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  Cataracts

 

Common names or abbreviations:

Cataracts

Description or definition:

A cataract is a cloudiness to the lens of the eye that causes light to scatter as it enters the eye. The scatter of light may initially only result in blurry vision, but may eventually progress to cause blindness. The opacities can range from minute areas that are barely detectable to complete cataracts in which the lens suffers a total loss of light transmission, resulting in blindness.  There are many causes of cataracts including: genetic conditions, aging degeneration, birth defects, diabetes, nutritional, electric shock, and trauma.  They can also be secondary symptoms to other eye diseases. Heritable cataracts are noted in younger animals (as early as 6 months up to 6 years of age) and affected individuals should be removed from a breeding program and neutered as they may pass the defective gene on to future generations. Older dogs, just as older people may also develop cataracts as an aging degeneration.  Cataracts will also develop in all dogs afflicted with diabetes.
 

In some dogs with diabetes, cataracts may have a rapid onset causing acute blindness. In others, cataract formation may be slowly progressive. Proper control of the diabetes will aid in slowing the onset of cataracts. Electric shock, like from biting electrical cords or lighting strike may also result in cataract formation. These will rarely cause visual impairment. Traumatic injuries to the eye may also result in secondary cataract formation. Traumatic injuries may include a blunt blow to the eye or penetrating injury like from a scratch or thorn.

 

General Information

If cataracts are extensive and bilateral, total blindness results. Cataracts in dogs can arise from a variety of causes such as inherited defects in lens metabolism, trauma, nutritional deficiencies, diabetes mellitus, retinal degeneration, or spontaneous developmental abnormalities. They may be acquired or congenital.
 

The exact cause of a cataract observed in an individual dog is often difficult to determine. Congenital cataracts may or may not be inherited. Cataracts may be primary or secondary. Primary cataracts are the type observed when no other ocular abnormality is present. Secondary cataracts are those that are associated with or accompany another eye disorder, such as generalized Progressive Retinal Atrophy (PRA). Genetic cataracts in dogs may be either inherited in a dominant or recessive mode, or both.
 

Genetic factors are the most important cause of cataracts in the dog. The age of onset, initial appearance, and rate of a cataract's progression are often predictable for a given breed. The specific pathogenesis (mechanism) of inheritable cataracts in dogs has not been defined, but likely results from a variety of different defects in lens cellular metabolism.

 

Congenital vs. Non-Congenital Cataracts

Two categories represent the ages at which heritable eye diseases first become apparent: congenital problems (problems that are present at birth) and disorders that occur later in life. Not all congenital eye diseases are heritable; congenital diseases, therefore, do not necessarily indicate defective genes in a line of dogs.
 

Two characteristics typical of many heritable ocular disorders are late onset and the presence of carriers. Many heritable eye problems are not apparent until the animal is middle-aged, between 5 and 9 years old.  Consequently, prospective pet owners are unable to detect a problem when obtaining a puppy. For the same reason, it is difficult for dog breeders to choose breed stock that is free from potentially heritable ocular disease.
 

Occasionally a dog or some of its litter mates have signs of a heritable eye disease, although the sire and dam appear normal. In this situation, the parents are considered carriers of the disease. All of the siblings should be considered carriers as well, unless test matings indicate otherwise. The most prudent and appropriate approach is for those presumed carriers to not be used in a breeding program.

 

Secondary Cataracts

A secondary cataract, for example those occurring secondary to progressive retinal atrophy, may begin as a cortical type, often posterior with typical appearance of vacuoles (clear spaces) arranged in a wedge-shaped area from the periphery of the lens. These are progressive and ultimately mature to total opacity, thus not allowing examination of the retina for presence of retinopathy (retinal disease).

 

Links to sites about this disease:

bullethttp://www.pettribune.com/2000/070100/feature.html
bullethttp://www.petdiabetes.com/pecataracts.html
bullethttp://www.newfdogclub.org/GEN/health_longevity/hl_docs/hhl_2_cataract.htm
bullethttp://cvm.msu.edu/courses/AP/Casey/Canine%20Cataracts.doc
bullethttp://www.grrcny.org/FORMS/cararacts%20and%20vision.pdf
bullethttp://ebiz.hibernia.com/animalclinic/cataracts/

 

This summary provided by:

bulletDebbie Knatz
bulletShepherd's Ridge

 

Dedicated to improving the health of ISSR Shiloh Shepherds.

 

 


Copyright © 1998 - 2009. Shiloh Shepherd Dog™ Club of America.
All rights reserved. Revised: January 2008

The information on this website was written by ISSR breeders and other concerned individuals, however we are are NOT veterinarians. This information is being provided as a general overview, from information we were able to find about each disease through our own research. These summaries are not intended to be relied upon as medical or veterinary advice, nor do we consider ourselves experts in the veterinary field or in any of these conditions. While we do our best to provide the most up to date information, new research is constantly being done on these diseases. We recommend that you do further study and talk to your veterinarian on any topics you see here, as we cannot guarantee that the information posted here is the most current information available.  This site was originally designed and maintained by Debbie Knatz.