KnD Kennels

Primary Lens Luxation Information
Rat Terriers

"Lens luxation is the dislocation or displacement of the lens within the eye. The lens is the clear structure in the eye, consisting of two rounded or convex surfaces, that focuses light rays to form an image onto the retina. Normally the lens is suspended between the iris (the colored portion of the eye) and the vitreous (the clear gel in the back of the eye), and is held in place by small fibers called zonules or suspensory ligaments.

Should the zonules break, the lens can either become partially dislocated (subluxated) from its normal position or completely dislocated (luxated). When the lens detaches and falls forward into the anterior chamber in front of the pupil, it is called an anterior luxation. When it falls back into the rear portion of the eye, it is called a posterior luxation."

"Primary Primary lens luxation is an inherited disorder in which the zonules or suspensory fibers degenerate. The condition occurs mainly in the terrier breeds, namely the Parson Russell terrier, Tibetan terrier, smooth fox terrier and rat terrier. Primary luxations are also seen in the border collie, the Australian cattle dog (blue heeler), and sporadically in other breeds. Although the underlying reasons for the lens luxation are not well understood, inflammation or a defect in the zonules may play a role. With primary lens luxations, both eyes are prone to dislocation of the lens. "

Until October 15, 2009 there was NO test for PLL. Breeders were having to breed in the dark. But NOW, there is NO excuse. The University of Missouri, College of Veterinary Medicine through the partnership of OFA (Orthopedic Foundation for Animals), now has a DNA test for this mutation.

The DNA test can determine a dogs PLL status as:

AFFECTED- "AFFECTED have 2 mutated copies of the gene. The vast majority of these dogs will luxate at 4-8yrs of age, the typical age of onset for PLL. There were a few dogs in the study group that tested as AFFECTED but did not luxate until after 8 yrs of age, and some dogs testing AFFECTED have died from other causes without luxating. A search of published veterinary literature revealed that about 10% of the dogs reported to be clinically affected with PLL had onset of symptoms after 8 yrs of age. Because of this, the test results will say “AFFECTED/HIGH RISK”.

CARRIER- "Dogs testing CARRIER are at a slight risk of developing PLL. Carriers have one normal and one mutated copy of the gene. They could pass either the normal copy or the mutated copy on to their offspring. Because there were very few cases of dogs in the research groups testing CARRIER who did appear to have PLL, the test results will say “CARRIER/LOW RISK”.

NORMAL- "A dog testing NORMAL has 2 normal copies of the gene, is not at risk for developing PLL, and can only pass a normal copy of the gene to any offspring."

Canine Lens Luxation Basics
Elizabeth A. Giuliano, DVM, MS Diplomate, American College of Veterinary Ophthalmologists Assistant Professor, University of Missouri, College of Veterinary Medicine

Dogs that have been determined as carriers and normal can be bred safely:

Breeding Strategies
Autosomal Recessive Diseases

*Clear/Normal; "This finding indicates that the gene is not present in your dog. Therefore, when used for breeding, a Clear dog will not pass on the disease gene."

Carrier: "This finding indicates that one copy of the disease gene is present in your dog, but that it will not exhibit disease symptoms. Carriers will not have medical problems as a result. Dogs with Carrier status can be enjoyed without the fear of developing medical problems but will pass on the disease gene 50% of the time."

Affected: "This finding indicates that two copies of the disease gene are present in the dog. Unfortunately, the dog will be medically affected by the disease. Appropriate treatment should be pursued by consulting a veterinarian."

* Please Note: Some sites and some breeders use the word Normal or Clear. Both these words mean the same thing. It means that the dog in question is NOT a Carrier nor is it Affected.

You will see on KnD's health clearances the wording "Cleared By Parentage" or "CBP". This means both sire and dam are proven Normal/Clear and that pair bred together can never produce an affected or a carrier.

Understanding Autosomal Recessive Traits Like PLL HERE

Helpful Canine Breeding Chart
Autosomal Recessive Diseases

"The chart provided below outlines the implications of various breeding pair combinations. Remember, it is always best to breed "Clear to Clear". If followed by all breeders, these strategies will ensure a significant reduction in the frequency of the targeted disease gene in future generations of dogs. However, to maintain a large enough pool of good breeding stock, it may be necessary for some breeders to breed "Clear" to "Carriers" (see below)."

Clear Male Carrier Male Affected Male
Clear Female 100% Clear 50/50 Carrier/Clear 100% Carrier
Carrier Female 50/50 Carrier/Clear 25/50/25 Clr./Carr./Affctd. 50/50 Carrier/Affected
Affected Female 100% Carrier 50/50 Carrier/Affected 100% Affected
"Ideal Breeding Pair - Puppies will not have the disease gene (neither as Carrier nor as Affected)."
Breeding Is Safe - "No Affected puppies will be produced. However, some or all puppies will be Carriers. Accordingly, it is recommended that Carrier dogs which are desirable for breeding be bred with Clear dogs in the future, which will produce 50% carrier and 50% clear animals, to further reduce the disease gene frequency. These offspring should be tested for this defective gene, and if possible, only the clear animals in this generation should be used."
High Risk Breeding - Some puppies are likely to be Carriers and some puppies are likely to be Affected. Even though it is possible that there will be some clear puppies when breeding "Carrier to Carrier", in general, neither this type of breeding pair nor "Carrier to Affected" are recommended for breeding.
Breeding Not Recommended - "All puppies will be genetically and medically affected."
SOURCE: VetGen Breeding Strategies

Breeding Advice

"Our research has also demonstrated that the frequency of the PLL mutation is extremely high in the PLL-affected breeds that we have studied in depth. This means that allowing only CLEAR dogs to breed could have a devastating effect on breed diversity and substantially increase the likelihood of new inherited diseases emerging. Therefore, we strongly advise breeders to consider all their dogs for breeding, regardless of their PLL genotype. GENETICALLY AFFECTED and CARRIER dogs can be bred with, but should only be bred to DNA tested, CLEAR dogs. All puppies from any litter that has at least one CARRIER parent should be DNA tested, so that the CARRIERS can be identified and followed clinically throughout their lives. This practise should be followed for at least one or two generations, to allow the PLL mutation to be slowly eliminated from the population without severely reducing the genetic diversity of breeds at risk."
Source:Animal Health Trust

LOL... No, I didn't say this. This is "Bdreeding Advise" from Animal Health Trust. That you can find here at this link.
Thank you, KnD

Thanks to this new tool there is NO reason for a breeder to be breeding in the dark any more and thanks to OFA there is also NO reason why they can't show you their public PROOF of their testing results for any issues.

There are new tools for breeders becoming available every year/day. Why not take advantage of these helpful tools ??? We'd be fools not to. If our goals truly are to improve the breeds we love, then why wouldn't we use the tools we have now and the new ones as they become available.

If you, as a puppy buyer, see a breeder with puppies available and there is no evidence of testing on OFA or a breeder tells you they do not test or believe in testing..... RUN. If they can't show you public proof on OFA RUN!! Just becuse they say it is so.. doesn't make it so.

It is your money and your puppy, you deserve to get what you pay for. Ask about the health testing for the sire and dam and if they are on OFAthe public data base... Ask about hips, patellas, eyes, elbows and heart. PLL is the newest test, it is not the only test.

This is your new baby you are buying. You have rights and your new cuddle baby has rights.

Primary Lens Luxation (PLL) Clear Kennel

KnD has a goal. Well, we have many goals when it comes to these great little animals we call "Rat Terriers", but this goal I am talking about is a PLL clear kennel. Like I said though, it's not our only goal. We won't give up good qualities only to boast that we have all PLL clear dogs. This genetic issue can be controlled with a simple one time DNA test. If we test and breed wisely we can keep our good qualities and breed away from this issue, but we won't do it at the expense of losing good qualities. PLL can be VERY well managed and easily. I actually worry a bit when I see breeders boasting about this. It is just too early at this point and time to throw away all breeding dogs based only on this ONE manageable issue.If a breeder culls all his imperfect dogs, there will be needless sacrifices eliminating valuable assets in the genepool. As a breed, Rat Terriers are not ready to limit their diversity.