PRIMARY LENS LUXATION
The lens of the eye is situated behind the iris, the coloured part of the eye. In the condition of luxation (dislocation), the lens breaks away from its retaining attachments within the eye and becomes free. In most cases, the lens passes forward and comes to rest between the cornea and the iris, in the anterior chamber of the eye. In just a few cases, the lens will pass into the posterior part of the eye or will float from one area to the other.
The term subluxation is used to denote a lens that has partially, but not completely, broken away from its attachments.
Luxation of the lens can be primary or secondary. Secondary cases are those produced by some other problem within the eye, such as cataract or glaucoma. Primary luxation is inherited and is not associated with any other eye problems but results from in-born defects in the structures holding the lens in its normal position within the eye. Glaucoma will result from a lens that is displaced into the front part of the eye if the condition is not treated surgically.
Inherited primary lens luxation occurs in several terrier breeds - the Fox Terrier (Smooth), the Fox Terrier (Wire), the Sealyham Terrier, the Jack Russell Terrier and the Tibetan Terrier. It also occurs in the Border Collie and the Miniature Bull Terrier.
Either sex may be affected and most cases occur in middle age -3 to 7 years -although there are exceptions to this rule. In a few cases, both eyes are affected at the same time, but it is more usual for there to be an interval of weeks or months, and sometimes even years, between one eye and the other. However, the condition will invariably affect both eyes in due course.
If a lens luxates into a forward position it will cause an opacity of the central part of the cornea and will lead to an increase of pressure within the eye -glaucoma -which will cause clouding of the cornea, congestion and pain, ultimately leading to enlargement of the eyeball and total blindness.
It is important to recognize the early signs of luxation, for treatment is required urgently in most cases. The signs of subluxation would not be appreciated by the owner, but can be detected by a veterinarian specializing in ophthalmology weeks or even months before actual dislocation of the lens occurs.
The change from subluxation to luxation can often be dramatic and, once the lens has passed forwards, there may be signs of irritation and discomfort and the eye may have an unusual glossy or bluish appearance. If both eyes are affected simultaneously, visual disturbances will be apparent.
In a susceptible breed it is important to consider any eye problem as a potential luxation or subluxation. What might appear to be a simple conjunctivitis may well prove to be early movement of the lens. Any apparent eye inflammation or discomfort should be checked by a veterinary surgeon and, if there is any doubt, referred to a veterinary ophthalmologist. This is especially important if one eye has already been affected by, or lost through, luxation.
When a lens has moved forwards, thus likely to result in glaucoma and loss of the eye, removal of the lens from the eye is the only possible treatment. If successful, such an operation will result in the dog having useful guidance vision. Unfortunately, although the success rate of such an operation is reasonable in most terriers, the Miniature Bull Terrier shows particular problems with this type of surgery, due to the narrow eyelid opening and the small, deep-set eye.
Where a lens has passed backwards -an unusual occurrence in the M.B.T. -treatment with drugs may well be preferable to surgery.
Primary lens luxation in the affected breeds is inherited. Studies in the Tibetan Terrier show that this is a simple recessive inheritance, (Both parents carry a normal gene, and a faulty, recessive, gene . The parents, although carriers, are unaffected by the faulty gene. Their offspring are affected, not affected, or carriers, or a mixture of these) and the same is likely to apply to all affected breeds. Those animals carrying the factor will either be carriers or will become afflicted sooner or later.
It is sometimes suggested that a blow to the eye might be responsible for dislocation of the lens. This is very unlikely, but injury might well hasten the onset in a susceptible animal. Again, glaucoma can result in luxation but, in the affected breeds, it would be far more likely that luxation resulted in glaucoma.
Under no circumstances should an affected animal be used for breeding, nor should the parents or progeny or littermates, which are likely to be carriers, be used in any future breeding program.
Control of the problem lies in the hands of owners and the Club, so that the identity of affected animals is known. It is essential to make this information available so that breeding from affected stock, or those likely to be carriers, can be avoided
BVA_eye_panelists.pdf
THE PICTURES BELOW ARRE FROM ECHOCARDIOGRAPHIC EXAMINATIONS OF TWO MINIATURE BULL TERRIERS,ONE NORMAL,AND ONE WITH SEVERE AORTIC STENOSIS BUT NO SYMPTOMS
NORMAL AORTIC VALVE VALVULAR AORTIC STENOSIS
AND%20ATRIUM%20(LA)ARE%20ROUNDED%20AND%20ENLARGED.PNG "MITRAL VALVULAR STENOSIS;VALVE IS THICKNED AND UNABLE TO OPEN.THE LEFT VENTRICLE (LV)AND ATRIUM (LA)ARE ROUNDED AND ENLARGED")
PATELLA LUXATION
The patella, or knee cap, is located in the centre of the knee joint. The term "luxating" means out of place or dislocated. A luxating patella is a knee cap that moves out of its normal location.
The muscles of the thigh is attach directly or indirectly to the top of the knee cap. A ligament, called the patellar ligament runs from the bottom of the knee cap to a point on the tibia (shin bone) just below the knee joint. When the thigh muscles contract the force is sent through the patella and through the patellar ligament and results in straightening of the knee joint. The patella stays in the centre of the leg because the point of attachment of the patellar ligament is on the midline and because the patella slides in a groove on the lower end of the femur (the thigh bone).
The patella luxates because the point of attachment of the patellar ligament is not on the midline of the tibia. As the thigh muscles contract, the force is pulled against the groove on the inner side of the femur. After several months or years of this abnormal movement, the inner side of the groove wears down and the patella is free to move out of the groove or dislocate. When this occurs, the dog has difficulty bearing weight on the leg. It may learn how to kick the leg and snap the patella back into its normal location. However, because the side of the groove is gone, it dislocates again easily.
Since the joint surfaces are bathed in a slippery joint fluid, there is usually little or no discomfort early in the process. This can cause the knee to be susceptible to other injuries, especially torn cruciate ligaments which are very very painful to the dog . And as they get older the knee can become arthritic and painful. The bones may actually curve in response to the abnormal location of the kneecap thus leading to badly shaped legs and your bully not being able to stand square...
Surgery should be performed if your dog has a persistent lameness or if other knee injuries occur secondary to the luxation. The cost is quite high for knee operations and can be a very long and painful recovery, as to what kind of surgery is best you will be best discussed with your Veterinary surgery. but a simple check up at the vets from your stud dog/broodbitch perhaps whilst they have their annul boosters could rule this problem out as it is inherited so a dog showing signs of Patella Luxation should not be used in a breeding program
If the surgery is performed before arthritis occurs, the prognosis is excellent. Your dog should regain full use of its leg. However, if arthritis has already occurred, the joint will still be somewhat painful, especially in cold weather
DNA PROFILING IDENTIFICATION
The DNA profile is the ultimate in individual identification and offers a 'tamper-proof' means of identity. The profile need only be produced once and the DNA sample used to produce it can be stored as a permanent DNA record throughout the dog's life. Identification could be essential in a number of instances. For example, the availability of a profile could be used to identify an animal that may have been lost or stolen, and subsequently recovered. The profile could also be used to check the authenticity of a DNA sample being used to screen for the presence of disease-causing genes. Many such tests are being developed and it would be invaluable to be able to verify that the correct dog's DNA is being tested for the presence of the deleterious gene. Repeating the DNA profile on the same sample of DNA being used to carry out the gene test would be straightforward and prove conclusively that the correct animal is being tested.
Please note: DNA profiles are not instantaneous, so it is worthwhile microchipping your dog in addition. They also do not give information on the disease status.
Parentage/pedigree analysis
Provided that the DNA profiles of both parents are available, pups in a litter can be profiled and their profiles checked with their parents' profile to verify that the correct parents have been registered.
DNA profiling kit request - KC DNA profiling service
DNA profiling costs £25 per dog, and this amount is payable on ordering a profiling kit. Once ordered, a kit will be sent to you together with instructions on how to get a sample from your dog (by rubbing loose cheek cells onto a swab). Once you have taken the sample, you will need to return the kit, in the envelope provided, to the laboratory. Once a DNA profile has successfully been completed, you will receive a DNA Profiling Certificate and your dog's KC records will be updated accordingly.
THE PROOF OF THE PUPPY IS IN ITS PROFILE
A more detailed explanation of the process of DNA profiling - by Dr Jeff Sampson.
Buried within the DNA of each and every individual is a special DNA signature that can be used to uniquely identify that individual. DNA profiling is the name given to the technique that has been developed to reveal this DNA signature. Initially, DNA-based approaches to identifying individuals were pioneered in humans, but the same technology has easily been transposed to the dog. Nowadays, special sequences found in DNA called microsatellites are used to build up this DNA signature. Microsatellites have become the system of choice for DNA profiling and genetic testing in humans. The US Armed Forces, FBI, Scotland Yard, The Royal Canadian Mounted Police and multiple forensic laboratories use microsatellites for their forensic, paternity and individual identification tests. The reasons that have made them come to the fore in humans are the very reasons that currently make them the system of choice for dogs.
The technique essentially involves preparing a DNA sample from an individual dog. For this we need to obtain some tissue from the dog in order to prepare the DNA. The ideal source of material would be a blood sample which will permit us to isolate DNA from the white cells; this however requires a vet to take the sample of blood before passing it onto the laboratory for testing. Less invasive techniques which don't require veterinary intervention have therefore been sought to make the procedure more convenient. One alternative source of tissue are the cells that can be easily removed from the inside of a dog's cheek, called buccal cells.
In this case all that is required is to gently rub a small plastic brush against the inside of the cheek to remove the buccal cells. The brush, containing the cells can then be returned to the laboratory for analysis. DNA can be made from both tissue sources, although considerably less DNA is provided by the buccal cells because they are considerably fewer in number.
Once isolated, the DNA can then be treated to reveal the individual-specific DNA signature. Several laboratories throughout the world have been using this technique successfully for a number of years. Many of you will have read in the dog press of the American Kennel Club's pilot study on DNA profiling which has recently been concluded.
What can DNA profiling offer? Well, as I have explained, the DNA signature that is revealed can uniquely identify an individual dog. However, the profile is not just a means of identification because it also carries within it information on the parents of the dog. This is because a puppy inherits half of its DNA from its mother and the remaining half from its father. This essentially means that half of the components that make up the profile are maternal in origin and the other half paternal. So it is in these two areas that profiling has impact: individual identification and parentage verification
