INHERITED EYE DISORDERS & KUVASZ
by Susan Secor

It has been six years since the Kuvasz literature had something to say about heritable eye disorders. An article written by Mayling Koval (Koval, 1988) informed Kuvasz owners and breeders about the CERF eye registry. It was reported there that only 6 Kuvasz had been registered with the CERF by August 1988.

Since then, more Kuvasz have had their eyes examined and some breeders have started to pay attention to this aspect of their breeding programs. The most recent AKC Awards publication (AKC, 1994) reported eleven CERF registrations during the first quarter 1994 alone. This is encouraging, but there is much more to be done. To avoid the heartbreak experienced in other breeds where little was known about eyes, more of our dogs must be examined and examined repeatedly over their entire life spans. In the past three years (1991-1993) only 50 dogs were examined; since some breeders are already examining their dogs multiple times, the actual number of individual dogs may be even less than that. Yet in that same three year period, there were 304 AKC Kuvasz litters produced. An educated guess is that very few of those litters had parents with recent eye exams. The present state of knowledge and awareness suggests a widespread belief that ignorance is bliss. The purpose of this article is to change that.

People who care about genetic eye health include not only conscientious breeders, but also owners who hope their dogs will lead high quality lives that include good eye sight and the absence of pain. This article presents recent Kuvasz eye research data from CERF; discusses implications of these data; and provides specific recommendations about breeding and about learning more about the status of genetic eye disorders in our breed. It is written with detail that breeders need to have, yet provides information for the educated buyer who cares about the background of the dog being acquired.

TELL ME AGAIN, WHAT'S CERF?

The Canine Eye Registration Foundation (CERF), founded in 1974 by concerned owner/breeders, has the goal to eliminate heritable eye disease in purebred dogs through research, education, and maintenance of a centralized national registry. The CERF registry and research databases have been maintained at Purdue University's School of Veterinary Medicine since 1988 as a subsidiary of the massive Veterinary Medical Data Base there. To be eligible for a CERF number, a dog must have an ophthalmologic examination and be certified free of major heritable eye disease by an American College of Veterinary Ophthalmologists (ACVO) Board-certified veterinary ophthalmologist. A major disease is one that can cause pain or blindness. A number of other less severe eye conditions can exist in a dog which is CERF-cleared of major eye disease. The CERF registration is valid for twelve months; a dog must be reexamined and certified annually to maintain its registration number.

CERF, a group of nonveterinarians who maintain the registry, relies on the ACVO Genetics Committee for the technical guidelines as to what constitute genetic disorders. There are four disorders for which recommendations exist against breeding and for which CERF will not issue a number (this applies to all breeds): progressive retinal atrophy (PRA), certain cataract conditions, congenital retinal dysplasia (geographic or detached), and retinal detachment. In addition, there may be breed specific disorders that make an affected member of that breed ineligible for CERF registration. There are no such disorders for Kuvaszok at this time due to insufficient information.

THE KUVASZ DATA

It is through CERF and the process described above that data about eye problems in the Kuvasz are available. Tables 1 and 2 present information about Kuvasz whose eyes were examined during 1991 (the year in which computerized forms were instituted) through 1993. They are reported from the CERF research database, which consists of data generated by all exams performed by veterinary ophthalmologists. The database does not include identifying information about the dogs, hence the data are strictly anonymous.

Table 1 contains annual summaries of total Kuvasz examined, including number that were evaluated normal (not showing any problems); number that had one or more problems; and number of different problems that were observed.

Table 2 lists the disorders seen in the Kuvasz examined, in order of appearance on the CERF examination form. In reviewing this table, recall from Table 1 that the number of dogs examined is extremely small. It would be unwarranted to draw conclusions about such things as the presence of distichiasis or the relative absence of retinal atrophy.

Table 3 contains the definitions and breeding recommendations for the problems seen among Kuvaszok. They are based on information provided by the ACVO Genetics Committee and augmented by personal conversations with veterinary opthalmologists Dr. Todd Hammond and Dr. Denise Lindley who is also a member of the Genetics Committee and the CERF liaison. There are two categories of breeding advice (ACVO, 1992): 1) NO, for where substantial evidence exists that supports heritability of the disorder and/or the disorder represents a potential compromise of vision or other ocular function, 2) BREEDER'S OPTION, where disorder is known or suspected to be inherited but does not necessarily represent potential compromise.

Table 1. Summary Data of Kuvasz Examined 1991-1993

SUMMARY

BOTH SEXES

M

F

1991
Total examined
Total normal
Total w/ 1 or more problems
# problems in breakdown

1992
Total examined
Total normal
Total w/ 1 or more problems
# problems in breakdown

1993
Total examined
Total normal
Total w/ 1 or more problems
# problems in breakdown


10
8
2
2


10
6
4
10


30
23
7
7


6
5
1



6
4
2



15
13
2


4
3
1



4
2
2



15
10
5

Table 2. Eye Problems Seen in Kuvasz 1991-1993

EYE DISORDER

OCURRENCES
(1991-1993)

GLOBE: No disorders reported

EYELIDS:
Distichiasis

THIRD EYELID: No disorders reported

CORNEA:
Dystrophy-epithelial/stromal

UVEA: Iris colomboma
Persistent pupillary membrane

LENS: Cataract-noninherited or significance unknown
Cataract-inherited

VITREOUS: No disorders reported

FUNDUS: Retinal atrophy-generalized

NORMAL

0

4

0

1

2
6

2
3

0

1

37


WHAT DO THESE NUMBERS REALLY MEAN?

It is an unavoidable statistical reality that the sensitivity of detecting genetic disorders in a breed is greater when large numbers of dogs are examined. Furthermore, the relative lack of disorders is often only a reflection of the paucity of examinations reported (ACVO, 1992). Because so few Kuvasz have been examined and because no more than five of them are seven years or older, virtually nothing is known about eyes in the mature Kuvasz.

We can use retinal atrophy for an example of this absence of knowledge. CERF data in the late 1980s recorded incidence of progressive retinal atrophy in 79 breeds (Freer, 1988); it has also been seen in mixed breeds. We do not have data to know with certainty whether this is a problem in Kuvaszok, but it is generally believed that progressive retinal atrophy is common to nearly all breeds.

In the single Kuvasz occurrence of the disorder in 1991-1993, a seven year old dog had generalized retinal atrophy. We know nothing else about this particular dog, but that disorder typically leads to blindness. Since there is presently little evidence to suggest that Kuvasz are going blind at an early age, we might suspect that if retinal atrophy exists in the Kuvasz, it occurs later in life. In other breeds with late onset (e.g. Tervurens), it is often not identified by routine ophthalmoscopic examination until as late as eight or nine years of age. Earlier diagnosis is possible through electroretinography, which records the electrical response that follows stimulation of the retina by light. Another diagnostic tool has just recently been announced that is revolutionary because it deals directly with genotype. This blood-based DNA test to identify a certain form of PRA (rod-cone dysplasia 1) in Irish Setters unequivocally identifies genetically normal, affected, and carrier dogs. The test holds promise for all purebred dogs as research in this area continues.

In the meanwhile, for other breeds and other forms of PRA, retinal atrophy that is late in clinical onset and not diagnosed is particularly bad news where it involves breeding stock. By the time a routine exam would detect the disorder, a dog may have been bred several times. In that case, damage control is often limited; about all that can be done is to identify the original carriers and avoid breeding to their descendants.

So, again, what do the Kuvasz numbers mean? They really mean that we don't know very much about anything, and that could mean serious trouble for our beloved breed.

Table 3. Definitions and Breeding Advice

DESCRIPTION OF DISORDER 

BREEDING ADVICE 

DISTICHIASIS
Eyelashes abnormally located in the eyelid margin which may cause ocular irritation. Distichiasis may occur at any time in the life of the dog.

Although the hereditary basis has not been fully established, it is probable due to the high incidence in some breeds. Because distichiasis is felt to be a recessive trait, breeder discretion is urged and affected dogs should be bred to lines clean of the same traits in order to dilute the genetic problem. 

CORNEAL DYSTROPHY
Noninflammatory, developmental, nutritional or metabolic abnormality; dystrophy implies a possible hereditary basis and is usually bilateral.

There are some breeds in which this is a major problem, that is, is severe or blinding (e.g. Siberian Husky, Shetland Sheepdog). At this time, though, it is at the breeder's discretion for the Kuvasz.

IRIS COLOMBA
A congenital cleft or defect.

Although there are exceptions, such as the Rottweillers, in other breeds this disorder occurs only sporadically. Breeder's discretion advised.

PERSISTENT PUPILLARY MEMBRANE
Persistent blood vessel remnants in the anterior chamber of the eye which fail to regress normally inthe neonatal period. These strands may bridge from iris to iris, iris to cornea, iris to lens, or form sheets of tissue in the anterior chamber. The last 3 forms pose the greatest threat to vision and when severe, vision impairment or blindness may occur.

Usually breeder option, although there are some breeds in which the problem is so severe that affected dogs should not be bred (e.g. Chow Chow, Basenji). Certain PPM conditions can lead to further disorders such as cataracts or corneal opacity; these may result in advice that the dog not be bred. Otherwise, advice is the same as for distichiasis.

CATARACT
Lens opacity which may affect one or both eyes and may involve the lens partially or completely. In cases where cataracts are complete and affect both eyes, blindness results.

Breeding not recommended for any animal demonstrating partial or complete opacity of the lens or its capsule unless the examiner has also checked the space for significance of above cataract is unknown. The prudent approach is to assume cataracts to be hereditary except in cases known to be associated with trauma (e.g. toxic substance in eye); other causes of ocular inflammation; specific metabolic diseases (e.g. diabetes); PPMs; persistent hyaloid or nutritional deficiencies; or senile degeneration.

RETINAL ATROPHY
Progressive retinal atrophy (PRA): a degenerative disease of the retinal visual cells which progresses to blindness. This abnormality may be detected by electroretinogram before it is apparent clinically. In all breeds studied to date, PRA is recessively inherited.

Breeding is inadvisable where there is bilaterally symmetric retinal degeneration (considered to be PRA unless proven otherwise).

Table derived from information provided by ACVO, 1992; Hammond, 1994; and Lindley, 1994.


THEN WHAT SHOULD WE DO . . .?

First, be aware that having a CERF number means only that no major inherited disorder is clinically present at the time of exam; it does not rule out the possibility that the dog has a disorder that is not detectable by the routine opthalmologic exam. Also, a CERF number does not preclude the existence of other disorders of concern. Some of the information needed to make breeding decisions is contained on the owner's copy of the exam form. The other information that you'd want to have, such as, is the dog going to be affected in the future or is it a carrier of undesirable traits, might not be available.

The ACVO Genetics Committee strongly recommends annual evaluations of dogs of all breeds as the first step in control of hereditary eye disorders. This is necessary not just for popular stud dogs, but for any dog that has been bred or that is being otherwise watched closely by its owner. It is the frequency needed to detect a problem in a timely fashion, and to identify trends in eye disease and breed incidence.

There is help available to accomplish screening on a continuous basis. ACVO Board-certified veterinary ophthalmologists are highly trained and dedicated specialists who have entered a demanding profession because they care about keeping our best friends free of eye problems. Their advice is given to that end. We are fortunate that such resources are there for us, however, those ophthalmologists who do breeding exams are in the unenviable position of sometimes having to deliver bad news. To wit, animals affected with major problems should be removed from breeding programs so genes responsible for these diseases are not spread throughout the gene pool before it becomes almost impossible to find animals that are free of the traits.

These doctors are available at eye clinics sometimes held at dog shows or sponsored elsewhere by local breed clubs. While these clinics provide a welcome service, many ophthalmologists prefer examinations in their own offices where they have their support staff and other diagnostic tools available. Time is scheduled there for a thorough exam and for counseling.

There are approximately 150 veterinary ophthalmologists in the US. If you are not aware of one in your area, Susan Secor (telephone 719-495-3783) has a current ACVO list and can put you in touch with one closest to you.

Not having our dogs checked doesn't mean they don't have a problem. It must be kept in mind that no news is not necessarily better than bad news. It is only with this information -- good and bad -- that we can make intelligent, informed decisions. If widespread and frequent examination reveals that our breed is relatively free of eye disease, so much the better. If not, then we have the responsibility to save our breed from irreparable harm. The more forthcoming Kuvasz enthusiasts are about examining their dogs and exchanging information, the better off our breed will be in the future.

REFERENCES

American College of Veterinary Ophthalmologists, 1992, Ocular Disorders Proven or Suspected to Be Hereditary in Dogs, ACVO.

American Kennel Club, 1994, AKC Awards, May:CRF11.

Freer, Hilary, 1988, CERF: Better Eyes, Better Dogs, AKC Gazette, July:48-50.

Canine Eye Registration Foundation, Eliminating Heritable Eye Disease in Purebred Dogs pamphlet, undated.

Koval, Mayling, 1988, What Kuvasz Owners and Breeders Should Know about C.E.R.F., Kuvasz Club of America Newsletter, October 3.

Hammond, Todd B., DVM, DACV0, 1994, personal conversations, May.

Lindley, Denise, DVM, MS, DACVO, 1994, personal conversation, May.

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