Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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A cataract is a focal or diffuse opacity in a lens of the eye. 

Cataracts may be :

  • present at birth (congenital) in which case they may be stationary or progressive, OR 
  • acquired during life.

Cataracts are often described according to their stage of development :

  • Incipient : early opacity and there is no visual impairment. Nucelar sclerosis can look similar in old animals
  • Immature : Incomplete opacity, lens swollen and sight is affected. Intraocular pressure may increase due to glaucoma
  • Mature : Lens is totally opaque and the fundus can not be seen on ophthalmoscopy. Clefts visible on the lens suture lines. If bilateral, the animal is blind. Surgical removal advisable if uveitis is not present.
  • Intumescence : Lens swells with increasing risk of uveitis and glaucoma
  • Hypermature : Lens may liquify, vision may improve. Lens shrinks. High risk of uveitis : warning signs to look for include :
    • Injection of ciliary vessels
    • Hypotony
    • Photophobia
    • Miosis


There are many possible causes of cataract including :

  • Hereditary defect 
  • Associated with other congenital developmental defects of the eye, including microphthalmia, persistent pupillary membrane (PPM) and persistent hyaloid artery,
  • Advancing age - senile cataracts are preceded by nuclear sclerosis,
  • Inflammation - for example associated with uveitis
  • Toxic- naphthalene and diosophenol in dogs
  • Trauma - following direct trauma to the lens
  • Radiation exposure - eg following radiotherapy for cancer
  • Secondary to other diseases eg Diabetes mellitus
  • Electrocution - following electrocution


Breed Occurrence
The Basenji dog is pedisposed to develop PPM and so may develop associated cataract.

Other breeds in which inherited cataracts have been reported include :

Afghan , Australian terrier, Boston terrier, Chesapeake Bay retriever, Cocker spaniel, Entelbucher Mountain dog, German Shepherd dog, Golden Retriever, Labrador Retriever, Norwegian Buhund, Old English Sheepdog, Poodle (Miniature and Standard), Rottweiler, Schnauzer (Miniature), Springer Spaniel (Welsh), Staffordshire Bull Terrier, West Highland White terrier  

It is also suspected in the following breeds:

Beagle, Pointer, Toy poodle, Sealyham terrier and wire-haired Fox terrier

Most owners notice either :

  • A change in behaviour such as bumping into objects or missing catching a ball due to poor vision or even blindness. OR
  • White appearance to the eye. Usually the outer part of the lens (the cortex) is affected first, and the central part (the nucleus) later.

Diabetic cataracts can progress very rapidly and mature in 2-4 weeks, but most progress slowly.

Cataracts may also be associated with other ocular diseases such as progressive retinal atrophy. In such cases treating the cataract (eg by removal of the affected lens) will not improve vision.

Cataracts may form secondary to other diseases, and concurrently with other diseases, so a thorough clinical examination is necessary to evaluate the patient for potential complications.

The structure of the lens changes as the cataract matures resulting in leakage of  lens contents into the surrounding aqueous which can result in uveitis or glaucoma.

Lens luxation is another potential complication as the lens swells during cataract development


Diagnosis of cataract is confirmed by direct visual appraisal using a light source or ophthalmoscope


Cataracts may be left in situ providing the animal retains reasonable vision, especially in late-onset senile cataracts

Use of a mydriatic may improve vision in the early stages.

Several surgical procedures can be used to treat cataracts including :

  • Extraction
    • Extracapsular - remove all  the lens except the posterior capsule
    • Intracapsular - remove the entire lens including both capsules
  • Phaecoemulsification - ultrasonic shattering of the lens tissue then removal by irrigation and aspiration
  • Discission - removal of liquid cataracts (young animals) by aspiration through an incision in the anterior capsule

Surgical treatment is sometimes followed by complications.such as uveitis, and retinal detatchment if intracapsular extraction has been done.

Following extraction it is possible to replace the totally removed lens with a synthetic replacement lens. Intraocular lenses of 40D power are used in dogs.

Cataract surgery should not be performed in the following patients:

  • The affected eye is blind for other reasons than the cataract eg concurrent retinal disease - may require electroretinography to rule out this possibility, not just a positive pupillary light reflex
  • Patients with active uveitis


The prognosis can be good for untreated, slowly progressive cataracts, and many animals do not go on to develop serious impairment of vision or blindness during their lifetime 

The prognosis can be good for animals subject to surgery.

Long term problems

Long term problems in untreated patients include the risk of secondary uveitis and glaucoma

Long term problems in surgically treated patients include residual visual impairement or blindness due to post-operative complications, such as retinal detachment


Updated January 2016