Although the price may seem significant, it reflects the fact that the surgery is performed by a highly trained veterinary ophthalmologist using specialised equipment and that intensive aftercare is needed to give your dog the best chance of success. When compared with the costs of cataract surgery in people, the price for dogs is generally in a similar range because it’s generally a very similar procedure. The main difference with human medicine is that much of the cost of the training, equipment, and surgery is usually subsidised by the public health system or insurance whereas dog owners usually have to pay for the entire surgery themselves.
Cataract surgery is a big decision for any diabetic dog owner. Here we chat with Dr Kellam Bayley, a board-certified veterinary ophthalmologist in New Zealand. Kellam and his partner own Pet Eye Care, an ophthalmology referral service based in Hamilton that treats cases throughout the North Island of New Zealand. More information about his services can be found on the clinic website https://peteyecare.co.nz/. In the following videos, Kellam shares his advice on what owners should think about before making a choice along with practical guidance on the procedure and recovery.
Choosing not to pursue cataract surgery doesn’t make you a bad owner and it doesn’t mean that you love your dog less than owners who do go down that route. With good medical care and some simple adjustments at home, most dogs adapt remarkably well to vision loss and can still lead a happy life as long as their eyes remain comfortable and free from pain.
If referral for surgery isn’t an option for your dog or if your dog is not a good surgical candidate, semi-regular monitoring is recommended with your local vets. Many cases do not require any specific eye medication, however some cases will develop inflammation in response to the cataract and may need to be on anti-inflammatory eye drops. If possible, monitoring of the intraocular pressure is useful to check for glaucoma development. Many veterinary clinics are not able to test intraocular pressure as they do not have the required equipment, but this testing is not absolutely necessary.
If your dog is becoming, here are some things you can do around the house to help them safely adapt:
There are currently no medications or supplements that can reverse diabetic cataracts once they have formed – don’t buy any products that claim to do this! There is a drug called Kinostat that has shown promise in preventing the formation of diabetic cataracts by switching off the sorbital pathway, but it is not commercially available and it is unclear whether the drug will ever reach market. Giving diabetic dogs other eye health supplements such as Lanosterol, L-acetyl-Carnatine, or Ocu-GLO® has not been shown to make any meaningful difference in preventing cataracts or slowing cataract progression when they have been tested in experimental research studies, but are unlikely to cause any serious harm.
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