S.I.G.H.T. Registry (Sealyham Terriers)

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The Sealyham SIGHT Registry Brochure

Sealyham Terriers and Genetic Disease
The Sealyham is a lucky dog, indeed. Owned, bred and loved by a small but devoted number of human beings, the breed is also among the healthiest of purebred dogs. There are very few genetic diseases that affect the breed, and, of those, lens luxation is really the only disease that threatens our dogs and worries us.

What can you do?

• Have an eye exam for your dog every 1-2 years.
• Know the symptoms of lens luxation and the location of the nearest veterinary ophthalmologist in case of emergency.
• Register your dog with the SIGHT registry.

PLEASE REGISTER!!
Every Sealyham Terrier needs to be in the registry so that we can create a full picture of all the breed lines.

What is the SIGHT Registry?
The American Sealyham Terrier Club (ASTC) created SIGHT in 2003 as a registry for the eye health of all Sealyhams. As owners and breeders register their dogs, SIGHT will become an increasingly crucial and comprehensive source of information that will:

• give breeders the ability to reduce the risk of producing affected puppies (read an article on the subject)
• alert owners if new findings indicate that their dogs come from a litter that may be at higher risk for the disease;
• help researchers who are developing a genetic test for lens luxation or studying other aspects of this disease.

Symptoms of Lens Luxation
At this point, we need to assume that almost every Sealham is at some risk for lens luxation. That’s why it’s so important to have your dog’s eyes examined every 1-2 years as a routine preventive health care program. And because the condition can happen suddenly, owners need to be alert to symptoms as well.

Symptoms to watch for (call your vet immediately!!):

• Excessive pus-like matter in the corner of the eye
• Indications of pain or discomfort in the eye
• Changes in the inside appearance of the eye

What is Lens Luxation?
The lens is held in position behind the iris by very fine fibers. If a dog inherits from both parents a copy of the mutated gene that causes lens luxation , there is a very high probability that those fibers, in both eyes, will weaken and break. A dog with the genes for lens luxation may not become affected until the age of 4-8.

The lens at first will move from its normal position (called subluxation). If the fibers break, the lens will slip, or luxate, from position, and may move either forward or backward inside the eye.

When the lens slips from position it often blocks the flow of fluid in the eye, and the resulting rise in pressure may cause glaucoma which will result in irreparable damage to the retina and optic nerve within 72 hours.

If the eye is not damaged by glaucoma, most dogs will still have some vision even with the lens surgically removed. In many cases, the lens in the second eye may be still partially attached, and drug therapy to treat the glaucoma may help to slow the luxation of that lens.

How to Register your dog

1) Eye Exam (optional): You can register your dog without an eye exam. Simply fill out the SIGHT registration form and send it to the registry.

However, we strongly encourage eye exams for Sealys every 1-2 years. You can have your veterinarian do a basic eye exam.

Or you can schedule a CERF (Canine Eye Registration Foundation) eye exam for your dog. This is a standand exam done by any ACVO ophthalmologist (American College of Veterinary Ophthalmologists). ACVO Clinic List (Locate a veterinary opthalmologist in your state) The cost is usually $20-40.

If there is no ophthalmologist in your area, ask your regular veterinarian for an exam. You can register your dog with SIGHTwith a standard veterinary eye exam, but this is not a substitute for a CERF exam by a veterinary ophthalmologist.

2) SIGHT Application Form: If you need a form, click here to download and print. Complete the form and send it in with the fee. If your dog has had an eye exam, ask your vet for a letter stating results of the exam, or if CERF exam, ask for the CERF form, to include with the SIGHT registration form.

3) Registration Cost: The first time you register your dog, the fee is $10. The fee is $5 for subsequent updates of your dog’s eye exams (every 1-2 years). There is no charge for registering a dog affected with lens luxation.

4) Blood Sample: If your dog is affected with lens luxation or closely related to an affected dog (sibling, offspring or parent), it is very important to send a blood sample to the DNA research project at the University of Missouri. For instructions see the SIGHT Blood Sample Submission form.

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How will breeders use the registry to help reduce the risk of lens luxation?

(Download an article on this subject)

The registry will begin to be useful to breeders when significant numbers of closely related dogs are registered.

A breeder who is interested in a dog from a particular family group will be able to create what is known as a genetic pedigree of that group. The genetic pedigree shows clearly where the affected dogs are in the family, and with that knowledge, the breeder can determine which dogs are probably carriers, and what the carrier risk is for other dogs. GDC will provide information, resources and access to canine genetic counselors to help breeders with complex risk assessments and breeding questions.

What is the GDC KinReport™?
The KinReport™ provides information on a dog’s genetic disease screenings, such as exams for lens luxation. The report includes information not only on the dog in question, but on all close relatives also registered in the data base. If enough closely related dogs are registered, the report provides a comprehensive picture of the location of affected and carrier dogs in a family. With that information breeders can make risk assessments about breeding any two dogs.

How does the genetics of lens luxation work?
Researchers believe (but have not proved) that lens luxation is an autosomal recessive trait. The SIGHT registry will help to determine the mode of inheritance, but for making breeding decisions now we should assume the disease involves primarily a single recessive gene. In this case, a dog will only exhibit the trait if it inherits a copy of the gene from each of its parents. Blue eyes in humans, for example, is an autosomal recessive trait.
A dog with one copy of the gene is called a carrier, and will not show the trait. A carrier will always pass along copies of the gene to some its offspring. We know the probabilty for how many puppies in a litter will carry the gene, but we don’t know which individuals are actually carriers.

Without a DNA test, the only way to positively identify a carrier is to breed it to another carrier. When both parents are carriers, some of the puppies will inherit the genes from each parent, and will become affected several years later. Several other puppies will inherit just one copy of the gene and will be carriers. And the remaining puppies will not inherit the gene.

The parents of an affected dog are assumed to be carriers. And all the offspring of an affected dog are assumed to be carriers. If a dog is a carrier, but has many excellent traits, that dog can still be bred, but only under very strict guidelines. The dog must not be bred to another carrier, and all of the dog’s offspring must be presumed to be carriers until proven otherwise, either by a DNA test, or by several test breedings to a known carrier which produce no affecteds. (Due to the long onset time of lens luxation, test breeding may not be practical.)

GDC (Institute for Genetic Disease Control)
PO Box 177, Warner, NH 03278
Tel. 603-456-2350 Email: gdc@conknet.com
www.gdcinstitute.org

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