"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 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."
SOURCE OFA HERE
Dogs that have been determined as carriers and normal can be bred safely:
Autosomal Recessive Diseases
|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."|
"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
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