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Our Library of Dog Health Articles - Eye Disorders in Dogs

History tells us that we now live longer than ever before and so do our dogs. Scientific and veterinary advances have ensured that many illnesses have been successfully eliminated and newer therapies are being discovered to deal with existing illnesses.  But it’s not all good news – the occurrences of age related illnesses in dogs is rising and we need to deal with these age-related disorders like cataracts as best we can. To be able to do this, we need to know exactly how ageing works.

Your vet will use a grading system from 1 to 6 to describe how loud the murmur is e.g. a grade 1 murmur is very soft and a grade 6 murmur is very loud. You should ask your Vet for this assessment.

Cataracts in dogs are a common and  a predominantly age related disease in dogs

There are two main ageing processes that take place in the dog’s eye, oxidation and glaucation and both lead to the proteins in the lens becoming damaged and resulting in a cataract.   

Most researchers agree that a major factor involved in ageing is damage caused by free radicals.  Free radicals are very unstable and will react with molecules in the body causing damage by oxidation. We carry inside us a variety of antioxidants, natural chemicals which mop up free radicals and destroy them, keeping damage low. The problem is, with the passage of time, the amount of these antioxidants reduces, and so we become unable to fight free radicals effectively. In this way, age-related damage accumulates leading to cataracts.

Another important cause of ageing is glycation where molecules such as sugar, aldehydes, and ketones present throughout the body may attach themselves onto proteins. This glycated protein then becomes capable of irreversibly bonding or “cross-linking” to other proteins to form AGE’s (advanced glycation end products). These AGE’s disrupt normal cell function

The combined effect of  oxidation and glycation is that damaged protein molecules in the lens loose their clarity  resulting in the milky opaque

Why are Cataracts in dogs so often linked to diabetes

As we  discussed further up the page, one of the principle factors contributing to cataracts is what we call glycation of the proteins in the lens of the eye. Glycation explained simply means that sugar molecules become attached to the protein molecules.

This glycation process is more active in dogs that have diabetes and goes some way to explaining why cataracts are more common in dogs with diabetes.

Dry-eye disorders in dogs

As the name implies, this refers to problems with the tear film leading to drying and increased exposure of the ocular surface. You can have a decrease in the amount of tears produced (KCS – keratoconjunctivitis sicca) or problems with the quality of the tear film.

Normal tears spread across the surface of the eye and maintain a stable film. Problems occur when the tears bead like water on a freshly waxed surface. This results in drying of the surface of the eye.

Dry-eye disorders are important for a few reasons. First, dry eyes are uncomfortable. Secondly, tears are very important to the health of the cornea. The cornea is the “windshield” portion of the eye. One of the reasons it is transparent is because there are no blood vessels within the cornea.

Tears provide a large part of the oxygen and nutrients to the cornea. Decreases in tear volume or quality leads to corneal starvation. This, in turn, results in the surface of the cornea becoming more skinlike as a protective response (similar to a callous), which can appear hazy or cloudy. These changes can lead to vision loss over time.

The cornea can develop open sores (corneal ulcers), and these are much more susceptible to infection in dry-eye disorders and can be disastrous to the eye.

Many times the first sign of a dry-eye condition is increased mucous – the eye attempting to lubricate in response to the drying.

Glaucoma in dogs

This occurs when pressure inside the eye increases and damages the optic nerve and retina, leading to vision loss.

Fluid is continually produced inside the eye, behind the pupil. This fluid flows forward through the pupil into the front of the eye, where it fills the space between the cornea and iris. This then flows continually out of the eye through a drain into the bloodstream.

Glaucoma occurs when this drain gets plugged, making outflow slower. Anything that plugs up the drain can lead to glaucoma though, including tumors in the eye, previous trauma to an eye, long-standing cataracts (causes inflammation and scarring in the drain). So senior dogs have a higher incidence of glaucoma than younger dogs.

Signs of glaucoma include increased cloudiness (of the cornea, so it would look like the whole eye is

cloudy, not just the pupil), bulging appearance to the eye or bloodshot appearance to the white of

the eye.

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