Cataracts in dogs: symptoms, tests and treatment

Overview

The lens sits inside the eye and focuses light onto the retina at the back. A clear lens allows light through. With a cataract, the lens becomes less transparent and light scatters. Clouding may be localised or spread throughout the lens.

An incipient cataract may cover less than 10% of the lens. In a mature cataract, the whole lens, or 100%, is cloudy. Not every cataract progresses to complete clouding. A small opacity that remains localised may have no effect on your dog's vision.

Nuclear sclerosis is different from a cataract. It is age-related compaction of the lens nucleus, often appearing blue-grey. It does not usually cause blindness.

Cataract stages are described as incipient, immature, mature and hypermature. In some congenital cataracts in young animals, the opacity may become smaller as the lens grows. Some vision may then return as the animal matures.

Causes

Inherited susceptibility is the most common cause of cataracts in dogs. The precise inheritance pattern is unknown for most inherited forms. A cataract may be present from birth or develop later. A cataract identified between birth and 8 weeks of age is classified as congenital.

Diabetes is another major cause. High blood glucose causes glucose to accumulate in the lens, where it is converted to sorbitol. Sorbitol draws water into the lens. Swelling damages the lens fibres and causes clouding. Diabetic cataracts can develop rapidly.

Eye injury, inflammation within the eye and retinal degeneration can also lead to cataracts. A nutritional deficiency in a young dog is a rare underlying cause. Cataracts often involve lens proteins clumping together.

Risk factors

Cataracts occur in both young and old dogs. Inherited forms are recognised in breeds including Golden Retrievers, Labrador Retrievers, Miniature Schnauzers, Siberian Huskies and Staffordshire Bull Terriers. Bichon Frises, Havanese and Australian Shepherds are also among the breeds with inherited cataracts.

About 75–80% of dogs develop cataracts within the first year after diabetes is diagnosed. Cataracts can form despite good glucose control. The overall proportion of diabetic dogs affected is also estimated at more than 85%.

Age-related cataracts usually progress more slowly than diabetic cataracts. Inherited cataracts often affect both eyes. Severity may still differ between eyes, so the need for surgery may not be the same in both.

Congenital cataracts in Miniature Schnauzers may be visible as soon as a puppy's eyelids open. Cataracts in young animals progress faster on average than those in older animals.

Typical symptoms

Lens clouding may appear as a milky, white, grey or bluish area in the centre of the eye. A cataract can also look like small spots or white streaks. Reduced vision is not always obvious initially, as your dog can compensate using hearing and smell.

• A new pale opacity is visible inside the eye.
• Your dog bumps into furniture or other obstacles.
• Moving around becomes harder, particularly in dim light.
• The eye no longer reflects light as before in night-time photographs.
• Inflammation causes squinting, watering or redness.

A cataract itself is not usually painful. Pain may arise from associated uveitis or glaucoma, involving raised pressure inside the eye. Rapid vision loss can cause your dog to become withdrawn.

Complications and consequences

Lens-induced uveitis can develop when lens material leaks into surrounding tissues. The lens capsule normally separates lens proteins from the immune system. If the capsule is damaged, the body can mount an inflammatory response against lens material. A diabetic cataract can sometimes even rupture the lens capsule.

Advanced cataracts can make the lens less stable and complicate later surgery. Glaucoma or retinal detachment can develop in an untreated eye with a cataract. In a severe case, the eye may need to be removed to control pain.

Cataract surgery has a success rate of about 90–95% during the first 1–2 years. A success rate of 85–90% is also reported for uncomplicated surgery. Surgical complications may occur in 5–10% of cases. They include inflammation, raised eye pressure and retinal detachment.

In retinal detachment, the light-sensitive retina separates from the tissue beneath it. After surgery, the lens capsule left around the artificial lens may also become cloudy. This is called a secondary cataract. It does not mean the original lens that was removed has grown back.

Dry eye is a common problem after surgery in diabetic dogs. The tear glands then fail to produce enough fluid to maintain corneal health. The condition may require long-term medication.

A dog's eye generally develops a stronger inflammatory response to cataract surgery than a human eye, making intensive aftercare necessary.

Diagnosis at the vet

The vet examines the inside of the eye and assesses the location and extent of clouding. Dilating the pupil helps examine the lens. Slit-lamp examination shows lens structures in detail. Eye pressure is measured with a tonometer when investigating possible glaucoma.

Blood and urine are tested if diabetes or another general illness is suspected. The safety of general anaesthesia is also assessed before planned surgery. Possible preoperative tests include a blood count, blood biochemistry and urinalysis.

Before surgery, retinal function is measured using electroretinography, or ERG. Eye ultrasound looks for problems such as retinal detachment. These tests are useful when the cloudy lens prevents a view of the back of the eye. If the retina does not work, clearing the lens will not restore vision.

Preoperative tests also measure tear production. A dye can check the integrity of the corneal surface. ERG and eye ultrasound often require sedation. The tests complement each other: ERG measures function and ultrasound shows structure.

In some official eye screening schemes, cataracts are generally presumed inherited unless shown to result from a cause such as injury, inflammation or metabolic disease. This assessment affects the breeding report.

Treatment

The vet prescribes treatment based on the eye findings and your dog's general condition. A cloudy lens can be removed surgically, but no eye-drop treatment is known to cure cataracts. Medicines may still be needed to control associated inflammation.

The usual operation is phacoemulsification, in which ultrasound breaks up the lens and suction removes it. The procedure is performed under general anaesthesia. A small incision is made at the front of the eye. A circular opening is created in the lens capsule. An artificial lens may replace the removed lens. This helps focus light onto the retina again.

A cataract does not usually need to become fully mature before surgical assessment. Earlier surgery may reduce problems associated with long-standing cataracts. Both suitable eyes can often be operated on during the same anaesthetic. If only one eye is suitable, treatment can focus on that eye.

A diabetic dog's glucose control is stabilised before anaesthesia and surgery. Skin and dental disease are also treated before planned cataract surgery. Serious general illness, retinal degeneration or uncontrolled dry eye may prevent the procedure.

Initial healing usually takes about 2 weeks. A collar is often needed to protect the eye for about 2–4 weeks. Exercise is restricted, avoiding running, jumping and play with other animals. Outings consist of short, controlled lead walks using a harness.

Eye medicines and repeated follow-up examinations are needed after surgery. The first postoperative check is often at 1–2 weeks. Some medicines are temporary, while others may be needed long term or for life.

If surgery is not performed, inflammation and eye pressure are still monitored. Eye pressure may be checked every 4–6 months, for example. Many dogs manage with reduced vision in a familiar, safe environment.

The ultrasound technique uses a smaller eye incision than older manual lens-removal surgery. The operating time is also shorter. Lens contents can be removed more completely. Eye microsurgery therefore requires a specialised operating microscope and precise instruments.

Your dog's temperament and willingness to allow eye handling also affect the ability to manage recovery care. A calm patient that can be treated is better suited to intensive aftercare.

Hospital monitoring may last 3–4 days. Some dogs go home the day after surgery. Several repeat examinations by a veterinary ophthalmologist are needed during the first year.

Prevention

Inherited or age-related cataracts cannot reliably be prevented with home measures. Eye injuries should be examined promptly, as inflammation can lead to cataracts. A diabetic dog's eyes are monitored even when blood glucose management is going well.

Some breeding schemes generally exclude dogs diagnosed with inherited cataracts from breeding. Exceptions include certain lens changes of little significance, for which breeding with a healthy mate may be allowed. Within such schemes, the validity of an adult dog's official eye examination depends on the breed-specific screening programme.

Some screening schemes treat an official eye examination performed before 1 year of age as valid for no more than 1 year from the report date. If the breed's programme requires an eye report, an expired examination must be repeated before the next mating.

Important for dog owners

Record when the eye's colour or your dog's movement changed. Note whether the problem is more obvious in dim light, on stairs or in unfamiliar surroundings. Mention increased drinking, previous eye injuries and current medicines too. Bring earlier eye examination results and any diabetes monitoring records.

Before deciding on surgery, discuss who will give eye drops, attend follow-up visits and supervise a quiet recovery. Ask what to do if your dog resists drops or the collar. Keep furniture and routes around the home familiar. Do not test vision by forcing your dog onto stairs or to jump over obstacles.

Frequently asked questions

Does a bluish eye in an old dog always mean a cataract?

No. Normal age-related compaction of the lens nucleus, called nuclear sclerosis, can look blue-grey. It does not usually cause blindness. A veterinary eye examination reliably distinguishes this common ageing change from a true cataract and other causes of clouding.

Can cataracts be treated with eye drops?

There is no proven medical treatment to remove cataracts; the cloudy lens is removed surgically. Eye drops may nevertheless be needed to treat inflammation and other complications. Topical eye medicines can therefore also be prescribed for a dog that does not have surgery.

Must a cataract mature before surgery?

No. Surgical assessment is best arranged before complete clouding, as advanced cataracts involve more inflammation within the eye and problems with lens structure. The right timing depends on the eye's current condition and your dog's general health.

Can a diabetic dog develop cataracts despite good care?

Yes. Within the first year, about 75–80% of diabetic dogs develop cataracts even when diabetes is well controlled. Glucose management continues, and the safety of any possible surgery is assessed separately.

Can a dog live well without surgery?

Many dogs adapt to declining vision, particularly when the change is slow and home remains familiar. The eye is still monitored for painful complications. Deciding against surgery does not mean leaving inflammation or raised eye pressure untreated.