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Advancing knowledge of eye diseases

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01 December 2008, at 12:00am

JOHN BONNER talks to one of the UK’s leading lights in veterinary ophthalmology

NO one has yet had the opportunity to study a history of British veterinary ophthalmology but when such a volume is eventually written, readers will find that it has a peculiarly lop-sided index.

The B section is likely to be disproportionately long and will be dominated by references to a single name – Barnett.

Keith Chartres Barnett, OBE, has been the leading light of this small but vital clinical specialty for almost 50 years as a staff clinician at the London and Cambridge schools and as head of the ophthalmology section at the Animal Health Trust. So he has done more than anyone else in this country to advance knowledge of the treatment and, more importantly, the prevention of eye diseases in all domestic species, but particularly in dogs.

Dr Barnett’s CV lists more than 100 books, chapters and original papers on a wide range of inherited and acquired conditions. But his influence can also be measured in terms of the number of prominent veterinary ophthalmologists who have been his students and coworkers over the years and the enduring gratitude of the clients whose animals he has successfully treated.

Born in Yorkshire, Dr Barnett had always wanted to be a vet and entered the Royal Veterinary College after completing his National Service in 1951. When he graduated five years later, he spent 18 months at a mixed practice in Kent before returning to Camden Town as a house surgeon working with Gordon Knight.

A great teacher

The then Queen’s veterinary surgeon was a huge influence on Keith’s career and sparked his interest in ophthalmic surgery. “Gordon was not an especially good lecturer but he was a great teacher for anyone lucky enough to work directly with him.

“He was a quite brilliant general surgeon and one of his special interests was eye surgery. Even then in the late 1950s he was routinely doing cataract extractions with very good results.”

Under Knight’s supervision , he stayed on to do a PhD on progressive retinal atrophy in the miniature poodle before being transferred to Cambridge in 1963 to establish an ophthalmology research unit. He went on to become assistant director of research before joining the Trust in 1975 where he was asked to set up the comparative ophthalmology unit. While he officially retired in 1996 at the age of 68, he was retained as a consultant and still works there two days a week.

Although he was looking at eye problems in horses and exotic species, the bulk of his caseload was canine disease. About 60% of those animals were known, or later found, to be suffering from inherited conditions.

Even though Dr Barnett is highly critical of the rigidly observed breed standards that have caused many of those problems, he is reluctant to point the finger of blame at the Kennel Club. Indeed, he found the recent BBC documentary which claimed that “pedigree breeds are falling apart at an alarming rate” to be both unfair and sensationalist.

Dr Barnett is a member of the Kennel Club and has received considerable financial and practical support in investigating genetic diseases. Individual breed societies have also provided tremendous help, although the problems in some breeds are seemingly overwhelming.

“If you asked me which group of people are the best to work with, I would say Cavalier King Charles Spaniel breeders. That breed did have two different forms of hereditary cataracts that have now almost completely disappeared and an incidence of retinal dysplasia that has gone down enormously.

Unfortunately, there is still that very painful condition syringomelia and a heart condition that cause many animals to drop dead in middle age. So while the people involved are wonderful, they have a breed that is something of a disaster.”

Fortunately, not all these problems are as great as those facing the poor CKC spaniel breeders. Even before Dr Barnett joined the Trust, its scientists had enjoyed success in confirming progressive retinal atrophy in red setters as an inherited condition. And by careful examination of the breeding records they were able to identify the affected lines.

With new technologies, Dr Barnett and his colleagues are now able to locate the specific gene responsible and offer tests for breeders of dogs in breeds with many inherited eye conditions such as the different PRAs found in dachshunds, setters and springer spaniels and for hereditary cataracts in staffies, Australian sheepdogs and French bulldogs.

Dr Barnett is excited by the potential for much more rapid identification of the genes responsible for inherited conditions following the completion of a project to map the canine genome. He believes that collaborations between clinicians and researchers like Cathryn Mellersh, head of the canine genetics group at the Trust, will be crucial in identifying and eliminating the causes of many such diseases.

Canine eye diseases are a particularly useful model for this sort of collaboration as they are normally single gene disorders. This means that they are not only preventable through developing genetic tests, they may also be treatable.

Of course, gene therapy has yet to fulfil its undoubted promise in treating human disease, but it was used successfully seven years ago by an American team to treat a form of retinal degeneration in briards.

Potential

Human ophthalmologists recognised the potential value of companion animal models in helping to understand human conditions. Inherited eye conditions are fairly rare in cats but a single case in a male Abyssinian cat has provided enough material for four PhDs, Dr Barnett notes. As the cat’s condition had intriguing similarities to a human form of PRA, that case was the factor which triggered a research collaboration with staff at the Moorfields Eye Hospital in London that continues to this day.

Yet despite these advances in the science underpinning veterinary ophthalmology, Dr Barnett is very concerned about the future of his clinical discipline. He is dismayed by the Royal College’s decision to end the system of certificate and diploma training.

Although he has no problems with the European College diploma replacing the national qualification, he thinks the modular certificate is a mistake which will have particularly damaging effects on the training of future ophthalmologists by lowering standards.

“I understand that there will be scope under the modular certificate system to study 76 different subjects! How can there be that many? It’s just ridiculous.”

Even more worrying, as far as Dr Barnett is concerned, is the fact that there are no longer any holders of ophthalmology diplomas still working within the UK veterinary schools.

All have retired, gone abroad or are working in private referral practices. Undergraduate training in this subject is being provided by visiting lecturers from private practice. But he says this will give neither the depth nor the continuity of training needed for young veterinary surgeons wishing to specialise in this subject.

Dr Barnett is also baffled by the RCVS’s position over who is entitled to act as examiners in assessing applicants for the ophthalmology part of the modular certificate.

The ophthalmology board insists that these examiners must be diplomates and will refuse to recognise any exam assessed by a certificate holder. But the RCVS will not allow diploma holders in private practice to take over the role.

So in the current situation, it will not be possible for any new certificates to be awarded in veterinary ophthalmology in this country. “That’s not progress – we are starting to go backwards,” he warns.