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Addison's Project

Initial project description

2004 update on project

BCCA Specialty Eye Clinic, 1996
By Thomas Miller, DVM, MS, DAVCO
Beardie Bulletin, November 1996

[I was pleased to meet and with Dr. Tom Miller at the Specialty in Orlando. Dr. Miller received his veterinary degree from University of Guelpb in Ontario, Canada and additional training to achieve ophthalmology certification from the University of Florida in Gainesville. He practices veterinary ophthalmology in Largo, Florida. This was the first Specialty (Ed note: correction - this was the second specialty) at which CERF screening was offered-thanks to the Bearded Collie Club of Central Florida. I suggested that Dr. Miller write an educational article for us about the most frequent eye problems in Beardies (per CERF research reports) and the one that was found to be most prevalent at the screening clinic. I encourage everyone to read thoughtfully what follows in the interest of prompting the best possible health for our beloved Beardies. Elsa Sell, BCCA Health Chairperson]

I would like to thank the BCCA for the opportunity to administer an eye clinic at your National Specialty in Orlando. I enjoyed the show and its activities and meeting some of your members and their dogs. The predominant eye problem in the breed and at the clinic % was cataracts, so I have prepared a section on lens anatomy and terminology used to describe these abnormalities to accompany a description of the problem.

Anatomy of the Lens
Cataracts are opacities within the lens of the eye. Cataracts are classified by the age of onset, location within the lens, or cause. The lens is shaped like a magnifying glass or an M&M (i.e., both sides are convex). The lens is encased in a cellophane-like capsule which covers it like the coating of an M&M. The lens itself is made up of tiny lens fibers, which are arranged in layers, like an onion or tree rings. Like a tree, new fibers grow around the outside portion of the lens. The fibers you are born with (the center of the lens) is termed the nucleus. The new fibers that are produced after birth (the outer layers) are termed the cortex. Each individual fiber reaches only halfway around the lens. The fibers are highly organized, so that the end-to-end junctions of the fibers are aligned with each other. This creates a "suture line", which is visible on the slit-lamp examination. The suture pattern typically is Y-shaped, upright in the front and inverted in the back, hence the term.

With aging the new lens fibers growing around the outside of the lens tend to compress the central nucleus, creating a "hardening" called nuclear sclerosis. This process is responsible for the blue hazing that is seen in the pupil of all dogs as they reach 8-10 years of age. This haze is different from cataract formation, except with extreme old age.

Causes of Cataracts
Cataracts can be caused by trauma, metabolic disease (such as diabetes), nutritional imbalance, or they can be inherited. The vast majority of cataracts encountered are inherited. The exact mode of inheritance is unknown. Traumatic cataracts generally have an accompanying history of injury and other eye abnormalities that go along with trauma. Metabolic diseases may be ruled out by blood testing. Nutritional cataracts are most often seen in dogs raised on milk replacer, or in pups from large litters who have received bottle supplementation. These cataracts have a typical pattern. They form early in life and usually do not progress after the pup is weaned to solid food. Cataracts of a nutritional cause are like the rings of a tree which can indicate year(s) of drought. An opaque cortex is formed around the nucleus and a normal clear cortex forms over the underlying opaque cortical region. This creates a ring-cataract around the nucleus. This appearance is distinct from inherited cataracts.

Anatomic Location and Size of Cataracts
On the CERF form, cataracts are separated into those that occur in the anterior cortex (those occurring in front of the nucleus), the posterior cortex (the cortex behind the nucleus), the equatorial cortex (around the lens periphery), or within the nucleus itself. Cataracts that involve the suture lines are separated into anterior or posterior suture line cataracts. All cataracts are further described by size. Punctate indicates small, focal cataracts. Intermediate describes those involving a larger area of the lens than punctate. Diffuse cataracts refer to those involving an entire area. Generalized cataracts involve all areas of the lens.

Therefore, most cataracts are described by both size and location. It is possible to have more than one type of cataract in a lens. An example would be a punctate anterior cortex cataract and an intermediate posterior cortex cataract. It is also very important to understand that a cataract can change over time; an example, would be progression from a punctate cataract to an intermediate and eventually a diffuse or generalized one.

Inherited Cataracts
The typical inherited cataract of the Beardie is a punctate to intermediate, anterior cortex cataract. These account for nearly two-thirds of the cataracts in Beardies reported to CERF over the last five years. This type of cataract was seen in 7/40 (17.5%) of the Beardies at the 1996 specialty clinic. Punctate to intermediate, posterior suture line cataracts were seen in 8/40 (20%) at the clinic. Although the cataracts of this second type were very small in several of the dogs and may turn out to be nonprogressive in some cases, the findings are worrisome. The worry is because of the fact that some were already intermediate in nature, indicating that progression can occur. Also, the number seen suggests this type of cataract is common within the breed. The majority of dogs with cataracts of either type were in the 2-5 year age range.

What is the Bottom Line?
The dogs examined at the clinic came from all geographic areas of the USA and Canada, thus representing a cross-section of many breeding programs from all areas. In theory, dogs at a National Specialty represent the best breeding stock available. Fifteen of 40 (37.5%) dogs failed to obtain CERF certification due to cataracts. This is an amazing failure rate for a breed that "doesn't have eye problems." CERF statistics indicate the average failure rate is in the range of 5%.

What Do You Do About It?
You can stick your head in the sand and muddle along, maintaining the old belief that Beardies don't have eye problems. This seems to have been the approach of many breeders in the past, as CERF statistics show only a small fraction of dogs (an estimated 2%) are ever examined.

My recommendations include:

  1. You may wish to have a second opinion by another board certified veterinary ophthalmologist if your dog was found to have a cataract at the Specialty clinic.

  2. Check all breeding stock for eye problems.

  3. Check all dogs from litters in which cataracts have been diagnosed, even pets and those already neutered or spayed.

  4. Dogs should be reexamined until they are at least 5 or 6 to identify those who develop cataracts during the high risk 2-5 year period. Early examination at 1 or 2 years of age is useful to rule out retinal folds, early onset progressive retinal atrophy (PRA), and some other problems. However, cataracts can and do develop beyond 1-2 years.

  5. Affected dogs should be removed from your breeding program and they should continue to have eye examinations yearly to document the progress (or not) of the cataract(s).

  6. Your health committee and board need to vigorously pursue development of an open registry for listing dogs who are affected with cataracts so as to document classification, track progression, and hopefully identify the mode of genetic inheritance.

  7. Owners of a dog with cataract(s) should notify the dog's breeder.

  8. Breeders need to become advocates for the open registry process.

 

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