Cataracts

A cataract is an opacity in the lens of the eye. When the lens becomes cloudy, it scatters and blocks light from reaching the retina, causing visual impairment that ranges from mild to complete blindness depending on the size and density of the opacity.

Cataracts in dogs have several causes:

• Hereditary (inherited): The most common cause in young and middle-aged dogs; genetic mutations affect lens protein metabolism. DNA tests exist for some breed-specific hereditary cataracts.
• Diabetic: Rapidly developing cataracts secondary to diabetes mellitus - very common in diabetic dogs; lens glucose metabolism is disrupted.
• Senile (age-related): Gradual opacification in older dogs; a certain degree of lens nuclear sclerosis (bluish haze without true cataract) is normal with ageing and does not significantly impair vision.
• Traumatic: Following eye injury.
• Secondary: Following other eye diseases (uveitis, PRA, glaucoma).

Distinguishing cataracts from nuclear sclerosis

Nuclear sclerosis is the normal age-related bluish-grey haziness seen in older dogs' eyes from approximately seven years onwards. Unlike cataracts, nuclear sclerosis doesn't significantly impair vision - the vet can still see the fundus (back of the eye) through it, and dogs can navigate normally. It doesn't require treatment.

True cataracts appear more opaque and white; vision is impaired. Your vet will differentiate them with an ophthalmoscope.

What to monitor monthly

Lens appearance. Look into your dog's eye in good light. Normal lenses are clear. A white or bluish opacity in the central pupil area is worth having assessed.

Vision. Note whether your dog:

• Hesitates or bumps into objects in unfamiliar environments
• Has difficulty locating toys or food dropped in front of them
• Shows reluctance in low light (cataracts can cause reduced night vision)
• Changes navigation behaviour indoors or outdoors

Pupil and eye response. Note any change in pupil size, any redness around the eye, or any squinting or eye discharge - these can indicate uveitis (inflammation), which is a complication of mature cataracts.

Both eyes. Cataracts are often bilateral (both eyes affected), though asymmetric. Monitor each eye separately.

Stages of cataract development

• Incipient: Small opacity; minimal vision impact
• Immature: Larger opacity; beginning to affect vision
• Mature: Lens completely opaque; significant vision impairment
• Hypermature: Lens protein liquefaction - associated with lens-induced uveitis (LIU), which can cause significant eye pain and secondary glaucoma

Treatment: phacoemulsification

Cataract surgery in dogs - phacoemulsification (the same technique used in humans) - removes the cloudy lens using ultrasound and replaces it with an artificial lens. Success rates are high (>90% regain functional vision) when performed before mature or hypermature stage and without concurrent retinal disease.

Not all dogs with cataracts require surgery - incipient or immature cataracts with preserved vision may be monitored. The decision to operate is made based on the rate of progression, degree of vision impairment, and whether lens-induced uveitis is developing.

If surgery is planned, a pre-surgical electroretinogram (ERG) confirms retinal function is intact - surgery will not restore vision if the retina is not functioning (as in PRA).

Lens-induced uveitis

As cataracts mature, lens proteins leak through the lens capsule and trigger an immune response - lens-induced uveitis. LIU causes eye pain, redness, and, if untreated, can lead to secondary glaucoma and permanent blindness. Dogs with mature or hypermature cataracts should be monitored for redness, squinting, or pain, and seen urgently if these develop. Topical anti-inflammatory drops are used to manage LIU.

When to contact your vet

Contact your vet for a routine appointment if:

• You notice a new white or grey opacity in the eye
• Your dog's vision appears to be changing
• DNA testing or BVA/KC eye scheme assessment is relevant for your breed

Contact your vet promptly if:

• Redness, squinting, eye discharge, or apparent eye pain develops alongside a known cataract - this suggests uveitis or glaucoma
• Vision appears to have suddenly worsened

Frequently Asked Questions

Can cataracts be prevented? Hereditary cataracts can be reduced in prevalence through breeding from DNA-tested clear animals. Diabetic cataracts can be partially managed through tight glucose control, though many diabetic dogs develop cataracts eventually. There is no proven dietary or supplemental prevention.

How much does cataract surgery cost in the UK? Phacoemulsification in the UK typically costs £2,500–£4,500 per eye at specialist ophthalmology centres. Both eyes can sometimes be operated on in one anaesthetic episode. Insurance usually covers hereditary cataracts if the policy was in place before the condition was diagnosed.

My dog has had cataracts for a year and seems fine - do we need to do anything? If the cataracts are small, stable, and your dog's vision appears adequate, monitoring is appropriate. Annual ophthalmology assessments allow tracking of progression. The key trigger for surgical consultation is when cataracts are approaching maturity - before LIU develops.

My diabetic dog is developing cataracts - what are my options? Diabetic cataracts often develop very rapidly (sometimes within weeks of diagnosis) due to the overwhelming effect of high glucose on the lens. Veterinary ophthalmology referral is appropriate. Surgery is effective if the retina is healthy, but diabetic dogs require special perioperative management.

What DNA tests are available for hereditary cataracts? HC (hereditary cataract) DNA tests are available for specific breeds including Miniature Schnauzer, Australian Shepherd, Bichon Frise, Staffordshire Bull Terrier, and others. The HC mutation varies by breed; ensure you use the test appropriate to your dog's breed. Testing is available through commercial veterinary genetics labs and the Kennel Club Health Testing programme.