In 1996, a PBGV imported into England from France was tested and found to have
Primary Open Angled Glaucoma. This was the first known case in the
UK. It set in motion many years of intense effort and liaison between the
BGV Club, Peter Bedford Professor of Veterinary Ophthalmology and the Animal
Health Trust in researching and attempting to eradicate this eye disease from
the breed. Regular eye testing and now DNA testing play a large
part. There has been no indication of the disease in GBGVs.
WHAT IS GLAUCOMA?
PRIMARY GLAUCOMA is an inherited canine condition.
It is sub-divided into two types - Open Angle Glaucoma (POAG) and Closed
Angle Glaucoma (PCAG). In both forms glaucoma results from reduced
drainage of fluid within the eye, causing a build up of pressure
and damage to the delicate structures within the eye. This in turn
leads to pain and probable blindness.
Closed angle glaucoma This type of glaucoma is more difficult
to detect as the problem occurs further down in the eye structure and pressures
can be OK one day and escalated the next. It is more complex
than POAG and may involve more than one type of mutation making it harder to
find in the canine DNA. Although rare, during the screening process of
PBGVs, Primary Closed Angle Glaucoma has been found.
Open angle glaucoma is a disease in which the cells that produce
sight in the retina are destroyed by a slow rise in the internal fluid pressure
in the eye. Normally this fluid, known as the aqueous, is constantly produced
inside the eyes to feed the lens and the cornea. It is drained from the eye
back into blood vessels and the production and drainage rates are
balanced. In POAG it is a disturbance of drainage which leads to an
accumulation of this fluid and hence the pressure rise. The sight gradually
diminishes and, as the fluid pressure increases, the eye enlarges and the lens
may dislocate. Eventually the dog becomes blind.
The British Veterinary Association/Kennel Club Eye Scheme offers the
facility of eye testing to screen for inherited eye disease. Anyone
can use the information to eliminate or reduce the frequency of eye disease
being passed on to puppies and, importantly, it gives early warning where
treatment may be needed to delay onset.
Although any breed can be examined for eye disease, currently only the results
of those breeds that appear on a Kennel Club list (Schedule A) have
these included on the KC computer records and published in the KC Breed
Records Supplement. The eye test certificate records any possible
problems and, importantly, whether a PBGV that has been Genetically diagnosed
by DNA test as having POAG is Clinically Affected or Clinically Unaffected
at the time of eye testing. These eye test results for any PBGV
affected by POAG may change from one test to the next, depending on whether the
eye drops used are keeping the pressures under control.
Put simple this means:
CLINICALLY UNAFFECTED-EYE PRESSURES SATISFACTORY AT TIME OF EYE TESTING CLINICALLY AFFECTED-EYE PRESSURES RAISED AT TIME OF EYE
Message from Peter Bedford:
"Undoubtedly there is evidence that Open Angle Glaucoma is
inherited. This disease is difficult to manage because it is often silent in
its approach and, by the time the diagnosis is made, the dog's sight is badly
affected and the eye may be enlarged. Once the process starts it is almost
impossible to control. The earlier the diagnosis, the better the chance of
UPDATE FROM PROFESSOR PETER BEDFORD – JANUARY 2021 There is an important point to make that Eye Testing in BGVs is not just about Glaucoma, but it
creates awareness about emerging diseases. The fact that Glaucoma may be present does not
render immunity to other, say retinal or lens, problems. A case in point would be the Labrador
with 5 inherited ocular diseases. So with PBGVs we should ideally DNA test for POAG and
clinically test for other possibilities.
1. DNA test: Unless Hereditary Clear every individual PBGV should be tested once for
POAG and ideally only the "Clears" bred from.
2. Clinical examinations: Breeding stock should be examined before mating, with the
certificate being valid for 12 months. It would then be necessary to check in mid-life and
at 8 years of age to check for other emerging problems. The ideal however is to test
annually to close down the net for possible emerging problems.
Regular checking after 8 years of age would not be essential for hereditary disease but
would pick up individuals with aging changes, neoplastic disease and "other" conditions,
the examination being a simple health check. So the timescale could vary with the
owner’s enthusiasm for regular checks. I think every 2 years after age 8 is adequate, but
of course it is likely that aged individuals would be under veterinary care anyway.
EXPLAINING THE EYE TESTS
As several factors were involved, for many years the BGV
Club in collaboration with Prof Peter Bedford concentrated on abnormal
anatomy in the drainage angle and subtle pressure rises in the eye. They
therefore encouraged two types of eye testing - gonioscopy and
tonometry. Only tonometry is now needed.
(The abnormal anatomy). This is an eye examination,
separate from the routine one carried out under the BVA/KC/ISDS Eye
Scheme. It is done to detect glaucoma predisposition, or how likely the
eye is to develop glaucoma. This test only had to be done
once in a PBGV's lifetime, from 4 months old onwards. It ensured
the angle was open and provided information on what is generally described at
pectinate ligament dysplasia. For POAG the angle is not abnormal in
clinical appearance in affected dogs and the advent of DNA testing early 2015
rendered this test unnecessary.
(The pressure). This BVA/KC/ISDS regulated test,
which still takes place for PBGVs, measures pressure within the eye and
out-flow pressure. It aids early identification of problems such to POAG,
Progressive Retinal Atrophy and Lens Luxation. It is ideally done annually,
preferably up to the age of 9. Twice a year is advisable and, if a
dog is related to a known "Affected", every 3 months.
WHAT RECORDS DOES THE BGV CLUB HOLD?
From 2006, after members had sent in the results of their PBGVs' eye tests
(with their consent) the BGV Club committee compiled a full record of
all who had undergone eye testing. For a small fee to cover printing
and postage, this was made available in booklet form to club members, with
the BGV Club retaining full copyright and a restriction on reproduction.
The aim of making the information available to members was to help breeders in
their selection of sire and dam in an effort to control POAG in the breed.
In 2014-15 this method of maintaining a track on PBGV eye health was
superseded by the advent of DNA testing and the official Kennel Club
publication of results.
DNA Testing In the UK, the PBGV was originally the first breed
certified for POAG under the Eye Scheme. After many years' research, in
2014 the Animal Health Trust gave the exciting news that they had
identified the genetic mutation responsible for POAG in PBGVs. Since
early 2015 a DNA test has been available. This test largely obviates the
need for gonioscopy and will be invaluable in eradicating the disease from
PBGVs as there is no predisposing factor that can be screened for by eye
examination before the onset of the disease. Following closure of the
AHT and until the newly formed Canine Genetics section gets fully under way
again, you can send cheek swabs to Animal DNA Diagnostics, having first
paid for the test on-line or made an order by phone. Animal
DNA Diagnostics analyses these and sends a Letter of DNA
Analysis, telling you whether your PBGV is Affected, a Carrier, or Clear of the
disease. They also send results to the Kennel Club.
DNA TESTING RESULTS From early 2015 the AHT provided the BGV Club with regular
updates on how many DNA tests by country had been carried out by
them. Naturally, over time, the number decreased as most owners
had come on board already. The AHT also provided a list of
those countries from which less than 5 samples had been received.
This was probably because the breed is numerically small in some countries.
Another factor in the diminishing number of DNA tests being
carried out is that, armed with the knowledge of a PBGV's health status,
breeders can now avoid a breeding that poses a risk.
The KC also publishes results of all PBGV DNA screening passed onto them by
laboratories. However this list is incomplete. The absence of
published results on their website may be due to a number of reasons one of
which is that, at the time of testing, the puppies had not been
issued with full registration details so the DNA results could not be added to
To help breeders when planning a litter, the BGV Club therefore provides a more
complete list of DNA POAG testing results, which is updated regularly.
ANSWERING YOUR QUESTIONS ABOUT
DO ALL PBGVs NEED TESTING REGARDLESS OF AGE? YES!!!
Certainly all breeding stock should be tested. However, in the knowledge that a
Clear to a Clear mating will produce all Clear puppies, consider which PBGVs
need to be tested. If you own several you may not need to have all of
them tested as you may be spending money unnecessarily. Look at your pedigrees
and start with the older hounds. In many cases this will entail liaison between
breeders where one has used another's stud dog. If both sire and dam are tested
Clear, off-spring from that mating will automatically be *Hereditary
Clear, thus no need to test them. However, with the various possible
permutations, any other than progeny from two Clear parents will require
testing to establish their status. This is especially important with those
destined for reproduction, as the key to managing genetic conditions with a DNA
test through successive generations is in knowing exactly where the faulty
copies of the genes are.
* ............ from the KC regarding DNA testing
of Hereditary Clear Dogs. Pedigree error is a known phenomenon. DNA tests exist
to ensure that no Affected puppies are born. The Hereditary Clear Status will
therefore be limited to two Generations from January 2022,** i.e. great
grand progeny (3rd generation) will need to be tested. ** And an update from the KC dated 6 July 2021 - "Originally
scheduled to come into effect in January 2022, this has now been postponed to
2023 to allow for necessary development work to be completed and in order for
‘hereditary clear’ status to be as effective and reliable as possible".
IF A BREEDING BEWEEN TWO CLEARS BEARS NO RISK, WHAT ARE
THE CONSEQUENCES OF OTHER MATINGS?
For example, a Carrier can still be used for breeding purposes but the Carrier
will need to be put to a Clear to avoid producing Affected offspring. The
resultant litter from such a mating would produce on average 50% Carriers
of the mutation. Although statistically two Carriers will produce Affected
and Clear, this isn't guaranteed. Each dog carries one good and one faulty
gene, so there is a chance that both sire and dam passed on their good gene. As a breeder, even if you endorsed your puppies "Progeny not eligible for
registration", based on known test results of the parents, if your litter
is other than 100% clear, it will be your responsibility to contact those who
bought a puppy from you, advising they get their PBGV's DNA analysed if they
intend breeding - and making them alert to the possible consequences of
SO SHOULD WE BREED FROM CARRIERS? As part of her Animal Heath Trust work Cathryn
Mellersh produced a valuable and useful paper on the subject giving
advice that Carriers should always be included in the first one or two
generations that follow the launch of a DNA test for a recessive
This is regardless of the frequency of the mutation as it gives breeders the
opportunity to capture desirable traits, such as breed type and temperament,
before they start to select for dogs that are Clear of the mutation.
WHAT IS THE DIFFERENCE BETWEEN ORDERING A SWAB TEST
KIT AND ORDERING SWAB TESTING? When you order and pay on-line or by phone for
a DNA test, you will be sent a swab test kit and instructions how to use it. At
the time of ordering you will provide various details about your BGV including
registered name, registration number, provisional name if not already
registered, date of birth, sex and microchip number.When you have a kit
and have swabbed your BGV's mouth, you then send it off for testing
IS VETERINARY OR OTHER RESPONSIBLE CONTROL NEEDED WHEN SWABBING? Wiping round the inside of your BGV's mouth and cheeks is
not difficult therefore it is not necessary to seek help from your
vet, unless you want him/her to confirm that he/she has checked the microchip
number during swabbing.
DO I GAIN ANY BENEFIT FROM BEING AN ASSURED BREEDER? At the moment there are no discounts for Kennel Club
Assured Breeders which can be applied for purchases at Animal (DNA)
DO ANY CONDITIONS APPLY FOR AN ASSURED BREEDER? As a Kennel Club ABS member, you are obliged to DNA
test your PBGVs. This became effective from 20 July 2016. It will
not be necessary for those who breed from a Clear sire and Clear dam, as the
offspring will be automatically clear (but see * before).
THE AHT (CANINE GENETICS) ALREADY HOLDS MY PBGV'S SWABS
If a sample was used in the AHT's research and
contributed towards finding the causal mutation for POAG in PBGVs, they
would have reported their findings directly to the owner.
In the event, only a few cases were used to achieve this goal. PBGVs whose
eyes were OK were not needed. While an increase in the intra-ocular
pressures would indicate a case, an absence of this increased pressure
didn't necessarily indicate an unaffected control - the PBGV could
have been a carrier. Submissions for DNA testing to any laboratory
should ideally be traceable from when the order is placed through to providing
the result. An exception to this is where a new sample is unobtainable because
the dog has passed away since the research sample was submitted. If you
ever need information on a DNA test that was done some time ago, ask for a
Letter of DNA Analysis and give a donation to help with the cost of
HOW DO I FIND OUT THE STATUS OF A PBGV WHEN CONSIDERING A MATING OR BUYING A
PUPPY? DNA test results are gradually fed through from the
laboratory doing the test to the Kennel Club for publication. However bear
in mind that the KC list of DNA test results is by no
means exhaustive, as some information may not have been available to them
at the time, such as registration details. You can search for a PBGV
here, on the Kennel Club website Alternatively, you can also view
information on any PBGV's DNA status by using the BGV Club compiled
Test Results here. Another useful source of information
can be found on the PBGV Club of America website which gives details of
all PBGVs either registered with the AKC or shown in American PBGVs'
pedigrees. The information includes DNA test results.
WILL I STILL NEED TO GET MY BGV's EYES TESTED?
YES!!! DNA testing is not an alternative to clinical
testing but rather a tool to be utilised by breeders in conjunction with their
normal selection criteria of conformation, temperament etc. Any dog or
bitch intended for use in breeding should continue to be clinically
screened on a regular basis. Certainly an eye examination before breeding is
advisable in case there is a problem; and continued regular testing will
highlight any problem.
MOST IMPORTANTLY Even if you have obtained a DNA analysis, bear in mind that
causes of glaucoma can be genetic or acquired, such as infections or trauma
(known as secondary glaucoma). Your PBGV may be predisposed to
a combination of genetic mutation and a concurrent acquired eye
disease. In addition, with evidence that POAG can present in older
dogs, eye testing into old age on an annual basis is therefore extremely
desirable. Great strides have been made in detecting the gene
that causes the mutation leading to POAG and, while there is certainly no need
for alarm, bear in mind that this is an evolving science and there may always
be the exception that proves the rule. If a problem is found early,
there are remedies which may increase the length of time that your PBGV's
eyesight remains good.
Eye testing should still take place, as there are other eye diseases that
might be detected. Picking them up early will help prevent it becoming an
issue for the breed in the future
If you have any questions about DNA testing for POAG in PBGVs, contact
Vivien Phillips, 01442 851225, email@example.com
Within the first year of DNA testing for POAG, over 1,050 PBGVs worldwide
were tested by the Animal Health Trust.
OTHER EYE PROBLEMS
While POAG and cataracts remain the main problem in the breed, there is some
minor evidence of diseases such as Persistent Pupillary Membranes (PPMs)
and Lens Luxation.
For more details go to the Specific Concerns page.
CONTINUE TO CHECK EYES REGULARLY, IT MAY SAVE YOUR PBGV'S SIGHT!