Glaucoma in the Flat-Coated Retriever

Since the Flat-Coated Retriever is an international breed, the Sharon Myers committee felt it was important to reprint these articles on a very serious health problem in Flat-Coated Retrievers that seems to be emerging in the UK. As all of our dogs come from the same original stock, we offer the following Introduction by James Wood and three reprinted articles for your consideration and would like to encourage breeders to do gonioscopy eye evaluations on breeding stock.

GLAUCOMA IN THE FLAT COATED RETRIEVER
J.L.N.Wood BSc BVetMed MSc PhD MRCVS
Head, Epidemiology Unit, Animal Health Trust, Newmarket, UK

Glaucoma is defined as an increase in intraocular pressure - the pressure within the eyeball is raised above the normal limit. Glaucoma is a painful condition, sometimes extremely so, and, to date, there is no completely satisfactory treatment, either medical or surgical. Unfortunately, therefore, glaucoma often results in total blindness sometimes necessitating removal of a swollen eye. Glaucoma, usually termed primary glaucoma, is often inherited and affects several breeds of dog, including the Flat Coated Retriever, as well as man. In cases of hereditary primary glaucoma one eye is usually affected first but the second eye frequently becomes involved later resulting in total blindness for the dog. The Flat Coated retriever is usually affected when 5 or 6 years old, although other breeds may be affected at a younger age.

Glaucoma in the dog is almost invariably due to a failure of the normal drainage mechanism of the aqueous fluid in the eye due to a number of causes. In hereditary primary glaucoma the obstruction to drainage is due to a failure in the development of the pectinate ligament through which the aqueous fluid should drain from the anterior chamber of the eye. This developmental failure is known as "pectinate ligament dysplasia", sometimes shortened to PLD, or as "goniodysgenesis". It is this abnormality that can be detected, before the pressure rises, through the examination of the eye by gonioscopy (a special type of contact lens which enables the filtration angle to be seen).

Some other breeds known to be affected with PLD, in addition to the Flat Coated Retriever, are the Great Dane, Welsh Springer Spaniel, English Springer Spaniel, Basset Hound, Cocker Spaniel, American Cocker Spaniel and Siberian Husky. The Flat Coated Retriever is a breed in glaucoma has been recognised for some time and two of our studies in the UK population which took place earlier in the 1990's have estimated the frequency of the disease to be around 1 case per 100 dogs.

Detailed studies have been carried out of the disease in the UK population of flatcoats, involving diplomate clinicians, as well as epidemiologists and statisticians. These studies have now been published in the scientific journal Veterinary Ophthalmology (Vol 1, pp85-90, 91-99). These studies have enabled several important facts about the disease in flatcoats to be properly established.

The data demonstrated a close relationship between the degree of goniodysgenesis (or PLD) and the likelihood of an animal developing glaucoma. Animals that are only very slightly affected (or are clear) are unlikely to get glaucoma and as the proportion of the eye that is affected increases, then so does the risk.

Overall, there was no indication of a substantial worsening of the condition with age and so an animal, which is screened clear at a young age, is unlikely to develop the disease later in life. Thus, animals can be screened as young adults and the likelihood of them developing glaucoma can be accurately assessed (as well as their suitability for breeding, see below).

The degree of goniodysgenesis (or PLD) was highly heritable (h2>0.7), indicating that if one bred from animals with no, or only very limited goniodysgenesis, then the offspring would be most unlikely to suffer from glaucoma. Although glaucoma itself was not shown to be inherited, the close association between the predisposing condition (goniodysgenesis) and the disease and the high heritability of goniodysgenesis can be taken to indicate that glaucoma is inherited. This is the first time that the heritability of this disease has been demonstrated scientifically in dogs.

There is now a formal screening programme for goniodysgenesis in flatcoats in the UK and whilst the scheme has not been without its critics, it is encouraging that there already seem fewer reports of affected dogs than there were five years ago.

This is a most unpleasant disease that can be inherited in Flat Coated Retrievers. However, we do now have the tools to ensure that we no longer breed affected dogs.
Funding for these studies came from The Kennel Club Charitable Trust.

Article 1: Glaucoma in Flatcoated Retrievers

This article is reprinted with permission from the UK Flatcoated Retriever Society Health Committee report. Originally printed in Autumn 1996.

As laymen we have tried to put together for you, information on Glaucoma in our breed. As breeders and owners, we realise the difficulty we "ALL" are having, to understand the development, progress, and the way to deal with this disease within our lovely breed.

At this time the incidence of Glaucoma are probably considerably higher in some other breeds, but in the Flatcoated Retrievers, it is the first time that the hereditarability of this disease has been formally shown.

In the summer of 1993, we as a breed Society were contacted by the Eye Specialist on the British Veterinary Association/ Kennel Club / International Sheepdog Society Eye Scheme Panel. As in the year or so before, several panelist had seen the occasional Flatcoated Retriever with Glaucoma. This condition is known to be inherited, serious, painful condition of the eye, the Panel took the decision to put Flatcoated Retrievers on the list in January 1994 of "Diseases under Investigation".

You will remember that the society gave you the information available in the autumn's 'health information booklet'.
Many of you will have supported Mr. Tony Reed BVSc(Hons) Cert V Ophthalmology MRCVS, who, with others in this field, and with the support of 'The Kennel Club Charitable Trust', studied 'Canine Glaucoma', Flatcoated Retrievers being part of the study.

As you know, Tony Reed at the time developed his own private scoring system, this enabled him to assess each individual dog, the statistical data collected was then analysed, this showed the connection between PLD(pectinate ligament dysplasia) and glaucoma in Flatcoated Retrievers.

"Pectinate ligament dysplasia(PLD) in dogs is a congenital ocular abnormality affecting the iridocorneal angle, the presence of which may lead to adult-onset primary glaucoma". We are so sorry that there is no other way to explain it but in technical terms, there are very few of us within the breed that find Glaucoma or the reason Flatcoats have Glaucoma easy to understand.

We understand that from the abnormality observed by gonioscopy in Flatcoats 'PLD' is considered to be the most suitable term. PLD refers to malformation of the pectinate ligaments, ranging from mild localised thickening and/or shortening (resulting in loss of "interligament spaces" in a small region of the overall irridocorneal(drainage) angle's circumference) to extensive thickening and/or shortening of ligaments (to the point where part of all of the ICA circumference appears as a sheet of poorly differentiated inesenchymal tissue). If you follow this to its conclusion this is why Tony Reed had to have a scoring system "the mild being 2/3 the extensive thickening 4/5" as part of this research study.

In laymen terms if you think of 'normal' as a well risen even sponge cake, with the air bubbles one below the other making a free drainage area. Grade 2 & 3 starting at one side of your cake, where the draft has caught it and it had gone solid as in a cake but a high percentage is still the perfect sponge. Grade 4 & 5+ gradually become more cake like, until there is more cake than air holes. We are told that possibly, grade 1,2, & 3 possibly never get Glaucoma, but grade 4 & 5+ have a strong tendency to Glaucoma especially if there is an injury or an infection.

The message from the panel is that in January 1997, Flatcoated Retrievers will go on to Schedule 1 - INHERITED OCULAR DISEASE.

"The list of inherited eye conditions in the breeds specified are those which will be designated as "Unaffected" or "Affected" on the bottom part of the certificate and the results will be sent to the Kennel Club for publication".

There will be NO grading system as the grading of the dogs eye, was the degree the eye was affected!

For many years we have 'All' had our Flatcoats tested for PRA and Cataract, with pass certificates; we now face an uncertain future, it is a worry for us all, until several generations of our dogs are tested and more is known. This test needs only to be done once in a dog's life, it can be done from a few months of age, although we are not certain yet, at what age the Certificate will be granted.

One point has to be made; for the first few years, until there is a greater knowledge of the inheritability of this disease, we will be uncertain 'even' with clear certificates, if our stock will produce clear stock. It is possibly very important that this should be in writing; understood, and signed by the puppy buyer plus yourself when you give them both parents clear certificate, it might be wise to keep a signed copy.

Breeding from affected stock: This is a difficult one for anyone but the Eye Specialist that has tested your dogs eyes to advise you on. Do remember that after January 1997 the breed will be registered by the Kennel Club with Glaucoma and Dysplacia as "Heritable diseases", this will make breeders legally liable.

In all Flatcoats it would be wise to have a glaucoma test done early or at least at the same time as the first eye test. It is important to know the status of your dogs eyes even if it is a family dog. Then if you and your Veterinary Surgeon are aware that there is a possibility of Glaucoma, all 'Eye infections or Injuries' are treated seriously and NOT left to see if it clears up!!

Going back to our sponge cake, we can better understand why the poor drainage causes the internal fluid pressure of the eye to rise above normal and destroy the optic nerve (and hence sight).

The eye specialists tell us:
"It can present itself as an acute onset, painful and blinding condition, or as an insidious, non-painful, slowly blinding problem. Prompt Emergency treatment to reduce the fluid pressure is essential if the blindness is to be reversed, and it can, providing that the fluid pressure is brought to within normal limits within hours of the pressure rise occurring. So a sudden painful eye which may appear milky(the cornea) and red(the conjunctive/scleara) mean a Glaucoma attack.

Specialist Veterinary attention must be found immediately, otherwise the damage to the optic nerve becomes irreversible. This kind of glaucoma is bilateral, but there may be a delay of hours to months before the second eye becomes involved. Further treatment is difficult, but is developing all the time. We will keep you up to date as specialist knowledge develops.

Please for your Flatcoats sake do the best for your dogs. Glaucoma is at this time 'hopefully' a small (but painful and possibly fatal) problem within our breed. Please help keep the incidence down for the sake of our special dogs. We hope to have "Health Workshops" next year which will include well known Specialists on Glaucoma.

Article 2: Glaucoma in the Flat-Coated Retriever
James Wood, Keith Barnet and Ken Lakhani, Animal Health Trust

This article is reprinted with permission from the UK Flatcoated Retriever Society Health Committee report. Originally printed in Summer 1997.

Glaucoma is defined as an increase in the intraocular pressure - the pressure within the eyeball is raised above the normal limit. Glaucoma is a painful condition, sometimes extremely so, and to date, there is no completely satisfactory treatment, either medical or surgical. Unfortunately, therefore, glaucoma often results in total blindness sometimes necessitating removal of a swollen eye. Glaucoma,. usually termed primary glaucoma, is often inherited and affects several breeds of dog, included the Flat-coated retriever, as well as man. In cases of hereditary primary glaucoma one eye is usually affected but the second eye frequently becomes involved later resulting in total blindness for the dog.

Glaucoma in the dog is almost invariably due to a failure of the normal drainage mechanism of the aqueous fluid in the eye due to a number of causes. In hereditary primary glaucoma the obstruction to drainage is due to a failure in the development of the pectinate ligament through which the aqueous fluid should drain from the anterior chamber of the eye. This developmental failure is known as "pectinate ligament dysplasia", sometimes shortened to PLD. It is this abnormality that can be detected, before the pressure rises, through the examination of the eye by gonioscopy (a special type of contact lens which enables the filtration angle to be seen).

Some other breeds known to be affected with PLD, in addition to the Flat-Coated Retriever, are the Great Dane, Welsh Springer Spaniel, English Springer Spaniel, Basset Hound, Cocker Spaniel, American Cocker Spaniel, and Siberian Husky.

The Flat-Coated Retriever is a breed which has been suspected of glaucoma for some time and is on the list of breeds under investigation by the RVA/KC/ISDS eye diseases screening programme. Statistical analysis of data collected by Tony Reed, an Ophthalmologist working at the Animal Health Trust, has shed new light on the condition in the Flat-Coated Retriever and this study has demonstrated for the first time that:

  1. The degree of PLD in an individual animal is closely associated with the likelihood of it developing glaucoma.
  2. The incidence of glaucoma in Flat-coated Retrievers (FCR) is around .97% or 1 case per 100 dogs. Although this is low, PLD is significantly more common in the FCR than in a random selection of dogs from other breeds.
  3. PLD is inherited in the FCR and has a high degree on inheritability. It is possible to predict the probability of a dog developing glaucoma from a knowledge of its parents' PLD scores. This is important because it means that a breeding programme based on breeding animals with low PLD scores is likely to be highly effective in eliminating the condition from the breed.
  4. All FCR's should be tested gonioscopically before being bred.

Further information on this research is available from James Wood or on clinical aspects of glaucoma from Jane Sansom, Animal Health Trust, PO Box 5, Newmarket, SUFFOLK CB8 7DW.

Article 3: Glaucoma in Flatcoated Retrievers

This article is reprinted with permission from the UK Flatcoated Retriever Society Health Committee report. Originally printed in 1999.

It has been 6 years since Glaucoma was first brought to our notice, within the breed. So many new people have come into Flatcoats. We the Health committee thought it would be a good time to recap.

In the summer of 1993 Professor Peter Bedford contacted the Breed Health Monitor, as, over the period of a year or so several panellists had saw the occasional Flatcoat with Glaucoma.

Mr Tony Read BVSc (Hons) Cert V Ophthalmology MRCVS Schering-Plough Resident in Veterinary Opthalmology was at that time taking an interest in the problem of Glaucoma in dogs. He offered to include Flatcoated retrievers in his study. This resulted in the "Canine Epidemiology Project" supported by the "Kennel Club Charitable Trust". The resulting paper was the "Gonioscopic findings, Prevalence and Heritability of "Pectinate Ligament Dysplasia" in Flat Coated Retrievers and it's Relationship with Glaucoma". Published by J.L.N.Wood, K.H.Lakhani and R.A.Read.

This study carried out over a period of three years, included 389 Flatcoats who were examined gonioscopically and their degree of PLD assessed. It was found the prevalence of PLD was significantly higher in Flatcoats compared with the in 100 dogs from "other breeds". There was a significant association between PLD and glaucoma. The opinion was that the prevalence of glaucoma in Flatcoats is around 14 per 1000[1.4%]

A significant and positive correlation was demonstrated between the degree of PLD and the likelihood of glaucoma in Flatcoats and in their dams and sires. The analyses , based on 32 pairs of parents with a total of 70 offspring's, showed that PLD in Flatcoats is inherited.

Mr Read had his own scoring system which was mainly to help him assess individuals more objectively. A problem arose when this system was carried over into the public eye testing for Glaucoma when individual panellist opinions came into the equation. This system of scoring has now in 1999 been drooped

In 1993 We had written to Professor Bedford on behalf of the Flatcoated Retriever Society and breeders, asking the question.
"What is Glaucoma and how does it affect our dogs"?

His answer was. "Primary glaucoma is an inherited condition in which the internal fluid pressure of the eye rises above normal and destroys the optic nerve (and hence sight). It can present as an acute onset, painful and immediately blinding condition, or as an insidious, non painful, slowly blinding problem. It is the former which occurs in young to middle-aged Flatcoated Retrievers.

Emergency treatment to reduce the fluid pressure is essential if the blindness is to be reversed, and it can, providing that fluid pressure is brought to within normal limits within hours of the pressure rise occurring. So, a suddenly painful eye which may appear milky (the cornea)and red (the conjunctiva/ sclera) means a glaucoma attack. Veterinary attention must be found immediately otherwise the damage to the optic nerve becomes irreversible. This kind of glaucoma is bilateral, but there may be a delay of hours to months before the second eye becomes involved.

Treatment is extremely difficult. One can either destroy by laser or cold (freezing) that part of the eye which makes the fluid , but here at the College we "bypass" the blocked fluid drainage pathway by using a tube shunt to carry fluid from the front chamber of the eye out into the tissues of the orbit.

Dogs which develop this kind of primary glaucoma- its called angle closure glaucoma - are born with an anatomical predisposition called goniodysgenesis. That part of the eye which deals with the drainage of the fluid which fills the eye is abnormal. It is called the drainage angle and a simple test called gonioscopy will dictate whether a dog has an abnormal or normal drainage angle. The test can be done in most breeds from about 4 to 6 months of age. It is only one test and the result is good for life. It is the only way of deciding which dogs will be affected in middle-age or will remain clear for the rest of their lives. If a dog has the predisposition it may develop glaucoma. Not all predisposed dogs go on to develop glaucoma, but glaucoma of this kind will not occur unless goniodysgenesis is present.

Gonioscopy is a separate examination from the basic eye examination conducted on the scheme. It is readily available but your owner must specify that they want gonioscopy or a glaucoma examination in addition to, or instead of the basic eye examination. There is a separate fee which is the same as that for the basic examination.

We asked about breeding . Unfortunately we do not know the mechanism of inheritance. Although now we do know that predisposition to this disease is inherited. The predisposition is not all or none, but is progressive and can be measured [as demonstrated in the Animal Health Trust study. The mode is in fact likely to be complex, involving several genes [similar to an attribute that can be measured on a scale like height]. The analyses importantly demonstrated a high degree of heritability, which indicate that, with the correct scheme, eradication of this highly unpleasant condition should be possible within a short time period. This situation is quite different to other complex genetic diseases such as deafness in Dalmatians, where the degree of heritability is low and so eradication , if possible at all, would only occur after many generations.
Professor Bedford's advise at that time was: In general to contain the problem, would be DO NOT BREED from the affected dog, its parents, its siblings or its offspring. Testing CLEAR does not necessarily mean that the hereditary genetic abnormality is not carried by that dog or bitch.

The collecting of, pedigree data around the affected dogs is being done from the published list in the Breed Supplement. This will be helpful in working out the mechanism of inheritance. The data is being passes on to James Wood at the Animal Health Trust..

We hope articles over the last 6 years have gone part way to helping you, the breeders and owners, to understand this painful and distressing problem
These were:
The 1993 F/C Rt Soc Health Monitor "Glaucoma 1993"
The F/C Rt Soc Health Committee Report "Glaucoma" 96
The F/C Rt Soc Heath Committee Report "Glaucoma" 97

Our prime concern must be for our Flatcoats. The advice is. "Please" Have every Flatcoat tested FOR THE DOG ALONE SAKE! It is SO important we all know the criteria of each of our beloved dogs. Then IF! Unfortunately your symptom-less dog has a "Strong Predisposition to "glaucoma". "Please" do not wait around to see if his or her eye infection or inflammation clears up, if you suspect a problem, go straight away to your Vet. TREAT IT AS AN EMERGENCY. This will help greatly with the treatment and save your dog much distress.

Over the last few years we "are" aware there have been dogs and bitches that have lost the sight in BOTH eyes. These dogs probably went through severe pain and discomfort. It must feel as if the eye is exploding in his or her head.!

If you are one of the unfortunate owners of a dog with glaucoma, please tell the breeder of your Flatcoat. If it is a Stud dog or brood bitch, please inform the breeders who have used your dog or the puppy owners from your bitch.

There is support for you especially from your "HEALTH COMMITTEE" We are increasingly aware as the number of tested dogs reaches 1000 that sadly very few of our breeding lines in the UK are safe from the predisposition to this disease even though still the number of Glaucoma cases are few. We have approximately 14 cases reported to the Health Committee [spring 99].

Because of these professional findings, the Flatcoated Retrievers was put on the list of "Diseases under investigation" in January 1994. With the evidence of inheritability the Joint KENNEL CLUB/ BVA EYE Scheme Examiners made the decision that the FLATCOATED RETRIEVER should go on to the." Inherited eye condition present within the breed [Congenital]" on January 1st 1997.

We do understand the reluctance of some owners to commit their dogs to be tested. Because they feel possibly that all testing in not uniform in its results.

This simplistic example might help you understand the problem.
Think of the covering of the eye as a sponge cake.
The perfect eye is easy to understand a perfect sponge!!
The moderately to badly affected eye is the sponge that has caught the draft, and has become cake like.

Now we come to the more difficult case the slightly affected eye!! With one spot in the corner of one quarter affected, like the spot in the cake that has not been mixed well.
Now add to this, the imaginary sponge cake is covering the eyeball of the dog!!
Imagine the other disadvantages, the construction of a Flatcoats head gets in the way of examining the eye ball.
Plus the depth of the eye socket of some Flatcoats .
Add to this trying to put and keep a contact lens on the eye of a very wiggle dog .
The great disadvantage of having the average Flatcoats tongue slurping your ear!!
The eye specialists admit it is the most difficult examination to perform.
In addition you have slight differing interpretation. This is hopefully being addressed by the "Eye Panel". Remember we have learnt a lot over these last 6 years. Methods and information are improving all the time.

At this point we should remind ALL breeders, that now the predisposition to Pectinate Ligament Dysplasia with its significant association between PLD and Glaucoma is proven, documented and published. As with Hip Dysplasia. [Both have been proven and recorded as, hereditary in Flatcoated Retrievers] To breed from untested stock makes breeders legally liable.

We as a committee can understand how frustrating the slow progress over the last few years have been.. Please remember a great deal of work has been done on both sides. We have talked and put the breeders point of view to individual "Eye panellist", who have given a lot to their time to listen patiently to us. We as a committee are concerned, that you the members, discuss this problem between yourselves and often only negative opinions come back to us third hand. We would appreciate more of you're input, please.

Many letters have been written to the B.V.A & Kennel Club, this a slow often frustrating progress. We have to remember that all the other breeds with eye problems have to be dealt with as well. Ideas have put forward, they are taken into consideration. If and when the Eye Panellist makes decisions, then the legal implications also have to be gone into. This all takes longer than we had hoped.

We need your input we need your support. We are working for you and your dogs.