Cataracts

Cataracts are the clouding (opacity) of the lens inside the eye, which results from increased accumulation of proteins in the lens. The lens is the part of the eye that focuses images onto the retina at the back of the eye. It is usually clear, allowing light to pass through it to the retina, however when cataracts develop they prevent some of the light from passing through and so cause blurred vision or even loss of vision.

There are four distinct stages of severity of cataracts:

  • Incipient Cataract: the cataract is only present as one small spot on the lens and vision will be unaffected.
  • Immature Cataract: the cataract covers a large part of the lens and vision will be blurry
  • Mature Cataract: the cataract covers the entire lens and results in complete loss of useful vision
  • Hypermature Cataract: the mature cataract has dehydrated and shrivelled up which can result in clear patches on the lens, so restoring some vision.
    Note: Vision will only be restored if the rest of the eye remains functional
    Note: Hypermature cataracts can cause more damage to the eye. As the lens shrivels up it can cause inflammation (known as Lens-Induced Uveitis or LIU). This inflammation can lead to glaucoma, detachment of the retina and a condition known as Lens Luxation. This is where the lens becomes detached and then floats around inside the eye causing even more damage.

Cataracts are one of the most common eye problems in dogs but there is another common eye condition that is often mistaken for cataracts and it is vital to determine which condition your dog has. Nuclear Sclerosis is a hardening of the lens which results in the lens taking on a bluish-grey appearance, similar to the appearance of cataracts. It is a normal condition developed by older dogs but it doesn’t usually interfere with eyesight and doesn’t usually require medical treatment. Cataracts are far more serious and usually do require treatment. Your vet will be able to tell the difference and will advise if your dog needs medication or surgery.

The main known causes of Cataracts:

      • Hereditary (Inherited Cataracts) – the most common cause and can occur at any time of a dog’s life
        Note: certain breeds have a predisposition to inherited cataracts:
        Miniature poodles, cocker spaniels, miniature schnauzers, golden retrievers, Boston terriers, and Siberian huskies
      • Diabetes – the second most common cause
      • Progressive Retinal Atrophy (PRA)
      • Inflammation of the Uvea (Uveitis)
      • Malnutrition/nutritional deficiencies – in this specific case, the cataracts may improve once the dog is on a proper balanced diet
      • low blood calcium levels (hypocalcemia)
      • exposure to toxins
      • radiation
      • electric shock
      • blunt or penetrating trauma to the eye
      • Finally, some cataracts simply appear for no apparent cause in old age
        Note: age-related cataracts are often small and don’t significantly interfere with the dog’s vision

Symptoms:

      • The most obvious sympton is a change in eye colour to a blue, grey or white
      • Inflammation in or around the eye
      • The dog becomes reluctant to move around on its own
      • The dog may start to bump into walls or furniture

Diagnosis:

As soon as you notice a change in your dog’s eye colour, particularly if it is accompanied by signs of vision loss, such as bumping into furniture or not recognising familiar people approaching, you should take your dog to the vet for examination. The vet will check your dog’s eyesight and may perform some other tests to determine if there is an underlying cause for the development of cataracts, such as diabetes or hypocalcemia:

  • The Schirmer Tear Test – measures the amount of tears your dog’s eye is producing.
  • Eye pressure test – to check for Uveitis or Glaucoma
  • Internal examination of the lens
  • Complete blood count test and urine analysis – to check for diabetes, hypocalcemia or some other underlying condition which may have caused the cataracts to develop

Your vet may then refer your dog to an eye specialist who will carry out more specialised tests on your dogs eyes:

  • Electroretinography – to measure the electrical response of cells in the retina
  • Ophthalmic ultrasounds

These tests will help determine the extent of the damage to the eye and whether cataract surgery is necessary.

Treatment:

There is no known treatment that can repair a lens once a cataract has formed. The only way to rid a dog of cataracts is to remove the lens completely. This, however, is not always necessary, as the cataract may be small and have little or no significant impact on the dog’s vision and quality of life. Your vet will be able to advise whether considering cataract surgery is necessary or advisable.

Even if no surgery is required, the cataract must be monitored regularly by your vet, as it is a progressive condition which can lead to other problems with the eye such as Lens-Induced Uveitis (LIU), and Lens Luxation, which in turn can lead to glaucoma, retinal detachment etc.

Removal of hereditary cataracts is usually very successful, particularly if the surgery is carried out in the early stages of the cataract, but other forms of cataract are often not suitable for surgery. Your vet will advise you if surgery is advisable or not.

Surgical Procedure for the Removal of Cataracts:
To remove the cataract, a small incision is made in the lens capsule (the capsula bag) and an ultrasonic probe is inserted. The probe uses  ultrasonic sound to break up the contents of the lens capsule into small fragments that are then vacuumed away through a small tube. This process is called Phacoemulsification.

Once the cloudy lens has been removed, an artificial lens (Intraocular Lens or IOL) is inserted into the empty lens capsule.

Prognosis/Long Term Outcome of Treatment:

After surgery, your dog will be able to see much better than before, but his/her vision will not be perfect. This is because exact replacement of the dog’s natural lens is impossible, plus some scarring is inevitable which will also reduce the level of vision.

In the future your dog may experience a decrease of vision due to the scarring, secondary glaucoma or retinal detachment. To reduce the risk or minimise the impact of these secondary conditions, anti-inflammatory medication will be given after the surgery. Some dogs will require the anti-inflammatory medication for several weeks following surgery whereas others will require it for several months or even for the rest of their lives.

Note: Once the surgical procedure to remove the cataract has been carried out, your dog will never develop another cataract in that eye.


Further information and recommended reading:

For more detailed information on this condition the following websites are well worth a visit:


Related reading:

Canine Diabetes And Cataracts In Dogs — Can You Stop Your Dog From Going Blind?
An article by Darlene Norris
An unfair fact of life is that most dogs with diabetes will develop cataracts in dogs, usually within a year of being diagnosed. Can natural remedies for dogs protect your diabetic pet’s eyes, while regulating his blood sugar at the same time? Read this article

Note: Please consult your vet before giving your dog any of the natural remedies mentioned in the article. Introducing alternative medication and treatment should always be done under veterinary supervision.

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