CAER (aka CERF)
Companion Animal Eye Registry (CAER) OVERVIEW
The purpose of the OFA Companion Animal Eye Registry (CAER) is to provide breeders with information regarding canine eye diseases so that they may make informed breeding decisions in an effort to produce healthier dogs. CAER certifications will be performed by board certified (ACVO) veterinary ophthalmologists. Regardless of whether owners submit their CAER exam forms to the OFA for “certification,” all CAER exam data is collected for aggregate statistical purposes to provide information on trends in eye disease and breed susceptibility. Clinicians and students of ophthalmology as well as interested breed clubs, individual breeders and owners of specific breeds will find this useful.
Eye Disease Genetics
Genetic diseases are those that are passed on from parent to offspring through genes that carry the codes for each specific trait. Many of the diseases and disorders that affect the eyes have genetic factors.
How do we identify an inherited eye disease?
Although there are noteworthy exceptions, most of the ocular diseases of dogs presumed to be hereditary have not been adequately documented. Genetic studies require examination of large numbers of related animals in order to characterize the disorder (age of onset, characteristic appearance, rate of progression) and to define the mode of inheritance (recessive, dominant). In a clinical situation, related animals are frequently not available for examination once a disorder suspected as inherited is identified in an individual dog. Maintaining a number of dogs for controlled breeding trials through several generations is a long and costly process. Both of these obstacles are compounded by the fact that many ocular conditions do not develop until later in life. Until the genetic basis of an ocular disorder is defined in a peer-reviewed published report, we rely on what statistical information is available from registry organizations, informed opinions and consensus from ACVO diplomates. We must satisfy ourselves with terms like “presumed inherited” and “suspected to be inherited.” Several companies provide information on genetic testing and greatly assist in providing more information and data to aid in defining the canine genetics of ocular diseases.
There are eye diseases in the dog for which there is evidence of a genetic or heritable cause. The American College of Veterinary Ophthalmologists has listed ten of these diseases as automatic “fails” (this means the affected dog is ineligible to receive an eye certification) because of the significance of the condition to vision and/or the very strong evidence of heritability.
Portions of the material above have been reprinted with permission of the American College of Veterinary Ophthalmologists from the publication “Ocular Conditions Presumed to be Inherited in Purebred Dogs”, 5th Edition, 2010, produced by the Genetics Committee of the American College of Veterinary Ophthalmologists, © American College of Veterinary Ophthalmologists.
Eye Evaluation Criteria: What to Expect During the Exam
OFA Eye Certification examinations are screening exams performed by board certified veterinary ophthalmologists. The exams can take place either in the veterinary office or at a special clinic held in conjunction with another event (such as a dog show).
Bring your dog’s information to the exam so the exam form may be completed properly. Required information includes: registration number, owner’s name and contact information, dog’s registered name, date of birth, sex, breed/variety, and if applicable, permanent identification (via microchip or tattoo).
The exam is performed 30 to 40 minutes after pupil-dilating drops are placed in the eyes. The Eye Certification exam consists of indirect ophthalmoscopy and slit lamp biomicroscopy. It is not a comprehensive ocular health examination, but rather an eye screening exam. For example, Eye Certification exams do not entail measuring tear production, staining the eyes for the presence of corneal ulcers, or measuring intraocular pressures. Gonioscopy, tonometry, Schirmer tear test, electroretinography, and ultrasonography are not routinely performed; thus, dogs with goniodysgenesis, glaucoma, keratoconjunctivitis sicca, early lens luxation/subluxation or some early cases of progressive retinal atrophy might not be detected without further testing. If a serious ocular health problem (such as glaucoma) is suspected during the Eye Certification exam, the examiner will recommend a more comprehensive ocular examination. The diagnoses obtained during an OFA Companion Animal Eye Registry exam refer only to the observable phenotype (clinical appearance) of an animal. Thus it is possible for a clinically normal animal to be a carrier (abnormal genotype) of genetic abnormalities.
Yearly CERF Exams - Why Are They Important?
One of the most frequently asked questions at CERF is "Why is the CERF certification only valid for one year"? The reason is that some eye diseases in all breeds of dogs can occur at several ages. For example, if you take your dog to have a CERF examination when it is 8 weeks old, many diseases can be diagnosed. These diseases will not progress and once they have been diagnosed, they will not disappear or "go normal" in future examinations. These diseases include microphthalmos, iris coloboma, fundus staphyloma or coloboma, retinal detachment, persistent hyaloid artery, PHPV/PTVL, optic nerve coloboma, optic nerve hypoplasia, and micropapilla. Other diseases may be present at 8 to 10 weeks of age and these diseases can change in their appearance (get worse or better) or disappear with age. These include entropion and other eyelid conformational abnormalities, persistent pupillary membranes, retinal dysplasia (folds and geographic lesions), and choroidal hypoplasia. Still other diseases may not be diagnosed until the dog is older. Most hereditary cataracts do not form in the eye until dogs are 6 months to 8 years old. Progressive retinal atrophy is most commonly diagnosed in dogs that are 2 to 8 years of age, depending on the breed. The result is that a dog could be certified by CERF at 8 weeks and again as a 1 year old, and then not pass the CERF exam at 2 years of age because cataracts had appeared between the 1 and 2 year examination.
So, what does this mean to the breeder? Dogs should be certified every year to ensure that they have not developed serious ocular diseases that occur after dogs are one or 2 years old, such as cataracts or retinal atrophy. A yearly normal CERF exam would keep the dog’s CERF number up-to-date. Individual dogs that are "clear" at their CERF exam at 9 years of age are usually not going to develop any genetic eye disease after 9 years. This is not completely true for every breed, however, it can be used as a general recommendation. My advice for show, obedience, performance, working and breeding dogs is that they have a CERF examination when they are young (< 4 months old), and another examination before they are used for breeding the first time. After that, males that are being used regularly for stud service should be examined every year until they are 10 years of age, and females and males that are being bred intermittently should be examined before they are bred each time. Having the exam as close to the breeding as possible decreases the possibility that a genetic disease has appeared and will be missed before breeding again. Many females only have a litter every other year, and while a CERF exam from 11 months ago is still valid, it is not as useful to the breeder as an exam that is normal in the month before breeding. It is equally important to check the validity of the CERF number of the dog you are breeding your dog with. Many breeders accept the word of other breeders that their CERF clearance is current. It is easy to check the date of the CERF examination on the VMDB/CERF website where the exam date is listed, along with the CERF certification number (http://www.VMDB.org). The CERF certificate also shows the year of the examination and the dogs age at examination, so you should ask to see the current certificate if you have not verified it from the website.
While yearly examinations do not guarantee that the dog is not a carrier of genetic ocular disease, they do ensure that within the last year, the dog was examined and no genetic ocular disease was diagnosed. If CERF clear dogs are bred, genetic ocular disease can be significantly decreased in each successive generation and eliminated in 6 generations.