What is a cataract? 

A cataract in dogs is very similar to humans.  The lens at the front of the eye normally focuses images on the retina which acts as a screen at the back of the eye.  A cloudy or opaque lens is called a catarct.  This causes less light to reach the screen and for the image to become blurry.

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What causes cataracts?

There are multiple causes of cataracts in dogs.  Injury or general illnes such are diabetes are the common secondary causes (unrelated to the eye itself).  The most common primary cause is old age.  As the eye ages it may not be able to repair damaged lens protein fibers as well, causing opacity. 

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Cataracts are often inherited and therefore propagated through complex genetics.   Dog breeds that are more likely to develop cataracts include the American Cocker Spaniel, Labrador Retriever, French Poodle, Boston Terrier and the Welsh Springer Spaniel.  Cataracts are not uncommon in the Entlebucher.

 

Inherited cataracts may be present at birth (congenital) or developmental.  Some develop early, are obvious at a year of age and cause blindness by the age of two or three.  Others develop over longer periods of time  Developmental cataracts primarily affect the lens cortex, such as posterior polar cataract. Small posterior polar cataract changes do not affect the dog's vision notably, and may progress only to a limited extent. However, even posterior polar cataracts may in some cases progress to affect the whole lens. Both dominant and recessive modes of inheritance exist in breeds where genetics are known.

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Symptoms

Cataracts can affect one or both eyes.  Sometimes, the eye appears cloudy or reflective.  Often  owners will not notice a change until an eye exam is performed.   You may notice your dog bumping into furniture or appearing lost or confused as their vision declines.

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Nuclear Sclerosis

What appears to be lens clouding may actually be nuclear sclerosis, a normal, age-related, hardening of the lens fibers.  The eye may appear cloudy but vision remains good.

 

Disease Progression

If cataracts occupy less than 30% of the lens or if only one eye is affected, they rarely cause complete vision loss. When the opacity covers about 60% of the total lens area, visual impairment becomes apparent. If the opacity progresses to 100% of the lens, the dog will be blind in the affected eye.

 

Progression of the cataract varies depending on type.

• Cataracts may also be described as incipient, immature, mature, and hypermature.

• Incipient – so small it often requires magnification to diagnose. These involve less than 15% of the lens and cause no visual deficits.

• Immature – involves greater than 15% of the lens and often involves multiple layers of the lens or different areas. The retina can still be seen during examination and visual deficits are typically mild.

• Mature – involve the entire lens and the retina cannot be seen during examination. Visual deficits are often significant with blindness or near-blindness often observed.

• Hypermature – the lens begins to shrink and the lens capsule appears wrinkled. Lens-induced uveitis (inflammation within the eye) often occurs at this stage.

 

Treatment

 

No topical medications or drops will delay cataract progression.  Veterinary ophthalmologists may be able to surgically remove the cataract, replace the lens and restore vision if the rest of the eye is healthy. With a successful surgery, your dog will return to normal activity, running and playing within just a few days. 

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Prevention

Unfortunately, eye surgery is very expensive and is prohibitive for many pet owners.  The only way to prevent cataracts is to require regular eye exams of breeding dogs and exclude any affected dogs from the breeding group.

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Long Term Outcomes

Without surgery, the dog will gradually lose vision.  Many dogs adapt very well in terms of navigating their environment but they may have increased anxiety especially in new situations.  Some dogs with mature cataracts go on to develop glaucoma, which is a very painful disease of the eye.   Read more about glaucoma.