Pet Vet: Hound’s blue-tinged eyes a sign of vision problems

July 20, 2014

Alan has a 9-year-old Basset hound named Hank who seems to be having trouble seeing. Over the past three months or so Hank seems tentative when walking, especially in unfamiliar areas. The problem seems worse at night. When Alan has looked at Hank’s eyes, he has noticed a blue color and wondered if this might be a cataract.

Alan, I thank you for the question and especially for the excellent detail you provided about Hank’s condition. First of all it is important to know if the blue color that Alan is seeing is from the outer portion of the eye, the cornea, or deeper within the eye, the lens. If there are no other associated problems with Hank’s eyes, it is not likely to be a corneal problem only because there are usually other symptoms when this structure is involved. Older corneal scarring can leave a bluish cast to the eye, but this has been noticed for only about three months so a corneal disease is less likely.

For this discussion, I am going to assume that the blue color in Hank’s eyes is coming from changes in his lenses within his eyes. The lens in the eye is a very specialized structure, normally clear, that is responsible for focusing what is seen onto the retina. The lens is similar in function to the lens of a camera.

The viewed image passes through the lens and, depending on the distance from the eye, the lens changes shape from rounder to more oval or more oval to rounder to focus the image onto the retina in the back of the eye.

As I previously stated, the lens is a very clear structure but there are changes within its structure that can cause a coloring of the tissue. By far the most common color change seen is one from clear to various shades of blue. As Alan mentioned, cataracts are a possibility.

A cataract is any opacity; i.e. decreased "clearness" to the lens, which prevents normal vision. When this process within the lens first begins, it is possible to see an area of opacification within the lens, but vision is not usually impaired. The process can stop at any point but is often progressive, eventually rendering the entire lens opaque and preventing vision.

Cataracts can be inherited, as there are certain breeds of dogs that show higher incidence of cataracts including American cocker spaniels, golden retrievers, miniature schnauzers, old English sheepdogs and poodles. Some forms of cataracts can start from birth, called juvenile cataracts, while others develop later in life.

Some cataracts can develop as a secondary result of an underlying disease process. The most common example is cataracts associated with diabetes mellitus. This disease should always be considered and ruled out with any case of diagnosed cataracts in our companions.

Another possible cause of a blue color to the lenses is a process called lenticular sclerosis. This is the gradual age-related hardening of the lens that begins to occur around middle age in virtually all types of companions. It usually starts in the central portion of the lens, which starts to turn a grayish blue. It is not a cataract although is commonly diagnosed, even by veterinarians.

Lenticular sclerosis still allows for vision whereas cataracts often cause blindness. We know in humans with lenticular sclerosis that visual acuity, their ability to focus, is impaired with lenticular sclerosis. These people often wear bifocals. We’ve yet to be able to fit bifocals to our companions.

If you notice your companion’s eyes developing a blue color bring them to your veterinarian for a thorough examination. It is generally very straightforward to diagnose, and as a result, you can discuss treatment options.

In the case of cataracts, your veterinarian can refer you to a board-certified ophthalmologist for specific treatments available. This condition, especially when it occurs in younger to middle-aged companions, is very correctable. Often total vision can be restored. In the case of lenticular sclerosis, there is no treatment. Alas, these companions will likely have to buy their books in large type.




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